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1
Yeadon, P. Jane, J. Paul Rasmussen, and David E. A. Catcheside. "Recombination Events in Neurospora crassa May Cross a Translocation Breakpoint by a Template-Switching Mechanism." Genetics 159, no. 2 (October 1, 2001): 571–79. http://dx.doi.org/10.1093/genetics/159.2.571.
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Abstract To assist investigation of the effect of sequence heterology on recombination in Neurospora crassa, we inserted the Herpes simplex thymidine kinase gene (TK) as an unselected marker on linkage group I, giving a gene order of Cen–his-3–TK–cog–lpl. We show here that in crosses heterozygous for TK, conversion of a his-3 allele on one homolog is accompanied by transfer of the heterologous sequence between cog and his-3 from the other homolog, indicating that recombination is initiated centromere-distal of TK. We have identified a 10-nucleotide motif in the cog region that, although unlikely to be sufficient for hotspot activity, is required for high-frequency recombination and, because conversion of silent sequence markers declines on either side, may be the recombination initiation site. Additionally, we have mapped conversion tracts in His+ progeny of a translocation heterozygote, in which the translocation breakpoint separates cog from the 5′ end of his-3. We present molecular evidence of recombination on both sides of the breakpoint. Because recombination is initiated close to cog and the event must therefore cross the translocation breakpoint, we suggest that template switching occurs in some recombination events, with repair synthesis alternating between use of the homolog and the initiating chromatid as template.
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Perkins, David D., Robert L. Metzenberg, Namboori B. Raju, Eric U. Selker, and Edward G. Barry. "REVERSAL OF A NEUROSPORA TRANSLOCATION BY CROSSING OVER INVOLVING DISPLACED rDNA, AND METHYLATION OF THE rDNA SEGMENTS THAT RESULT FROM RECOMBINATION." Genetics 114, no. 3 (November 1, 1986): 791–817. http://dx.doi.org/10.1093/genetics/114.3.791.
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ABSTRACT In translocation OY321 of Neurospora crassa, the nucleolus organizer is divided into two segments, a proximal portion located interstitially in one interchange chromosome, and a distal portion now located terminally on another chromosome, linkage group I. In crosses of Translocation x Translocation, exceptional progeny are recovered nonselectively in which the chromosome sequence has apparently reverted to Normal. Genetic, cytological, and molecular evidence indicates that reversion is the result of meiotic crossing over between homologous displaced rDNA repeats. Marker linkages are wild type in these exceptional progeny. They differ from wild type, however, in retaining an interstitial block of rRNA genes which can be demonstrated cytologically by the presence of a second, small interstitial nucleolus and genetically by linkage of an rDNA restriction site polymorphism to the mating-type locus in linkage group I. The interstitial rDNA is more highly methylated than the terminal rDNA. The mechanism by which methylation enzymes distinguish between interstitial rDNA and terminal rDNA is unknown. Some hypotheses are considered.
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Lu, Benjamin C. "Karyotyping ofNeurospora crassausing synaptonemal complex spreads of translocation quadrivalents." Genome 49, no. 6 (June 1, 2006): 612–18. http://dx.doi.org/10.1139/g06-008.
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The purposes of the present research are (i) to establish the karyotype of Neursopora crassa using visualization of kinetochores in the synaptonemal complex (SC) spreads, (ii) to assign each chromosome to a linkage group, and (iii) to examine chromosome pairing and recombination nodules in quadrivalents. Two strains containing reciprocal translocations were used: T(I;II)4637, which involves linkage groups I and II, and alcoy, which contains 3 independent translocations involving I and II, IV and V, and III and VI. Visualization of kinetochores in the spreads requires the use of freshly prepared fixatives. Kinetochore locations and arm ratios were documented in all 7 N. crassa chromosomes. This new information, based on kinetochore position, arm ratios, chromosome length, and quadrivalent analyses, enabled unequivocal confirmation of chromosome assignments to genetic linkage groups. Chromosome pairing in a translocation quadrivalent starts at the 4 terminal regions, and proceeds right up to the translocation break point. Recombination nodules are found in all 4 arms of quadrivalents. The ability to identify a specific chromosome to a genetic linkage group together with the ability to visualize recombination nodules and their locations will allow future cytological analysis of recombination events.Key words: Neurospora, synaptonemal complex, translocation, karyotype, kinetochore, linkage groups, recombination nodules.
