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1
Arnheim, Katharina. "Erhaltungstherapie als Alternative zur Stammzelltransplantation." Onkologische Welt 09, no. 02 (April 2018): 77–78. http://dx.doi.org/10.1055/s-0038-1649313.
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Die Therapie mit dem bispezifischen Antikörper-Konstrukt Blinatumumab wurde in der TOWER-Studie bei rezidivierten und refraktären Patienten mit Philadelphia-Chromosom-negativer (Ph-) B-Vorläufer-ALL (Akute Lymphatische Leukämie) erfolgreich geprüft. Eine neue Auswertung der Studie zeigt jetzt, dass die Erhaltungstherapie mit Blimatumumab nach Erreichen einer kompletten hämatologischen Remission (CHR) für nicht stammzelltransplantierte Patienten aufgrund der Verlängerung des Gesamtüberlebens (OS) vorteilhaft ist.
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Schmale, Ine. "ASH 2019: Akute lymphatische Leukämie." Onkologische Welt 11, no. 01 (March 2020): 45–46. http://dx.doi.org/10.1055/a-1091-5756.
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Die Tiefe des Ansprechens, definiert durch die minimale Resterkrankung (MRD), erreicht innerhalb der hämatologischen malignen Erkrankungen einen immer höheren Stellenwert und wurde vielfach beim vergangenen ASH diskutiert. Sie ist auch ein Prädiktor für die Prognose von Patienten mit Philadelphia- Chromosom-positiver (Ph +) akuter lymphatischer Leukämie (ALL), wie in Orlando Ende 2019 gezeigt wurde. Eine Vertiefung der MRD wurde bei pädiatrischen B-ALL-Patienten mit dem neuen Standard Blinatumomab erreicht.
3
Wulff, K., and F. H. Herrmann. "Gerinnungsfaktoren VII, VIII, IX und X." Hämostaseologie 24, no. 02 (2004): 94–107. http://dx.doi.org/10.1055/s-0037-1619618.
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ZusammenfassungIn einer Übersicht werden einige molekulargenetische Aspekte der Gerinnungsfaktoren VII, VIII, IX und X dargestellt. Das Spektrum der Mutationen wird charakterisiert, das zu den genetisch bedingten Defekten Hämophilie A und B, Faktor-VII- und -X-Mangel führt. Für die Hämophilien A und B wird der genetische Beratung auf der Grundlage des X-chromosomalen Erbganges und der indirekten und direkten genomischen Analyse an ausgewählten Beispielen vorgestellt.Die Gene der Vitamin-K-abhängigen Serinproteasen Faktor VII und Faktor X sind auf dem Chromosom 13 lokalisiert. Mutationen führen zu autosomal-rezessiv vererbtem Faktor-VII- oder Faktor-X-Mangel. Das Mutationspektrum, die Rolle von Polymorphismen der Gene und das Spektrum der spontanen Blutungen dieser seltenen Blutungsleiden werden charakterisiert und Genotyp-Phänotyp-Korrelationen aufgezeigt.
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Zhao, J. T., M. Frommer, J. A. Sved, and A. Zacharopoulou. "Mitotic and polytene chromosome analyses in the Queensland fruit fly, Bactrocera tryoni (Diptera: Tephritidae)." Genome 41, no. 4 (August 1, 1998): 510–26. http://dx.doi.org/10.1139/g98-053.
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The Queensland fruit fly, Bactrocera tryoni, like the Mediterranean fruit fly, Ceratitis capitata, has a diploid complement of 12 chromosomes, including five pairs of autosomes and a XX/XY sex chromosome pair. Characteristic features of each chromosome are described. Chromosomal homology between B. tryoni and C. capitata has been determined by comparing chromosome banding pattern and in situ hybridisation of cloned genes to polytene chromosomes. Although the evidence indicates that a number of chromosomal inversions have occurred since the separation of the two species, synteny of the chromosomes appears to have been maintained.Key words: tephritid fruit fly, Bactrocera tryoni, polytene chromosomes, in situ hybridisation, chromosomal homology.
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Uno, Yoshinobu, Chizuko Nishida, Chiyo Takagi, Takeshi Igawa, Naoto Ueno, Masayuki Sumida, and Yoichi Matsuda. "Extraordinary Diversity in the Origins of Sex Chromosomes in Anurans Inferred from Comparative Gene Mapping." Cytogenetic and Genome Research 145, no. 3-4 (2015): 218–29. http://dx.doi.org/10.1159/000431211.
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Sex determination in frogs (anurans) is genetic and includes both male and female heterogamety. However, the origins of the sex chromosomes and their differentiation processes are poorly known. To investigate diversity in the origins of anuran sex chromosomes, we compared the chromosomal locations of sex-linked genes in 4 species: the African clawed frog (Xenopus laevis), the Western clawed frog (Silurana/X. tropicalis), the Japanese bell-ring frog (Buergeria buergeri), and the Japanese wrinkled frog (Rana rugosa). Comparative mapping data revealed that the sex chromosomes of X. laevis, X. tropicalis and R. rugosa are different chromosome pairs; however, the sex chromosomes of X. tropicalis and B. buergeri are homologous, although this may represent distinct evolutionary origins. We also examined the status of sex chromosomal differentiation in B. buergeri, which possesses heteromorphic ZW sex chromosomes, using comparative genomic hybridization and chromosome painting with DNA probes from the microdissected W chromosome. At least 3 rearrangement events have occurred in the proto-W chromosome: deletion of the nucleolus organizer region and a paracentric inversion followed by amplification of non-W-specific repetitive sequences.
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Çelik, Mustafa, Yavuz Bağcı, Esra Martin, and Halil Eroğlu. "Karyotype analysis and karyological relationships of Turkish Bunium species (Apiaceae)." Archives of Biological Sciences 72, no. 2 (2020): 203–9. http://dx.doi.org/10.2298/abs200122014c.
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Chromosomal data and karyological relationships provide valuable information about karyotype evolution and speciation. For the genus Bunium, the chromosomal data are limited. In the present study, the chromosomal data of 10 taxa are provided, 6 of which are given for the first time, 2 present new chromosome numbers, and 2 agree with previous reports. Four different chromosome numbers (2n=18, 20, 22 and 40) were detected, and 2n=40 is a new number in the genus Bunium. B. brachyactis is the first polyploid species of the genus with a ploidy level of 4x. The most asymmetric karyotypes are those of B. pinnatifolium and B. sayae. Regarding karyological relationships, B. pinnatifolium forms a monophyletic group by quite different karyological features such as large chromosomes, more submedian chromosomes and the most asymmetric karyotypes. In addition, the other 5 taxa form a strong monophyletic group. B. verruculosum and B. ferulaceum are cytotaxonomically very close species, as are B. sayae and B. elegans var. elegans. The chromosome numbers of 2 Turkish species, B. nudum and B. sivasicum, remain unknown. The presented results provide important contributions to the cytotaxonomy of Bunium.
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Milani, Diogo, Vanessa Bardella, Ana Ferretti, Octavio Palacios-Gimenez, Adriana Melo, Rita Moura, Vilma Loreto, Hojun Song, and Diogo Cabral-de-Mello. "Satellite DNAs Unveil Clues about the Ancestry and Composition of B Chromosomes in Three Grasshopper Species." Genes 9, no. 11 (October 26, 2018): 523. http://dx.doi.org/10.3390/genes9110523.
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Supernumerary (B) chromosomes are dispensable genomic elements occurring frequently among grasshoppers. Most B chromosomes are enriched with repetitive DNAs, including satellite DNAs (satDNAs) that could be implicated in their evolution. Although studied in some species, the specific ancestry of B chromosomes is difficult to ascertain and it was determined in only a few examples. Here we used bioinformatics and cytogenetics to characterize the composition and putative ancestry of B chromosomes in three grasshopper species, Rhammatocerus brasiliensis, Schistocerca rubiginosa, and Xyleus discoideus angulatus. Using the RepeatExplorer pipeline we searched for the most abundant satDNAs in Illumina sequenced reads, and then we generated probes used in fluorescent in situ hybridization (FISH) to determine chromosomal position. We used this information to infer ancestry and the events that likely occurred at the origin of B chromosomes. We found twelve, nine, and eighteen satDNA families in the genomes of R. brasiliensis, S. rubiginosa, and X. d. angulatus, respectively. Some satDNAs revealed clustered organization on A and B chromosomes varying in number of sites and position along chromosomes. We did not find specific satDNA occurring in the B chromosome. The satDNAs shared among A and B chromosomes support the idea of putative intraspecific ancestry from small autosomes in the three species, i.e., pair S11 in R. brasiliensis, pair S9 in S. rubiginosa, and pair S10 in X. d. angulatus. The possibility of involvement of other chromosomal pairs in B chromosome origin is also hypothesized. Finally, we discussed particular aspects in composition, origin, and evolution of the B chromosome for each species.
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Konerat, Jocicléia Thums, Vanessa Bueno, Lucas Baumgartner, Isabel Cristina Martins-Santos, and Vladimir Pavan Margarido. "B chromosome and NORs polymorphism in Callichthys callichthys (Linnaeus, 1758) (Siluriformes: Callichthyidae) from upper Paraná River, Brazil." Neotropical Ichthyology 12, no. 3 (June 23, 2014): 603–9. http://dx.doi.org/10.1590/1982-0224-20130189.