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Lukaszewski, Adam J. "Genetic mapping in the 1R.1D wheat–rye translocated chromosomes." Genome 37, no. 6 (December 1, 1994): 945–49. http://dx.doi.org/10.1139/g94-134.
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Translocation chromosomes 1R.1D5+10−1 and 1R.1D5+10−2 were produced to improve bread-making quality in triticale and to manipulate the dosage of the Glu-D1 gene in wheat. They involve transfers of segments of the long arm of chromosome 1D of bread wheat to the long arm of rye chromosome 1R. The translocated long arms of the chromosomes were mapped genetically in wheat and triticale using polymorphism for C-banding patterns, allelic variation of the Glu-D1 gene, and a telocentric chromosome 1RL. The total frequency and the general distribution of recombination in the translocated arms was similar to that in normal long arms of group-1 chromosomes in wheat, rye, and triticale, except that the distal rye segments of the translocations showed a 15- to 20-fold increase in recombination frequency compared with normal 1R. Despite major differences in the physical structure of the translocated arms, both appeared very similar genetically, suggesting that genetic mapping is a poor indicator of the physical structure of translocations. Genetic length of the 1DL segment in chromosome 1R.1D5+10−1 was 31 cM, making the chromosome unsuitable for Glu-D1 dosage manipulation in wheat. The potential of chromosome 1R.1D5+10−2 for wheat breeding needs further testing. However, both chromosomes behave normally in hexaploid triticale.Key words: translocation, linkage, bread-making quality, wheat, triticale.
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Franz, G., E. Gencheva, and Ph Kerremans. "Improved stability of genetic sex-separation strains for the Mediterranean fruit fly, Ceratitis capitata." Genome 37, no. 1 (February 1, 1994): 72–82. http://dx.doi.org/10.1139/g94-009.
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In the existing genetic sexing strains for the medfly, Ceratitis capitata, male recombination leads to breakdown of the sexing mechanism under mass rearing conditions. The rate of breakdown depends on the recombination frequency and on the fitness of the recombinants. We have tested two different sexing genes, white pupa and a temperature sensitive lethal, in combination with the translocation T(Y;5)30C. Both sexing strains broke down, although at very different rates. In the case of the white pupa strain, 3.5% recombinants were observed after rearing the strain for 15 generations. The second strain, utilizing white pupa and the temperature sensitive lethal as selectable markers, already reached a comparable level after six generations and was broken down completely in the ninth generation. In these strains the frequency of recombination is high because the breakpoint of T(Y;5)30C and the sexing gene(s) are far apart. To remedy the situation, we have isolated four new translocations with breakpoints located closer to the sexing genes. Mass rearing was simulated for several generations with strains based on these translocations and no breakdown was observed under the conditions used.Key words: medfly, sterile insect technique, genetic sexing, recombination.
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Sybenga, J., H. M. Verhaar, and D. G. A. Botje. "Trisomy greatly enhances interstitial crossing over in a translocation heterozygote of Secale." Genome 55, no. 1 (January 2012): 15–25. http://dx.doi.org/10.1139/g11-071.
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Chromosomal rearrangements, including reciprocal translocations, may prevent recombinational transfer of genes from a donor genotype to a recipient, especially when the gene is located in an interstitial segment. The effect of trisomy of chromosome arm 1RS on recombination was studied in translocation heterozygote T248W of rye ( Secale cereale ), involving chromosome arms 1RS and 6RS. (Pro)metaphase I configuration frequencies were analyzed. Crossing over, estimated as chiasma parameters, in five genetically different euploid heterozygotes was compared with those of 10 different single arm trisomics. The addition of 1RS greatly altered the crossing over pattern around the translocation break point, with a special increase in the interstitial segment of 6RS and adjoining regions, normally hardly accessible to recombination. Furthermore, there was considerable variation between plants of closely related genotypes. Heterogeneity widens the distribution of crossing overs, including segments normally not accessible to recombination, but decreases average recombination in other segments. The extra chromosome and abnormal segregants are eliminated by using the trisomic as the pollen parent.