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B chromosomes are extra chromosomes from the normal chromosomal set, found in different organisms, highlighting their presence on the group of fishes. Callichthys callichthys from the upper Paraná River has a diploid number of 56 chromosomes (26 m-sm + 30 st-a) for both sexes, with the presence of a sporadically acrocentric B chromosome. Moreover, one individual presented a diploid number of 57 chromosomes, with the presence of a morphologically ill-defined acrocentric B chromosome in all analyzed cells. The physical mapping of 5S and 18S rDNA shows multiple 5S rDNA sites and only one pair of chromosomes with 18S sites in C. callichthys, except for two individuals. These two individuals presented a third chromosome bearing NORs (Ag-staining and 18S rDNA) where 5S and 18S rDNA genes are syntenic, differing only in position. The dispersion of the 18S rDNA genes from the main st-achromosome pair 25 to one of the chromosomes from the m-sm pair 4 would have originated two variant individuals, one of which with the ill-defined acrocentric B chromosome. Mechanisms to justify the suggested hypothesis about this B chromosome origin are discussed in the present study.
9
Malimpensa, Geovana C., Josiane B. Traldi, Danyelle Toyama, Flávio Henrique-Silva, Marcelo R. Vicari, and Orlando Moreira-Filho. "Chromosomal Mapping of Repeat DNA in Bergiaria westermanni (Pimelodidae, Siluriformes): Localization of 45S rDNA in B Chromosomes." Cytogenetic and Genome Research 154, no. 2 (2018): 99–106. http://dx.doi.org/10.1159/000487652.
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The occurrence of repetitive DNA in autosomes and B chromosomes of Bergiaria westermanni was examined using conventional and molecular cytogenetic techniques. This species exhibited 2n = 56 chromosomes, with intra- and interindividual variation in the number of heterochromatic B chromosomes (from 0 to 4). The 5S rDNA was localized in pairs 1 and 5, and histone probes (H1, H3, and H4) and U2 small nuclear RNA were syntenic with 5S rDNA in pair 5. Histone sequences were also located in chromosome pair 14. The (GATA)n sequence was dispersed throughout the autosomes and B chromosomes, with clusters (microsatellite accumulation) in some chromosome regions. The telomeric probe revealed no signs of chromosomal rearrangements in the genome of B. westermanni. The 45S rDNA sites were detected in the terminal region of pair 27; these sites corresponded to a GC-rich heterochromatin block. In addition, 3 of the 4 B chromosomes also contained 45S rDNA copies. Silver nitrate staining in interphase nuclei provided indirect evidence of the expression of these rRNA genes in B chromosomes, indicating the probable origin of these elements. This report shows plasticity in the chromosomal localization of repeat DNA in B. westermanni and features a discussion of genomic diversification.
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Albert, Patrice S., Tao Zhang, Kassandra Semrau, Jean-Marie Rouillard, Yu-Hsin Kao, Chung-Ju Rachel Wang, Tatiana V. Danilova, Jiming Jiang, and James A. Birchler. "Whole-chromosome paints in maize reveal rearrangements, nuclear domains, and chromosomal relationships." Proceedings of the National Academy of Sciences 116, no. 5 (January 17, 2019): 1679–85. http://dx.doi.org/10.1073/pnas.1813957116.
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Whole-chromosome painting probes were developed for each of the 10 chromosomes of maize by producing amplifiable libraries of unique sequences of oligonucleotides that can generate labeled probes through transcription reactions. These paints allow identification of individual homologous chromosomes for many applications as demonstrated in somatic root tip metaphase cells, in the pachytene stage of meiosis, and in interphase nuclei. Several chromosomal aberrations were examined as proof of concept for study of various rearrangements using probes that cover the entire chromosome and that label diverse varieties. The relationship of the supernumerary B chromosome and the normal chromosomes was examined with the finding that there is no detectable homology between any of the normal A chromosomes and the B chromosome. Combined with other chromosome-labeling techniques, a complete set of whole-chromosome oligonucleotide paints lays the foundation for future studies of the structure, organization, and evolution of genomes.
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Boroń, Alicja, Anna Grabowska, Aneta Spóz, and Anna Przybył. "B Chromosomes and Cytogenetic Characteristics of the Common Nase Chondrostoma nasus (Linnaeus, 1758)." Genes 11, no. 11 (November 6, 2020): 1317. http://dx.doi.org/10.3390/genes11111317.
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Supernumerary B chromosomes (Bs) are very promising structures, among others, in that they are an additional genomic compartment for evolution. In this study, we tested the presence and frequency of B chromosomes and performed the first cytogenetic examination of the common nase (Chondrostoma nasus). We investigated the individuals from two populations in the Vistula River basin, in Poland, according to the chromosomal distribution of the C-bands and silver nucleolar organizer regions (Ag-NORs), using sequential staining with AgNO3 and chromomycin A3 (CMA3). Furthermore, we analyzed the chromosomal localization of two rDNA families (45S and 5S rDNA) using fluorescence in situ hybridization (FISH) with rDNA probes. Chondrostoma nasus individuals showed a standard (A) chromosome set consisting of 2n = 50: 12 metacentric, 32 submetacentric, and 6 acrocentric chromosomes (NF = 94). Fourteen out of the 20 analyzed individuals showed 1–2 mitotically unstable submetacentric B chromosomes of different sizes. Six of them, in 14.1% of the analyzed metaphase plates, had a single, medium-sized submetacentric B (Bsm) chromosome (2n = 51) with a heterochromatic block located in its pericentromeric region. The other seven individuals possessed a Bsm (2n = 51) in 19.4% of the analyzed metaphase plates, and a second Bsm chromosome (2n = 52), the smallest in the set, in 15.5% of metaphase plates, whereas one female was characterized by both Bsm chromosomes (2n = 52) in 14.3% of the analyzed metaphase plates. AgNORs, GC-rich DNA sites, and 28S rDNA hybridization sites were observed in the short arms of two submetacentric chromosome pairs of A set. The constitutive heterochromatin was visible as C bands in the centromeric regions of almost all Chondrostoma nasus chromosomes and in the pericentromeric region of several chromosome pairs. Two 5S rDNA hybridization sites in the pericentromeric position of the largest acrocentric chromosome pair were observed, whereas two other such sites in co-localization on a smaller pair of NOR chromosomes indicate a species-specific character. The results herein broaden our knowledge in the field of B chromosome distribution and molecular cytogenetics of Chondrostoma nasus: a freshwater species from the Leuciscidae family.
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Favarato, Ramon M., Leila Braga Ribeiro, Rafaela P. Ota, Celeste M. Nakayama, and Eliana Feldberg. "Cytogenetic Characterization of Two Metynnis Species (Characiformes, Serrasalmidae) Reveals B Chromosomes Restricted to the Females." Cytogenetic and Genome Research 158, no. 1 (2019): 38–45. http://dx.doi.org/10.1159/000499954.
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Karyotypes and chromosomal characteristics with focus on B chromosomes of 2 species of the serrasalmid genus Metynnis, namely M. lippincottianus and M. maculatus, were examined using conventional (C-banding) and molecular (FISH mapping of minor and major rDNAs and Rex1, Rex3, and Rex6 retrotransposable elements) protocols. Both species possessed a diploid chromosome number of 2n = 62 and karyotypes composed of 32 metacentric + 28 submetacentric + 2 subtelocentric and 32 metacentric + 26 submetacentric + 4 subtelocentric, respectively; one small B element was found in the female genome of M. lippincottianus. C-banding revealed heterochromatin in the pericentromeric and terminal portions of all chromosomes of both species; the B chromosome was entirely heterochromatic. FISH showed 18S rDNA sites in 2 chromosome pairs in both species (pairs 19 and 22), and a large block in the B chromosome, while 5S rDNA signals were detected in the first pair of subtelocentric chromosomes in both species, moreover in M. maculatus an additional labeled pair 4 was observed. Mapping of the Rex1, Rex3, and Rex6 retrotransposable elements in the genomes of M. lippincottianus and M. maculatus indicated that they were dispersed throughout nearly all the chromosomes of the complement, except for the B chromosome of M. lippincottianus.
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González-Sánchez, Mónica, Marcela Rosato, Mauricio Chiavarino, and María J. Puertas. "Chromosome Instabilities and Programmed Cell Death in Tapetal Cells of Maize With B Chromosomes and Effects on Pollen Viability." Genetics 166, no. 2 (February 1, 2004): 999–1009. http://dx.doi.org/10.1093/genetics/166.2.999.
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Abstract B chromosomes (B’s), knobbed chromosomes, and chromosome 6 (NOR) of maize undergo nondisjunction and micronucleus formation in binucleate tapetal cells. These chromosome instabilities are regular events in the program of tapetal cell death, but the B’s strongly increase A chromosome instability. We studied 1B and 0B plants belonging to selected lines for high or low B transmission rate and their F1 hybrids. These lines are characterized by meiotic conservation or loss of B chromosomes, respectively. The female B transmission (fBtl) allele(s) for low B transmission is dominant, inducing micronucleus formation and B nondisjunction. We hypothesize that the fBtl allele(s) induces knob instability. This instability would be sufficient to produce B loss in both meiocytes and binucleate tapetal cells. B instability could, in turn, produce instabilities in all chromosomes of maize complement. To establish whether the chromosomal instabilities are related to the tapetal programmed cell death (PCD) process, we applied the TUNEL technique. PCD, estimated as the frequency of binucleate tapetal cells with TUNEL label, was significantly correlated with the formation of micronuclei and the frequency of pollen abortion. It can be concluded that the observed chromosome instabilities are important to the PCD process and to the development of microspores to form viable pollen grains.