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Hiraoka, Mina, Kei-ichi Watanabe, Keiko Umezu, and Hisaji Maki. "Spontaneous Loss of Heterozygosity in Diploid Saccharomyces cerevisiae Cells." Genetics 156, no. 4 (December 1, 2000): 1531–48. http://dx.doi.org/10.1093/genetics/156.4.1531.
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Abstract To obtain a broad perspective of the events leading to spontaneous loss of heterozygosity (LOH), we have characterized the genetic alterations that functionally inactivated the URA3 marker hemizygously or heterozygously situated either on chromosome III or chromosome V in diploid Saccharomyces cerevisiae cells. Analysis of chromosome structure in a large number of LOH clones by pulsed-field gel electrophoresis and PCR showed that chromosome loss, allelic recombination, and chromosome aberration were the major classes of genetic alterations leading to LOH. The frequencies of chromosome loss and chromosome aberration were significantly affected when the marker was located in different chromosomes, suggesting that chromosome-specific elements may affect the processes that led to these alterations. Aberrant-sized chromosomes were detected readily in ∼8% of LOH events when the URA3 marker was placed in chromosome III. Molecular mechanisms underlying the chromosome aberrations were further investigated by studying the fate of two other genetic markers on chromosome III. Chromosome aberration caused by intrachromosomal rearrangements was predominantly due to a deletion between the MAT and HMR loci that occurred at a frequency of 3.1 × 10-6. Another type of chromosome aberration, which occurred at a frequency slightly higher than that of the intrachromosomal deletion, appeared to be caused by interchromosomal rearrangement, including unequal crossing over between homologous chromatids and translocation with another chromosome.
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Hall, K. J., J. S. Parker, and T. H. N. Ellis. "The relationship between genetic and cytogenetic maps of pea. I. Standard and translocation karyotypes." Genome 40, no. 5 (October 1, 1997): 744–54. http://dx.doi.org/10.1139/g97-797.
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A detailed cytogenetical study of inbred lines of pea and their F1 hybrids has been undertaken to study the relationship between the cytogenetic map and the molecular linkage map. The mitotic karyotypes of a standard pea line, JI15, a translocation line, JI61, and line JI281, a line used in the production of a mapping population, are given. A chromosome rearrangement detected by cytogenetic analysis of mitotic chromosomes has been further defined by synaptonemal complex (SC) analysis and the study of metaphase I chromosome behaviour. This meiotic analysis has allowed a comparison of SC physical lengths, observed chiasma frequencies, and recombination frequencies, as estimated from the genetic map, as a means of comparing physical and genetic distances.Key words: Pisum, linkage map, cytogenetics, chromosome rearrangement, synaptonemal complex.
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Brubaker, C. L., A. H. Paterson, and J. F. Wendel. "Comparative genetic mapping of allotetraploid cotton and its diploid progenitors." Genome 42, no. 2 (April 1, 1999): 184–203. http://dx.doi.org/10.1139/g98-118.
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Allotetraploid cotton species (Gossypium) belong to a 1-2 million year old lineage that reunited diploid genomes that diverged from each other 5-10 million years ago. To characterize genome evolution in the diploids and allotetraploids, comparative RFLP mapping was used to construct genetic maps for the allotetraploids (AD genome; n = 26) and diploids (A and D genomes; n = 13). Comparisons among the 13 suites of homoeologous linkage groups permitted comparisons of synteny and gene order. Two reciprocal translocations were confirmed involving four allotetraploid At genome chromosomes, as was a translocation between the two extant A genome diploids. Nineteen locus order differences were detected among the two diploid and two allotetraploid genomes. Conservation of colinear linkage groups among the four genomes indicates that allopolyploidy in Gossypium was not accompanied by extensive chromosomal rearrangement. Many inversions include duplicated loci, suggesting that the processes that gave rise to inversions are not fully conservative. Allotetraploid At and Dt genomes and the A and D diploid genomes are recombinationally equivalent despite a nearly two-fold difference in physical size. Polyploidization in Gossypium is associated with enhanced recombination, as genetic lengths for allotetraploid genomes are over 50% greater than those of their diploid counterparts.Key words: restriction fragment length polymorphism (RFLP), Gossypium, evolution, polyploidy.