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Li, J., D. L. Klindworth, F. Shireen, X. Cai, J. Hu, and S. S. Xu. "Molecular characterization and chromosome-specific TRAP-marker development for Langdon durum D-genome disomic substitution lines." Genome 49, no. 12 (December 2006): 1545–54. http://dx.doi.org/10.1139/g06-114.
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The aneuploid stocks of durum wheat ( Triticum turgidum L. subsp. durum (Desf.) Husnot) and common wheat ( T. aestivum L.) have been developed mainly in ‘Langdon’ (LDN) and ‘Chinese Spring’ (CS) cultivars, respectively. The LDN-CS D-genome chromosome disomic substitution (LDN-DS) lines, where a pair of CS D-genome chromosomes substitute for a corresponding homoeologous A- or B-genome chromosome pair of LDN, have been widely used to determine the chromosomal locations of genes in tetraploid wheat. The LDN-DS lines were originally developed by crossing CS nulli-tetrasomics with LDN, followed by 6 backcrosses with LDN. They have subsequently been improved with 5 additional backcrosses with LDN. The objectives of this study were to characterize a set of the 14 most recent LDN-DS lines and to develop chromosome-specific markers, using the newly developed TRAP (target region amplification polymorphism)-marker technique. A total of 307 polymorphic DNA fragments were amplified from LDN and CS, and 302 of them were assigned to individual chromosomes. Most of the markers (95.5%) were present on a single chromosome as chromosome-specific markers, but 4.5% of the markers mapped to 2 or more chromosomes. The number of markers per chromosome varied, from a low of 10 (chromosomes 1A and 6D) to a high of 24 (chromosome 3A). There was an average of 16.6, 16.6, and 15.9 markers per chromosome assigned to the A-, B-, and D-genome chromosomes, respectively, suggesting that TRAP markers were detected at a nearly equal frequency on the 3 genomes. A comparison of the source of the expressed sequence tags (ESTs), used to derive the fixed primers, with the chromosomal location of markers revealed that 15.5% of the TRAP markers were located on the same chromosomes as the ESTs used to generate the fixed primers. A fixed primer designed from an EST mapped on a chromosome or a homoeologous group amplified at least 1 fragment specific to that chromosome or group, suggesting that the fixed primers might generate markers from target regions. TRAP-marker analysis verified the retention of at least 13 pairs of A- or B-genome chromosomes from LDN and 1 pair of D-genome chromosomes from CS in each of the LDN-DS lines. The chromosome-specific markers developed in this study provide an identity for each of the chromosomes, and they will facilitate molecular and genetic characterization of the individual chromosomes, including genetic mapping and gene identification.
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Zadesenets, K. S., and N. B. Rubtsov. "Regions enriched for DNA repeats in chromosomes of Macrostomum mirumnovem, a species with a recent Whole Genome Duplication." Vavilov Journal of Genetics and Breeding 24, no. 6 (October 28, 2020): 636–42. http://dx.doi.org/10.18699/vj20.657.
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The free-living flatworm Macrostomum mirumnovem is a neopolyploid species whose genome underwent a recent Whole Genome Duplication (WGD). In the result of chromosome fusions of the ancient haploid chromosome set, large metacentric chromosomes were formed. In addition to three pairs of small metacentrics, the current karyotype of M. mirumnovem contains two pairs of large metacentric chromosomes, MMI1 and MMI2. The generation of microdissected DNA libraries enriched for DNA repeats followed by DNA probe preparation and fluorescent in situ hybridization (FISH) were performed. The DNA probes obtained marked chromosome regions enriched for different DNA repeats in the M. mirumnovem chromosomes. The size and localization of these regions varied in different copies of large chromosomes. They varied even in homologous chromosomes, suggesting their divergence due to genome re-diploidization after a WGD. Besides the newly formed chromosome regions enriched for DNA repeats, B chromosomes were found in the karyotypes of the studied specimens of M. mirumnovem. These B chromosomes varied in size and morphology. FISH with microdissected DNA probes revealed that some Bs had a distinct DNA content. FISH could paint differently B chromosomes in different worms and even in the same sample. B chromosomes could carry a bright specific fluorescent signal or could show no fluorescent signal at all. In latter cases, the specific FISH signal could be absent even in the pericentromeric region of the B chromosome. Possible mechanisms of B chromosome formation and their further evolution are discussed. The results obtained indicate an important role that repetitive DNAs play in genome re-diploidization initiating a rapid differentiation of large chromosome copies. Taking together, karyotype peculiarities (a high level of intraspecific karyotypic diversity associated with chromosome number variation, structural chromosomal rearrangements, and the formation of new regions enriched for DNA repeats) and some phenotypic features of M. mirumnovem (small body size, short lifecycle, easy maintenance in the laboratory) make this species a perspective model in the studies of genomic and karyotypic evolution in species passed through a recent WGD event.
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Baimai, V., W. Trinachartvanit, P. J. Grote, U. Kijchalao, S. Tigvattananont, and R. Poramarcom. "Metaphase karyotypes of fruit flies of Thailand. I. Five sibling species of the Bactrocera dorsalis complex." Genome 38, no. 5 (October 1, 1995): 1015–22. http://dx.doi.org/10.1139/g95-134.
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Natural populations of fruit flies of the Bactrocera dorsalis complex exhibit chromosomal variation based on differences in the amount and distribution of constitutive heterochromatin in the centromeric regions of the autosomes and the sex chromosomes. The chromosomal variation, coupled with differences in external morphology and host plant specific preferences, strongly suggest the existence of 5 closely related species within the B. dorsalis complex that have provisionally been designated B. dorsalis species B, C, D, and E in contrast with B. dorsalis s.s. (species A). Analysis of heterochromatin in autosomes and sex chromosomes has revealed 4 distinct groups of mitotic karyotypes. Bactrocera dorsalis is the only representative of Group I, which is characterized by the typical metacentric X chromosome and major blocks of centromeric heterochromatin in autosomes 5 and 6. Group 2 consists of species B and C, which show prominent landmarks of pericentric heterochromatin in all autosomes and in the X chromosome. Group 3 comprises species D, which is characterized by conspicuous blocks of pericentric heterochromatin in all autosomes but the long arm of the subtelocentric X chromosome is euchromatic and lacks a major portion of centromeric heterochromatin. Species E belongs to Group 4, which differs from Group 3 in having major blocks of heterochromatin at the distal portion of the X chromosome in addition to the prominent landmarks of pericentric heterochromatin in all autosomes. Chromosomal evolution among closely related species within the B. dorsalis complex clearly involves the presence or absence of constitutive heterochromatin in the centromeric regions of autosomes as well as in the X chromosome.Key words: Bactrocera dorsalis complex, metaphase karyotype, heterochromatin, chromosomal evolution.
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Blavet, Nicolas, Hua Yang, Handong Su, Pavel Solanský, Ryan N. Douglas, Miroslava Karafiátová, Lucie Šimková, et al. "Sequence of the supernumerary B chromosome of maize provides insight into its drive mechanism and evolution." Proceedings of the National Academy of Sciences 118, no. 23 (June 4, 2021): e2104254118. http://dx.doi.org/10.1073/pnas.2104254118.
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B chromosomes are enigmatic elements in thousands of plant and animal genomes that persist in populations despite being nonessential. They circumvent the laws of Mendelian inheritance but the molecular mechanisms underlying this behavior remain unknown. Here we present the sequence, annotation, and analysis of the maize B chromosome providing insight into its drive mechanism. The sequence assembly reveals detailed locations of the elements involved with the cis and trans functions of its drive mechanism, consisting of nondisjunction at the second pollen mitosis and preferential fertilization of the egg by the B-containing sperm. We identified 758 protein-coding genes in 125.9 Mb of B chromosome sequence, of which at least 88 are expressed. Our results demonstrate that transposable elements in the B chromosome are shared with the standard A chromosome set but multiple lines of evidence fail to detect a syntenic genic region in the A chromosomes, suggesting a distant origin. The current gene content is a result of continuous transfer from the A chromosomal complement over an extended evolutionary time with subsequent degradation but with selection for maintenance of this nonvital chromosome.
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Spies, J. J., E. Van der Merwe, H. Du Plessis, and E. J. L. Saayman. "Basic chromosome numbers and polyploid levels in some South African and Australian grasses (Poaceae)." Bothalia 21, no. 2 (October 15, 1991): 163–70. http://dx.doi.org/10.4102/abc.v21i2.882.
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Chromosome numbers of 46 specimens of grasses, involving 24 taxa from South Africa and Australia, have been determined during the present study. For the first time chromosome numbers are given for Eragrostis sarmentosa (Thunb.) Trin. (n = 20). Panicum aequinerve Nees (n = 18), Digitaria argyrograpta (Nees) Stapf (n = 9) and D. maitlandii Stapf C.E. Hubb. (n = 9). Additional polyploid levels are described for Diplachne fusca (L.) Beauv. ex Roem. Schult. (n = 10) and Digitaria diagonalis (Nees) Stapf var. diagonalis (n = 9).B-chromosomes were observed in several different specimens. The presence of B-chromosomes often results in abnormal chromosomal behaviour during meiosis.
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Ramírez, Corália CL, and Eliana MB Dessen. "Chromosomal evidence for sibling species of the malaria vector Anopheles cruzii." Genome 43, no. 1 (February 1, 2000): 143–51. http://dx.doi.org/10.1139/g99-103.
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An analysis of the ovarian polytene chromosomes of Anopheles cruzii from three localities in Southeast Brazil revealed the existence of two genetic entities within this morphologically uniform taxon. These cryptic species differed in the banding patterns of the X chromosome and 3L arm. A pattern of bands that cannot be explained by the fixation of any of the known inversions in chromosome X was revealed and named chromosomal form B to distinguish it from the standard pattern of this X chromosome, form A. Each chromosomal form is characterized by a different set of inversions. The lack of heterozygotes (A/B) for these X chromosome forms in populations where both forms coexist is evidence of absence or limited gene flow between the two groups. Key words: Anopheles cruzii, inversion polymorphism, sibling species.
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Rupp, Niels J., Axel Mischo, and Holger Moch. "Neue und vielversprechende molekulare Therapieoptionen in verschiedenen Subtypen des Nierenzellkarzinoms." Therapeutische Umschau 74, no. 4 (September 2017): 171–79. http://dx.doi.org/10.1024/0040-5930/a000901.
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Zusammenfassung. Nierenzellkarzinome bilden eine heterogene Gruppe von Karzinomen mit verschiedenen histologischen Subtypen. Die Mehrheit der Nierenzellkarzinome beim Erwachsenen sind klarzellige Nierenzellkarzinome (ccRCC), welche durch Alterationen im von Hippel-Lindau (VHL) Gen charakterisiert sind. Neue Erkenntnisse zeigen dabei die genetische Heterogenität dieser Entität und das Vorhandensein von mindestens drei zusätzlichen ccRCC Tumorsuppressorgenen auf dem Chromosom 3p. Aufgrund der Inaktivierung von VHL produzieren die Nierenzellkarzinomzellen den auf Hypoxia Inducible Factor (HIF) reagierenden Wachstumsfaktor vascular endothelial growth factor (VEGF). Die neuen systemischen Therapien, inklusive Tyrosinkinasehemmer, monoklonale Antikörper und mTOR-Inhibitoren zielen darauf ab, die Angiogenese zu inhibieren, indem sie die VEGF Wirkung inhibieren. In Nierenzellkarzinomen, die mit erblichen Tumorsyndromen assoziiert sein können bzw. dort initial beschrieben wurden, sind spezifische Genaberrationen identifiziert worden, z. B. in den Genen FLCN, TFE3, TFEB, MITF, FH, SDHB, SDHD und MET. Diese Arbeit soll eine Übersicht über die Fortschritte in der molekularen Therapie des metastasierten ccRCC geben und zusätzlich auf Genese, Prognose und potenzielle zielgerichtete Therapien weiterer morphologisch und molekular definierter Nierenzellkarzinome eingehen.
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Cuadrado, Angeles, Milena Cardoso, and Nicolás Jouve. "Increasing the physical markers of wheat chromosomes using SSRs as FISH probes." Genome 51, no. 10 (October 2008): 809–15. http://dx.doi.org/10.1139/g08-065.
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In plants the marker sequences used to identify chromosomes are mainly repetitive DNA probes. Simple sequence repeats (SSRs) are major components of many plant genomes and could be good markers for chromosome identification. In a previous work, we reported the physical distribution of 4 oligonucleotides, (AG)12, (CAT)5, (AAC)5, and (AAG)5, on Triticum aestivum L. chromosomes. The distinctive distribution pattern found suggested that SSR in situ hybridization is useful as a diagnostic tool in wheat cytogenetics. To check whether that finding is generally applicable, we analyzed the chromosomal distribution of the rest of the 14 possible classes of di- and tri-nucleotide repeats by FISH. A detailed knowledge of the sequence content of hexaploid wheat chromatin was acquired based on the hybridization signals, which also provide a rich set of chromosome markers for chromosome identification. Except for (AT)10 and (GC)10, for which the chromosomal distribution could not be accurately determined, and (AC)8 and (GCC)5, which were found dispersed throughout the chromosomes, the remaining repeats were observed as clusters on specific chromosome sites. (AGG)5, (CAC)5, (ACG)5, (AAT)5, and (CAG)5 exhibited a preferential distribution in the pericentromeric regions of the B genome chromosomes. The richest patterns of intercalary signals on several A and B genome chromosomes were produced by (ACT)5. A karyotype based on the SSR probes providing the best FISH patterns was constructed for T. aestivum ‘Chinese Spring’.
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Drosopoulou, Elena, Ifigeneia Nakou, and Penelope Mavragani-Tsipidou. "The Bactrocera oleae genome: localization of nine genes on the polytene chromosomes of the olive fruit fly (Diptera: Tephritidae)." Genome 57, no. 10 (October 2014): 573–76. http://dx.doi.org/10.1139/gen-2014-0172.
Full textAbstract:
Four homologous and five heterologous gene-specific sequences have been mapped by in situ hybridization on the salivary gland polytene chromosomes of the olive fruit fly, Bactrocera oleae. The nine genes were dispersed on four of the five autosomal chromosomes, thus enriching the available set of chromosome landmarks for this major agricultural pest. Present data further supports the proposed chromosome homologies among B. oleae, Ceratitis capitata, and Drosophila melanogaster and the idea of the conservation of chromosomal element identity throughout dipteran evolution.
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Zhang, Daming, and Tao Sang. "Chromosomal structural rearrangement of Paeonia brownii and P. californica revealed by fluorescence in situ hybridization." Genome 41, no. 6 (December 1, 1998): 848–53. http://dx.doi.org/10.1139/g98-079.
Full textAbstract:
Chromosomal structural rearrangement in Paeonia brownii and P. californica (2n = 10) was studied by in situ hybridization using 18S rDNA probes. Six major rDNA sites were detected in mitotic cells of P. californica; six major and two minor rDNA sites were found in P. brownii. Two cytotypes (A and B), with different chromosomal morphology and (or) rDNA locations, were observed in the population of P. californica. Cytotype A, with rDNA sites only on the short arms of chromosomes, was considered to be the normal cytotype. Both translocation and pericentric inversion may have occurred to give rise to cytotype B, in which one homolog of chromosome 4 has rDNA sites on both arms while its homolog has no rDNA sites; one homolog of chromosome 3 has a rDNA site on the long arm. Two rearranged cytotypes, C and D, were observed in the population of P. brownii. Given that the normal cytotype of P. brownii is most likely to have six major rDNA sites on the short arms of chromosomes 3, 4, and 5, and two minor sites on the short arms of chromosome 2, cytotype C may have resulted from a translocation between the short arm of one homolog of chromosome 2 and the long arm of one homolog of chromosome 4, and cytotype D may have resulted from a translocation between the short arm of one homolog of chromosome 3 and the long arm of one homolog of chromosome 4. These results supported previous observations, based on meiotic configurations, that chromosomal structural rearrangement occurred frequently in P. brownii and P. californica.Key words: chromosomal structural rearrangement, in situ hybridization, rDNA, translocation, pericentric inversion, Paeonia.
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KOKUBUGATA, G., K. D. HILL, G. W. WILSON, K. KONDO, and L. M. RANDALL. "A COMPARISON OF CHROMOSOME NUMBER AND KARYOTYPE IN SOMATIC CHROMOSOMES OF STANGERIACEAE (CYCADALES)." Edinburgh Journal of Botany 58, no. 3 (October 24, 2001): 475–81. http://dx.doi.org/10.1017/s0960428601000786.
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Somatic chromosomes at mitotic metaphase of two species and two undescribed populations of Bowenia, and Stangeria eriopus, which were classified in Stangeriaceae, Cycadales, were compared using the standard aceto-orcein staining method. All Bowenia taxa showed a chromosome number of 2n = 18, while S. eriopus showed a chromosome number of 2n = 16. The chromosome number of 2n = 18 in B. ‘Kuranda’ is reported for the first time. The present karyotype analysis indicates that B. ‘Kuranda’ and another undescribed taxon, B. ‘Tinaroo’, are cytotaxonomically closer to B. spectabilis than B. serrulata, and that the karyotype of Stangeria is unlikely to have been derived from that of Bowenia by a simple chromosomal change such as centromeric fission and deletion.
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Huang, Wai Mun, Margaret Robertson, John Aron, and Sherwood Casjens. "Telomere Exchange between Linear Replicons of Borrelia burgdorferi." Journal of Bacteriology 186, no. 13 (July 1, 2004): 4134–41. http://dx.doi.org/10.1128/jb.186.13.4134-4141.2004.