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Desai, Aparna, Peng W. Chee, Junkang Rong, O. Lloyd May, and Andrew H. Paterson. "Chromosome structural changes in diploid and tetraploid A genomes of Gossypium." Genome 49, no. 4 (April 1, 2006): 336–45. http://dx.doi.org/10.1139/g05-116.
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The genus Gossypium, which comprises a divergent group of diploid species and several recently formed allotetraploids, offers an excellent opportunity to study polyploid genome evolution. In this study, chromosome structural variation among the A, At, and D genomes of Gossypium was evaluated by comparative genetic linkage mapping. We constructed a fully resolved RFLP linkage map for the diploid A genome consisting of 275 loci using an F2 interspecific Gossypium arboreum × Gossypium herbaceum family. The 13 chromosomes of the A genome are represented by 12 large linkage groups in our map, reflecting an expected interchromosomal translocation between G. arboreum and G. herbaceum. The A-genome chromosomes are largely collinear with the D genomes, save for a few small inversions. Although the 2 diploid mapping parents represent the closest living relatives of the allotetraploid At-genome progenitor, 2 translocations and 7 inversions were observed between the A and At genomes. The recombination rates are similar between the 2 diploid genomes; however, the At genome shows a 93% increase in recombination relative to its diploid progenitors. Elevated recombination in the Dt genome was reported previously. These data on the At genome thus indicate that elevated recombination was a general property of allotetraploidy in cotton.Key words: comparative mapping, polyploidy, genome evolution, inversions, translocations, RFLP.
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Cladera, Jorge L., and M. Alejandra Delprat. "Genetic and cytological mapping of a "Y–2" translocation in the Mediterranean fruit fly Ceratitis capitata." Genome 38, no. 6 (December 1, 1995): 1091–97. http://dx.doi.org/10.1139/g95-145.
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In this paper we analyze genetically and cytologically a Y – chromosome 2 translocation with several markers, some of which are potentially useful for large scale sex separation. The breakpoint of this Y–2 translocation is located at region 6B on the trichogene polytene chromosome map. It was found that, in strains carrying this TY–2, only 40% of the fertilized eggs survived to the adult stage, 26% of them dying as embryos, 27% as larvae, and 7% as pupae. Early lethality is explained by the nonviability of adjacent-1 products of meiosis containing a deletion of section 1A–6B. The reciprocal segregation products, carrying this chromosome segment in triplicate, survive until late stages. By analyzing the phenotype of these individuals we conclude that all markers used in this study are located outside the triplicated region and that the male determining factor is not included in the piece of the Y chromosome translocated to chromosome 2. The male recombination frequencies of several genes located on chromosome 2 relative to the breakpoint of translocation T5038 have also been studied here.Key words: genetic sexing strain, Medfly polytene chromosome, adjacent-1 product, translocation breakpoint mapping.
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Lukaszewski, A. J., K. Rybka, V. Korzun, S. V. Malyshev, B. Lapinski, and R. Whitkus. "Genetic and physical mapping of homoeologous recombination points involving wheat chromosome 2B and rye chromosome 2R." Genome 47, no. 1 (January 1, 2004): 36–45. http://dx.doi.org/10.1139/g03-089.