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ABSTRACT Spirochetes in the genus Borrelia carry a linear chromosome and numerous linear plasmids that have covalently closed hairpin telomeres. The overall organization of the large chromosome of Borrelia burgdorferi appears to have been quite stable over recent evolutionary time; however, a large fraction of natural isolates carry differing lengths of DNA that extend the right end of the chromosome between about 7 and 20 kbp relative to the shortest chromosomes. We present evidence here that a rather recent nonhomologous recombination event in the B. burgdorferi strain Sh-2-82 lineage has replaced its right chromosomal telomere with a large portion of the linear plasmid lp21, which is present in the strain B31 lineage. At least two successive rounds of addition of linear plasmid genetic material to the chromosomal right end appear to have occurred at the Sh-2-82 right telomere, suggesting that this is an evolutionary mechanism by which plasmid genetic material can become part of the chromosome. The unusual nonhomologous nature of this rearrangement suggests that, barring horizontal transfer, it can be used as a unique genetic marker for this lineage of B. burgdorferi chromosomes.
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Birchler, J. A., D. J. Chalfoun, and D. M. Levin. "Recombination in the B chromosome of maize to produce A-B-A chromosomes." Genetics 126, no. 3 (November 1, 1990): 723–33. http://dx.doi.org/10.1093/genetics/126.3.723.
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Abstract The translocations between the supernumerary B chromosomes and the normal A chromosomes of maize provide a valuable tool for gene localizations, dosage studies and characterization of mutants as null, leaky or gain-of-function. A procedure is described, that relies on recombination in the B chromosome, for marking each of the various B-A translocations with a single dominant marker that will allow dosage classifications of individuals at the mature kernel stage. This marker is R-scm3, which conditions anthocyanin pigment in the aleurone of the endosperm and the scutellum of the embryo. A test for recombination in the B chromosome was conducted by crossing together two translocations, that were broken on opposite sides of the B centromere, and in different A chromosome arms, namely TB-1La and TB-10L18. An example was recovered that linked genetic markers on 1L and 10L to the B centromere. Cytological examination at pachytene of meiosis confirmed the new chromosomal linkage. The use of this procedure to produce a comprehensive set of uniformly marked B-A translocations is discussed.
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Mariotto, Sandra, Liano Centofante, Carlos S. Miyazawa, Luiz Antonio Carlos Bertollo, and Orlando Moreira Filho. "Chromosome polymorphism in Ancistrus cuiabae Knaack, 1999 (Siluriformes: Loricariidae: Ancistrini)." Neotropical Ichthyology 7, no. 4 (2009): 595–600. http://dx.doi.org/10.1590/s1679-62252009000400006.
Full textAbstract:
Cytogenetic and FISH analyses were performed in 30 Ancistrus cuiabae specimens from a bay near the town of Poconé, in the Pantanal of Mato Grosso, Brazil. The observed diploid number was 2n = 34 chromosomes for both sexes and three distinct katyotypic formulae were found, namely cytotype A (20m, 8sm, 6st, Fundamental Number/FN = 68; 6 males and 11 females), cytotype B (19m, 8sm, 6st, 1a, FN = 67; 8 males and 4 females) and cytotype C (18m, 8sm, 6st, 2a, FN = 66; a single male). NORs's analyses showed that these regions were located in distinct sites on the NOR-bearing chromosome pair, according to cytotypes. Thus, in cytotype A, NORs were located in the terminal region of the short arm of the second metacentric chromosome pair; in cytotype B, they were detected in the short arm of the metacentric chromosome and interstitially on the acrocentric chromosome and, in cytotype C, NORs were observed in the interstitial region of the acrocentric chromosome pair. C-positive heterochromatic bands were adjacent to the rDNA sites in the corresponding chromosomes. Thus, the chromosomal polymorphism of A. cuiabae was probably originated through a pericentric inversion in chromosome pair nº 2 involving the NOR sites, which represents a novelty in the Ancistrini tribe. The results also broaden the knowledge of the chromosomal evolution in Ancistrus, the most derived genus of the Ancistrini tribe.
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Kaiser, P. E., J. A. Seawright, and B. K. Birky. "Chromosome polymorphism in natural populations of Anopheles quadrimaculatus Say species A and B." Genome 30, no. 2 (April 1, 1988): 138–46. http://dx.doi.org/10.1139/g88-024.
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Ovarian polytene chromosomes from eight populations of Anopheles quadrimaculatus in the southeastern United States were observed for chromosomal polymorphisms. Two sibling species, species A and B, each with intraspecific inversions, were distinguished. Species A correlates with the previously published standard maps for salivary gland and ovarian nurse-cell polytene chromosomes. Species A was found at all eight collection sites, and five of these populations also contained species B. Three inversions on the right arm of chromosome 3 were observed in species A. Species B contained a fixed inversion on the X chromosome, one fixed and one floating inversion on the left arm of chromosome 2, and one fixed and one floating inversion on the right arm of chromosome 3. The fixed inversion on the X chromosome makes this the best diagnostic chromosome for distinguishing species A and B. An unusual dimorphism in the left arm of chromosome 3, found in both species A and B, contained two inversions. The heterokaryotypes, as well as two distinct homokaryotypes, were seen in all of the field populations. Intraspecific clinal variations in the frequencies of the species A inversions were noted. The Florida populations were practically devoid of inversions, the Georgia and Alabama populations contained some inversions, and the Arkansas population was mostly homozygous for two of the inversions. The phylogenetic relationships of species A and B to the Maculipennis complex (Nearctic) are discussed.Key words: Anopheles, inversion, populations, chromosome polymorphism, phylogenetics.
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Gause, Maria, Ziva Misulovin, Amy Bilyeu, and Dale Dorsett. "Dosage-Sensitive Regulation of Cohesin Chromosome Binding and Dynamics by Nipped-B, Pds5, and Wapl." Molecular and Cellular Biology 30, no. 20 (August 9, 2010): 4940–51. http://dx.doi.org/10.1128/mcb.00642-10.
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ABSTRACT The cohesin protein complex holds sister chromatids together to ensure proper chromosome segregation upon cell division and also regulates gene transcription. Partial loss of the Nipped-B protein that loads cohesin onto chromosomes, or the Pds5 protein required for sister chromatid cohesion, alters gene expression and organism development, without affecting chromosome segregation. Knowing if a reduced Nipped-B or Pds5 dosage changes how much cohesin binds chromosomes, or the stability with which it binds, is critical information for understanding how cohesin regulates transcription. We addressed this question by in vivo fluorescence recovery after photobleaching (FRAP) with Drosophila salivary glands. Cohesin, Nipped-B, and Pds5 all bind chromosomes in both weak and stable modes, with residence half-lives of some 20 seconds and 6 min, respectively. Reducing the Nipped-B dosage decreases the amount of stable cohesin without affecting its chromosomal residence time, and reducing the Pds5 dosage increases the amount of stable cohesin. This argues that Nipped-B and Pds5 regulate transcription by controlling how much cohesin binds DNA in the stable mode, and not binding affinity. We also found that Nipped-B, Pds5, and the Wapl protein that interacts with Pds5 all play unique roles in cohesin chromosome binding.
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Tsunewaki, Koichiro. "Aneuploid analyses of hybrid necrosis and hybrid chlorosis in tetraploid wheats using the D genome chromosome substitution lines of durum wheat." Genome 35, no. 4 (August 1, 1992): 594–601. http://dx.doi.org/10.1139/g92-089.
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Chromosomal locations of the Ne1 gene, one of the two complementary genes for type 1 hybrid necrosis, and two complementary genes, Cs1 and Cs2, for type 2 hybrid chlorosis in tetraploid wheats were determined by aneuploid analyses employing the D genome chromosome substitution lines of 'Langdon' durum wheat. The Ne1 gene of 'Langdon' is located on chromosome 5B, whereas the Cs1 gene of Triticum dicoccum 'Hokudai' and the Cs2 gene of T. timopheevi are located on chromosomes 5A and 4G, respectively. Chromosomes 4B and 4G show almost complete functional compensation, though they rarely pair with each other, but chromosome 4D of T. aestivum 'Chinese Spring' has only half the ability of chromosome 4G in compensating for chromosome 4B on the fertilization ability of the male gamete. The results have demonstrated the usefulness of the D genome chromosome substitution lines of durum wheat for determining the chromosomes carrying major genes in tetraploid wheat. The results of these studies support the reallocation of chromosome 4A to the B genome.Key words: durum wheat, hybrid necrosis, hybrid chlorosis, aneuploid analyses, chromosome substitution lines.
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Schartl, M. "A sex chromosomal restriction-fragment-length marker linked to melanoma-determining Tu loci in Xiphophorus." Genetics 119, no. 3 (July 1, 1988): 679–85. http://dx.doi.org/10.1093/genetics/119.3.679.
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Abstract In Xiphophorus, the causative genetic information for melanoma formation has been assigned by classical genetics to chromosomal loci, which are located on the sex chromosomes. In our attempts to molecularly clone these melanoma-determining loci, named Tu, we have looked for restriction-fragment-length markers (RFLMs) linked to the Tu loci. These RFLMs should be useful in obtaining a physical map of a Tu locus, which will aid in the cloning of the corresponding sequences. DNA samples from various Xiphophorus strains and hybrids including those bearing different Tu wild-type, deletion and translocation chromosomes, were screened for the presence of random RFLMs using homologous or heterologous sequences as hybridization probes. We find an EcoRI restriction fragment which shows limited crosshybridization to the v-erb B gene--but not representing the authentic c-erb B gene of Xiphophorus--to be polymorphic with respect to different sex chromosomes. Linkage analysis revealed that a 5-kb fragment is linked to the Tu-Sd locus on the X chromosome, a 7-kb fragment is linked to the Tu-Sr locus on the Y chromosome, both of Xiphophorus maculatus, and that a 12-kb fragment is linked to the Tu-Li locus on the X chromosome of Xiphophorus variatus. Using different chromosomal mutants this RFLM has been mapped to a frequent deletion/translocation breakpoint of the X chromosome, less than 0.3 cM apart from the Tu locus.
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Blagojevic, Jelena, Vladimir Jovanovic, Tanja Adnadjevic, Ivana Budinski, and Mladen Vujosevic. "Chromosome status of marsh marigold, Caltha palustris L. (Ranunculaceae) from Serbia." Genetika 45, no. 3 (2013): 793–98. http://dx.doi.org/10.2298/gensr1303793b.
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Marsh marigold, Caltha palustris is distributed in the moist, temperate and cold regions of the Northern Hemisphere. This species exhibits considerable amount of intraspecific chromosomal diversity involving hybridization, polyploidy, aneuploidy and B chromosomes. Karyotype analyses of three mountain populations from Serbia were done for the first time. All samples were tetraploid (based number x=8) with 2n=32. In population from mountain Tara presence of one B chromosomes was detected. Tetraploid karyotype consists of 17 median-centromeric (m), 8 submedian-centromeric (sm), 7 subterminal-centromeric (st) chromosomes and one terminal-centromeric (t) B chromosome (2n= 17m+8sm+7st+1B). Studied populations in Serbia belong to the most common cytotype for this species in Europe.
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Weber, D., and T. Helentjaris. "Mapping RFLP loci in maize using B-A translocations." Genetics 121, no. 3 (March 1, 1989): 583–90. http://dx.doi.org/10.1093/genetics/121.3.583.
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Abstract Plants hypoploid for specific segments of each of the maize (Zea mays L.) chromosomes were generated using 24 different B-A translocations. Plants carrying each of the B-A translocations were crossed as male parents to inbreds, and sibling progeny hypoploid or not hypoploid for specific chromosomal segments were recovered. Genomic DNAs from the parents, hypoploid progeny, and nonhypoploid (euploid or hyperploid) progeny for each of these B-A translocations were digested with restriction enzymes, electrophoresed in agarose gels, blotted onto reusable nylon membranes, and probed with nick-translated, cloned DNA fragments which had been mapped previously by restriction fragment length polymorphism (RFLP) analysis to the chromosome involved in the B-A translocation. The chromosomal segment on our RFLP map which was uncovered by each of the B-A translocations was determined. This work unequivocally identified the short and long arms of each chromosome on this map, and it also identified the region on each chromosome which contains the centromere. Because the breakpoints of the B-a translocations were previously known on the cytological and the conventional genetic maps, this study also allowed this RFLP map to be more highly correlated with these maps.
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Carlson, Wayne R., and Robin R. Roseman. "Segmental duplication of distal chromosomal regions in maize." Genome 34, no. 4 (August 1, 1991): 537–42. http://dx.doi.org/10.1139/g91-083.
Full textAbstract:
A number of cytogenetic methods have been used to duplicate specific chromosomal segments in maize. However, most of these techniques do not produce heritably stable duplications. The absence of stable inheritance for a duplication means that stock maintenance is difficult and potential agricultural applications cannot be pursued. Two methods for producing stable segmental duplications in maize have been previously proposed. Both methods utilize translocations between the maize B chromosome and standard chromosomes (B–A translocations). One technique duplicates proximal chromosomal segments, while the other duplicates distal regions. The proximal-duplication method was tested earlier. The distal-duplication technique is analyzed here. Two homozygous distal duplications were constructed and tested for gametic transmission. The duplications were found to be heritably stable within the limits of the genetic and cytological tests that were employed.Key words: B chromosome, maize, duplication.
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Attia, T., and G. Röbbelen. "Cytogenetic relationship within cultivated Brassica analyzed in amphihaploids from the three diploid ancestors." Canadian Journal of Genetics and Cytology 28, no. 3 (June 1, 1986): 323–29. http://dx.doi.org/10.1139/g86-048.
Full textAbstract:
To investigate the factors controlling evolutionary differentiation within the genus Brassica, chromosome pairing in amphihaploids from crosses between the three elementary diploid species B. campestris (AA), B. oleracea (CC), and B. nigra (BB) was analyzed. The amphihaploid AC showed a high amount of pairing, while the two amphihaploids AB and BC, both including the genome of B. nigra, exhibited only low degrees of chromosome association. By the occurrence of tetra- and penta-valents, auto- as well as allo-syndetic pairing was demonstrated to exist in the AC amphihaploid. True homologous pairing between the genomes A and C was deduced from the occurrence of chromosomal interchange configurations. Although the genomes of B. oleracea and B. campestris are evolutionarily distinct, as shown by the different number and structure of their chromosomes, their close relationship is readily evident from the high level of pairing observed in the AC amphihaploids. On the other hand, the much lower pairing within the amphihaploids including the B genome is unexpected in view of the hypothesis of a common ancestor for all three of the cultivated Brassica diploids from an ancestral genome with x = 6 chromosomes. It is discussed whether B. nigra is indeed more distantly related to the two other species or whether this genome carries a suppressor of chromosome pairing.Key words: chromosome pairing, amphihaploids, evolutionary relations.
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Jones, G. H., J. A. F. Whitehorn, and S. M. Albini. "Ultrastructure of meiotic pairing in B chromosomes of Crepis capillaris. I. One-B and two-B pollen mother cells." Genome 32, no. 4 (August 1, 1989): 611–21. http://dx.doi.org/10.1139/g89-489.
Full textAbstract:
Chromosome pairing of a small metacentric B chromosome in Crepis capillaris has been studied by synaptonemal complex surface spreading of pollen mother cells containing either one or two B chromosomes. The B-chromosome axis, on average, represents about 8.7% of the axis length of the standard A-chromosome set, which is less than the corresponding values for DNA content (10.6%) and mitotic chromosome volume (13.6%). Single B chromosomes commonly undergo fold-back pairing to give a symmetrical hairpin loop, which supports earlier suggestions that this B chromosome is an isochromosome. Two B chromosomes may show interarm pairing, exclusively, or interchromosome pairing, exclusively, or combinations of the two. Near the centromeres pairing occurs preferentially between arms of the same chromosome, but chromosome ends show random association. Some B chromosomes show anomalous pairing configurations, which may reflect further orders of reverse repeats within arms or, alternatively, nonhomologous pairing. The period of B-chromosome pairing is confined almost exclusively to zygotene, when the standard A chromosomes are pairing, but within this period their pairing is delayed relative to the A set. Individual B chromosomes at zygotene contain from one to three separate synaptonemal complex segments. These are widely distributed within the chromosomes, mainly in distal and interstitial regions; pairing is delayed around the centromere.Key words: B chromosomes, isochromosomes, synaptonemal complex.
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Kowalski, S. P., T. H. Lan, K. A. Feldmann, and A. H. Paterson. "Comparative mapping of Arabidopsis thaliana and Brassica oleracea chromosomes reveals islands of conserved organization." Genetics 138, no. 2 (October 1, 1994): 499–510. http://dx.doi.org/10.1093/genetics/138.2.499.
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Abstract The chromosomes of Arabidopsis thaliana and Brassica oleracea have been extensively rearranged since the divergence of these species; however, conserved regions are evident. Eleven regions of conserved organization were detected, ranging from 3.7 to 49.6 cM in A. thaliana, spanning 158.2 cM (24.6%) of the A. thaliana genome, and 245 cM (29.9%) of the B. oleracea genome. At least 17 translocations and 9 inversions distinguish the genomes of A. thaliana and B. oleracea. In one case B. oleracea homoeologs show a common marker order, which is distinguished from the A. thaliana order by a rearrangement, indicating that the lineages of A. thaliana and B. oleracea diverged prior to chromosomal duplication in the Brassica lineage (for at least this chromosome). Some chromosomal segments in B. oleracea appear to be triplicated, indicating the need for reevaluation of a classical model for Brassica chromosome evolution by duplication. The distribution of duplicated loci mapped for about 13% of the DNA probes studied in A. thaliana suggests that ancient duplications may also have occurred in Arabidopsis. The degree of chromosomal divergence between A. thaliana and B. oleracea appears greater than that found in other confamilial species for which comparative maps are available.
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Sharbel, Timothy F., David M. Green, and Andreas Houben. "B-chromosome origin in the endemic New Zealand frog Leiopelma hochstetteri through sex chromosome devolution." Genome 41, no. 1 (February 1, 1998): 14–22. http://dx.doi.org/10.1139/g97-091.
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The endemic New Zealand frog Leiopelma hochstetteri has variable numbers of mitotically stable B chromosomes. To assess whether the B chromosomes were derived from the autosome complement, they were isolated by micromanipulation and their DNA amplified by degenerate oligonucleotide primed PCR. Southern hybridizations of B chromosome DNA probes to genomic DNA from males and females characterized by differing numbers of B chromosomes demonstrated that the B chromosomes were derived from the univalent W sex chromosome characteristic of North Island populations. The presence of homologous B chromosome specific sequences from geographically distinct populations indicates a single origin of the B chromosomes. Furthermore, a primitive homology shared by B chromosomes and the W sex chromosome from an ancestral WZ/ZZ karyotype, which is still present in frogs from Great Barrier Island, shows that the B chromosomes originated soon after the univalent W sex chromosome had originated. Sequence analysis revealed that B chromosome DNA is composed of repeat sequences and has the potential to form stable hairpin structures. The molecular dynamics of these structures may reflect an inherent propensity to undergo rapid change in nucleotide sequence and chromosome structure.
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Piscor, Diovani, and Patricia P. Parise-Maltempi. "Microsatellite Organization in the B Chromosome and A Chromosome Complement in Astyanax (Characiformes, Characidae) Species." Cytogenetic and Genome Research 148, no. 1 (2016): 44–51. http://dx.doi.org/10.1159/000444728.
Full textAbstract:
The organization of microsatellites in B and sex chromosomes has been linked to chromosomal evolution in a number of animal groups. Here, the chromosomal organizations of (CA)15, (GA)15, (CG)15, (GACA)4, and (GATA)8 microsatellites were examined in several Astyanax species with different diploid numbers: Astyanax mexicanus (2n = 50 + 1 B chromosome), A. altiparanae (2n = 50), A. marionae (2n = 48), A. fasciatus (2n = 46), and A. schubarti (2n = 36). The (CA)15 and (GA)15 microsatellites were dispersed across the chromosomes of A. altiparanae and A. fasciatus but were also observed as clusters (CA and GA for A. altiparanae, and CA for A. fasciatus). In A. marionae and A. schubarti, the (CA)15 and (GA)15 microsatellites were dispersed but were also observed as clustered signals and coincident with heterochromatic regions. In all 4 of these species, the (CG)15 and (GACA)4 microsatellites were dispersed across chromosomes, and the (GATA)8 microsatellite was co-localized with 5S rDNA. In A. mexicanus, the (CA)15, (GA)15, (CG)15, (GATA)8, and (GACA)4 microsatellites were weakly detected and dispersed across the chromosomes of the A complement. On the B chromosome, signals for the different microsatellites were weak, strong, absent, weak, and absent, respectively. The distribution of microsatellites and the locational relationship between microsatellites and 5S rDNA are discussed, and a possible evolutionary pathway is proposed for microsatellites in Astyanax.
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Gokhman, Vladimir E. "Chromosomes of parasitic wasps of the superfamily Chalcidoidea (Hymenoptera): An overview." Comparative Cytogenetics 14, no. 3 (August 25, 2020): 399–416. http://dx.doi.org/10.3897/compcytogen.v14i3.56535.
Full textAbstract:
An overview of the current knowledge of chromosome sets of the parasitoid superfamily Chalcidoidea is given. Karyotypes of approximately 240 members of this group, i.e. just above one percent of described species, are studied up to now. Techniques for obtaining and analyzing preparations of chalcid chromosomes are outlined, including the so-called “traditional” and “modern” methods of differential staining as well as fluorescence in situ hybridization (FISH). Among the Chalcidoidea, the haploid chromosome number can vary from n = 3 to n = 11, with a clear mode at n = 6 and a second local maximum at n = 10. In this group, most chromosomes are either metacentric or submetacentric, but acrocentrics and/or subtelocentrics also can predominate, especially within karyotypes of certain Chalcidoidea with higher chromosome numbers. The following main types of chromosomal mutations are characteristic of chalcid karyotypes: inversions, fusions, translocations, polyploidy, aneuploidy and B chromosome variation. Although karyotype evolution of this superfamily was mainly studied using phylogenetic reconstructions based on morphological and/or molecular characters, chromosomal synapomorphies of certain groups were also revealed. Taxonomic implications of karyotypic features of the Chalcidoidea are apparently the most important at the species level, especially among cryptic taxa.
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Nelson, J. C., M. E. Sorrells, A. E. Van Deynze, Y. H. Lu, M. Atkinson, M. Bernard, P. Leroy, J. D. Faris, and J. A. Anderson. "Molecular mapping of wheat: major genes and rearrangements in homoeologous groups 4, 5, and 7." Genetics 141, no. 2 (October 1, 1995): 721–31. http://dx.doi.org/10.1093/genetics/141.2.721.
Full textAbstract:
Abstract A molecular-marker linkage map of hexaploid wheat (Triticum aestivum L. em. Thell) provides a framework for integration with teh classical genetic map and a record of the chromosomal rearrangements involved in the evolution of this crop species. We have constructed restriction fragment length polymorphism (RFLP) maps of the A-, B-, and D-genome chromosomes of homoeologous groups 4, 5, and 7 of wheat using 114 F7 lines from a synthetic X cultivated wheat cross and clones from 10 DNA libraries. Chromosomal breakpoints for known ancestral reciprocal translocations involving these chromosomes and for a known pericentric inversion on chromosome 4A were localized by linkage and aneuploid analysis. Known genes mapped include the major vernalization genes Vrn1 and Vrn3 on chromosome arms 5AL and 5DL, the red-coleoptile gene Rc1 on 7AS, and presumptively the leaf-rust (Puccinia recondita f.sp. tritici) resistance gene Lr34 on 7DS and the kernel-hardness gene Ha on 5DS. RFLP markers previously obtained for powdery-mildew (Blumeria graminis f.sp. tritici) resistance genes Pm2 and Pm1 were localized on chromosome arms 5DS and 7AL.
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Donald, Tamzin M., Andreas Houben, Carolyn R. Leach, and Jeremy N. Timmis. "Ribosomal RNA genes specific to the B chromosomes in Brachycome dichromosomatica are not transcribed in leaf tissue." Genome 40, no. 5 (October 1, 1997): 674–81. http://dx.doi.org/10.1139/g97-089.
Full textAbstract:
Ribosomal RNA genes are present near the end of the short arm and, to a lesser extent, near the centromere of the B chromosomes of some populations of Brachycome dichromosomatica. The internal transcribed spacer (ITS2) was amplified by PCR from total leaf DNA using primers within the conserved regions encoding the 5.8S and 25S stable rRNA species. Comparison of PCR amplified ITS2 sequences from several individual plants without B chromosomes with corresponding sequences derived from microdissected B chromosomes revealed two consistent differences between the rDNA of A and B chromosomes. One of these differences produced an SfcI restriction site that was present only in the ITS2 of the B-chromosome rDNA. Amplification by PCR of ITS2 from total genomic DNA from plants with and without B chromosomes showed an additive relationship between the amount of PCR product containing the SfcI site and the number of B chromosomes present. Quantitative analysis indicated that the proportion of total nuclear rDNA present on a single B chromosome varied between 2 and 4% in different A chromosome backgrounds. Similar experiments, with appropriate positive and negative controls, using reverse transcriptase PCR of the equivalent region within the 40S precursor rRNA, suggested that the B-chromosome rDNA was not transcribed. Similarly, PCR of reverse transcribed total RNA from plants containing B chromosomes using primers specific for the B chromosome ITS2 was unable to detect a transcript from the B chromosome. Keywords: B chromosome, ribosomal RNA genes, transcription.
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Carlson, Wayne R. "Locating a site on the maize B chromosome that controls preferential fertilization." Genome 50, no. 6 (June 2007): 578–87. http://dx.doi.org/10.1139/g07-035.
Full textAbstract:
In maize, the B chromosome can undergo nondisjunction at the second pollen mitosis, producing sperm with two B chromosomes and sperm with zero B chromosomes. Preferential fertilization is the ability of the sperm carrying two B chromosomes to transmit more frequently to the embryo of a kernel than the sperm lacking the B chromosome. A translocation involving the B chromosome and chromosome 9, TB-9Sb, has been used to study preferential fertilization. The B-9 chromosome has the same properties of nondisjunction and preferential fertilization as the standard B chromosome. Deletion derivatives of B-9, which lack the centric heterochromatin and possibly some adjacent euchromatin, were tested for their ability to induce preferential fertilization. They were found to lack the capacity for preferential fertilization.
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Dhar, Manoj, Jasmeet Kour, and Sanjana Kaul. "Origin, Behaviour, and Transmission of B Chromosome with Special Reference to Plantago lagopus." Genes 10, no. 2 (February 18, 2019): 152. http://dx.doi.org/10.3390/genes10020152.
Full textAbstract:
B chromosomes have been reported in many eukaryotic organisms. These chromosomes occur in addition to the standard complement of a species. Bs do not pair with any of the A chromosomes and they have generally been considered to be non-essential and genetically inert. However, due to tremendous advancements in the technologies, the molecular composition of B chromosomes has been determined. The sequencing data has revealed that B chromosomes have originated from A chromosomes and they are rich in repetitive elements. In our laboratory, a novel B chromosome was discovered in Plantago lagopus. Using molecular cytogenetic techniques, the B chromosome was found to be composed of ribosomal DNA sequences. However, further characterization of the chromosome using next generation sequencing (NGS) etc. revealed that the B chromosome is a mosaic of sequences derived from A chromosomes, 5S ribosomal DNA (rDNA), 45S rDNA, and various types of repetitive elements. The transmission of B chromosome through the female sex track did not follow the Mendelian principles. The chromosome was found to have drive due to which it was perpetuating in populations. The present paper attempts to summarize the information on nature, transmission, and origin of B chromosomes, particularly the current status of our knowledge in P. lagopus.
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Bernardino, Andrezza C. S., Diogo C. Cabral-de-Mello, Carolina B. Machado, Octavio M. Palacios-Gimenez, Neide Santos, and Vilma Loreto. "B Chromosome Variants of the Grasshopper Xyleus discoideus angulatus Are Potentially Derived from Pericentromeric DNA." Cytogenetic and Genome Research 152, no. 4 (2017): 213–21. http://dx.doi.org/10.1159/000480036.
Full textAbstract:
B chromosomes, extra elements present in the karyotypes of some eukaryote species, have been described in the grasshopper Xyleus discoideus angulatus. Although some studies have proposed an autosomal origin of the B chromosome in X. d. angulatus, little is known about its repetitive DNA composition and evolutionary dynamics. The aim of the present work was to shed light on the B chromosome evolution in X. d. angulatus by cytogenetic analysis of 27 populations from Pernambuco and Ceará states (Brazil). The frequency of B chromosomes in the different populations was determined, and chromosome measurements and fluorescence in situ hybridization (FISH) with C0t-DNA and telomeric and B chromosome sequences were performed in cells from B-carrying individuals. The results revealed variations in B chromosome prevalence among the populations and showed that some B chromosomes were smaller in certain populations. FISH produced similar patterns for the C0t-DNA probe in all hybridized individuals, whereas telomeric and B chromosome probes, obtained by microdissection, exhibited variations in their distribution. These results indicate the presence of 3 morphotypes of B chromosomes in X. d. angulatus, with variation in repetitive DNA composition during their evolution. In this species, B chromosomes have an intraspecific origin and probably arose from the pericentromeric region of A chromosomes.
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Quiros, C. F., F. Grellet, J. Sadowski, T. Suzuki, G. Li, and T. Wroblewski. "Arabidopsis and Brassica Comparative Genomics: Sequence, Structure and Gene Content in the ABI1-Rps2-Ck1 Chromosomal Segment and Related Regions." Genetics 157, no. 3 (March 1, 2001): 1321–30. http://dx.doi.org/10.1093/genetics/157.3.1321.
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Abstract The region corresponding to the ABI1-Rps2-Ck1 segment on chromosome 4 of Arabidopsis thaliana was sequenced in Brassica oleracea. Similar to A. thaliana, the B. oleracea homolog BoRps2 is present in single copy. The B. oleracea orthologous segment was located on chromosome 4 and can be distinguished by the presence of an N-myristoyl transferase coding gene (N-myr) between the Rps2 and Ck1 (BoCk1a) genes. The N-myr homologs in Arabidopsis are on chromosomes 2 and 5. Additional homologs for Ck1 are located on these two chromosomes. A second Ck1 homolog found on B. oleracea (BoCk1b) chromosome 7 served to define another orthologous segment located in Arabidopsis chromosome 1. The two segments displayed identical gene content and order in both species, namely BoCK1b, a gene encoding a hypothetical protein (BohypothA) and transcription factor eiF4A. High levels of sequence identity were observed for the coding sequences of all genes examined. Although in general larger spacers were found in Brassica than in A. thaliana, this was not always the case. Promoters were poorly conserved, except for several sequence stretches of a few nucleotides. Comparative sequencing revealed microsyntenic changes resulting from chromosomal structural rearrangements, which are often undetectable by genetic mapping.
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Olin-Fatih, Majlis, and W. K. Heneen. "C-banded karyotypes of Brassica campestris, B. oleracea, and B. napus." Genome 35, no. 4 (August 1, 1992): 583–89. http://dx.doi.org/10.1139/g92-087.
Full textAbstract:
The chromosome complements of three Brassica species, namely B. campestris (2n = 20), B. oleracea (2n = 18), and B. napus (2n = 38), were studied using the air-dry method and C-banding. Karyotypes and ideograms of late prophase chromosomes were constructed, since contracted metaphase chromosomes were generally not suitable for this purpose. The three species generally had a similar banding pattern, manifested in the presence of a centromeric C-band in all chromosomes and heterochromatic knobs at the telomeric end of some chromosomes. The centromeric C-bands were more pronounced in B. campestris than in B. oleracea. Depending on the centromeric position, the chromosomes were grouped into median, submedian, subterminal, and terminal types. All chromosome pairs were morphologically distinguishable. Only one nucleolar chromosome pair, with heterochromatic satellites, was observed in each species. When compared, it was possible to distinguish chromosomes of both B. campestris and B. oleracea type in B. napus, but conclusive evidence as to the origin of all chromosome pairs in B. napus was not at hand.Key words: Brassica, chromosomes, late prophase, C-bands, knob structures, karyotypes, idiograms.
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Fujii, Tsuguru, Seigo Kuwazaki, Kimiko Yamamoto, Hiroaki Abe, Akio Ohnuma, Susumu Katsuma, Kazuei Mita, and Toru Shimada. "Identification and molecular characterization of a sex chromosome rearrangement causing a soft and pliable (spli) larval body phenotype in the silkworm, Bombyx mori." Genome 53, no. 1 (January 2010): 45–54. http://dx.doi.org/10.1139/g09-083.
Full textAbstract:
We carried out genetic and cytogenetic analyses of X-ray-induced deleterious Z chromosomes that result in a soft and pliable (spli) phenotype in the silkworm, Bombyx mori . In a B. mori strain with a spli phenotype, we found the Z chromosome broken between the sch (1–21.5) and od (1–49.6) loci. We also found a chromosomal fragment bearing a fifth-chromosome locus for egg and eye pigmentation fused to a Z chromosome fragment. By means of fluorescence in situ hybridization using bacterial artificial chromosome clones as probes, we confirmed that the fused chromosome is composed of a fragment of chromosome 5 and a fragment of the Z chromosome. Moreover, a predicted gene, GA002017, the Bombyx ortholog of the Drosophila gene acj6 (Bmacj6), was completely deleted by the Z chromosome breakage event. The relationship between Bmacj6 and the spli phenotype is discussed.
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Jang, Tae-Soo, John Parker, and Hanna Weiss-Schneeweiss. "Euchromatic Supernumerary Chromosomal Segments—Remnants of Ongoing Karyotype Restructuring in the Prospero autumnale Complex?" Genes 9, no. 10 (September 27, 2018): 468. http://dx.doi.org/10.3390/genes9100468.
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Supernumerary chromosomal segments (SCSs) represent additional chromosomal material that, unlike B chromosomes, is attached to the standard chromosome complement. The Prospero autumnale complex (Hyacinthaceae) is polymorphic for euchromatic large terminal SCSs located on the short arm of chromosome 1 in diploid cytotypes AA and B7B7, and tetraploid AAB7B7 and B6B6B7B7, in addition to on the short arm of chromosome 4 in polyploid B7B7B7B7 and B7B7B7B7B7B7 cytotypes. The genomic composition and evolutionary relationships among these SCSs have been assessed using fluorescence in situ hybridisation (FISH) with 5S and 35S ribosomal DNAs (rDNAs), satellite DNA PaB6, and a vertebrate-type telomeric repeat TTAGGG. Neither of the rDNA repeats were detected in SCSs, but most contained PaB6 and telomeric repeats, although these never spanned whole SCSs. Genomic in situ hybridisation (GISH) using A, B6, and B7 diploid genomic parental DNAs as probes revealed the consistently higher genomic affinity of SCSs in diploid hybrid B6B7 and allopolyploids AAB7B7 and B6B6B7B7 to genomic DNA of the B7 diploid cytotype. GISH results suggest a possible early origin of SCSs, especially that on chromosome 1, as by-products of the extensive genome restructuring within a putative ancestral P. autumnale B7 genome, predating the complex diversification at the diploid level and perhaps linked to B-chromosome evolution.
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Tu, Y. Q., J. Sun, X. H. Ge, and Z. Y. Li. "Production and genetic analysis of partial hybrids from intertribal sexual crosses between Brassica napus and Isatis indigotica and progenies." Genome 53, no. 2 (February 2010): 146–56. http://dx.doi.org/10.1139/g09-093.
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With the dye and medicinal plant Isatis indigotica (2n = 14) as pollen parent, intertribal sexual hybrids with Brassica napus (2n = 38, AACC) were obtained and characterized. Among a lot of F1 plants produced, only five hybrids (H1–H5) were distinguished morphologically from female B. napus parents by showing low fertility and some characters of I. indigotica, and also by having different chromosome numbers. H1–H4 had similar but variable chromosome numbers in their somatic and meiotic cells (2n = 25–30), and H5 had 2n = 19, the same number as the haploid of B. napus. GISH analysis of the cells from H1 and H5 detected one I. indigotica chromosome and one or two chromosome terminal fragments. New B. napus types with phenotypic and genomic alterations were produced by H1 after pollination by B. napus and selfing for several generations, and by H5 after selfing. A progeny plant (2n = 20) was derived from H1 after pollination by I. indigotica twice and had a phenotype similar to a certain type of B. rapa, showing that hybrid H1 likely retained all chromosomes of the A genome and lost some of the C genome in parental B. napus. The reasons for the formation of the partial hybrids with unexpected chromosomal complements and for the chromosome elimination are discussed.