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Wide hybrids have been used in generating genetic maps of many plant species. In this study, genetic and physical mapping was performed on ph1b-induced recombinants of rye chromosome 2R in wheat (Triticum aestivum L.). All recombinants were single breakpoint translocations. Recombination 2RS–2BS was absent from the terminal and the pericentric regions and was distributed randomly along an intercalary segment covering approximately 65% of the arm's length. Such a distribution probably resulted from structural differences at the telomeres of 2RS and wheat 2BS arm that disrupted telomeric initiation of pairing. Recombination 2RL–2BL was confined to the terminal 25% of the arm's length. A genetic map of homoeologous recombination 2R–2B was generated using relative recombination frequencies and aligned with maps of chromosomes 2B and 2R based on homologous recombination. The alignment of the short arms showed a shift of homoeologous recombination toward the centromere. On the long arms, the distribution of homoeologous recombination was the same as that of homologous recombination in the distal halves of the maps, but the absence of multiple crossovers in homoeologous recombination eliminated the proximal half of the map. The results confirm that homoeologous recombination in wheat is based on single exchanges per arm, indicate that the distribution of these single homoeologous exchanges is similar to the distribution of the first (distal) crossovers in homologues, and suggest that successive crossovers in an arm generate specific portions of genetic maps. A difference in the distribution of recombination between the short and long arms indicates that the distal crossover localization in wheat is not dictated by a restricted distribution of DNA sequences capable of recombination but by the pattern of pairing initiation, and that can be affected by structural differences. Restriction of homoeologous recombination to single crossovers in the distal part of the genetic map complicates chromosome engineering efforts targeting genes in the proximal map regions.Key words: homoeologous recombination, genetic mapping, RFLP, RAPD, wheat, rye.
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Newth, David, and David G. Green. "The Role of Translocation and Selection in the Emergence of Genetic Clusters and Modules." Artificial Life 13, no. 3 (July 2007): 249–58. http://dx.doi.org/10.1162/artl.2007.13.3.249.
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Biomolecular studies point increasingly to the importance of modularity in the organization of the genome. Processes such as the maintenance of metabolism are controlled by suites of genes that act as distinct, self-contained units, or modules. One effect is to promote stability of inherited characters. Despite the obvious importance of genetic modules, the mechanisms by which they form and persist are not understood. One clue is that functionally related genes tend to cluster together. Here we show that genetic translocation, recombination, and natural selection play a central role in this process. We distill the question of emerging genetic modularity into three simulation experiments that show: (1) a tendency, under natural selection, for essential genes to co-locate on the same chromosome and to settle in fixed loci; (2) that genes associated with a particular function tend to form functional clusters; and (3) that genes within a functional cluster tend to become arranged in transcription order. The results also imply that high proportions of junk DNA are essential to the process.
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Wolff, Daynna J., and Stuart Schwartz. "The effect of Robertsonian translocation on recombination on chromosome 21." Human Molecular Genetics 2, no. 6 (1993): 693–99. http://dx.doi.org/10.1093/hmg/2.6.693.
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Zwierzykowski, Z., A. J. Lukaszewski, B. Naganowska, and A. Lesniewska. "The pattern of homoeologous recombination in triploid hybrids of Lolium multiflorum with Festuca pratensis." Genome 42, no. 4 (August 1, 1999): 720–26. http://dx.doi.org/10.1139/g98-169.
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Homoeologous chromosomes of Lolium-Festuca hybrids are capable of frequent meiotic pairing and recombination. The frequency and distribution of recombination was studied by genomic in situ hybridization in backcross progenies of reciprocal triploid hybrids of Lolium multiflorum with Festuca pratensis. Significant differences in the male transmission of the parental and translocated chromosomes were observed depending on the cytoplasm of the F1 hybrids and the ploidy level of the female test cross partner. The frequency of intergeneric translocations in the progeny indicated that, on average, there must have been at least 4.5 homoeologous arms paired in the F1 hybrids; the actual frequency might have been higher because of pre- or post-zygotic selection against the F. pratensis chromatin, which probably eliminated certain gametes with Festuca-Lolium translocations. Both parental species are known for localized distal chiasmata, but the intergeneric translocation breakpoints were distributed along the entire lengths of the chromosome arms. The change in the distribution of homoeologous recombination might have been related to different pairing initiation of homologues and homoeologues. It probably resulted from allocation of additional chiasmata to chromosome arms and produced a net increase in recombination.Key words: homoeologous exchanges, Lolium-Festuca, translocations, recombination.
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Kerremans, Ph, E. Gencheva, and G. Franz. "Genetic and cytogenetic analysis of Y-autosome translocations in the Mediterranean fruit fly, Ceratitis capitata." Genome 35, no. 2 (April 1, 1992): 264–72. http://dx.doi.org/10.1139/g92-041.
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Radiation-induced translocations in the Mediterranean fruit fly, Ceratitis capitata, linking the Y chromosome to either autosome 3 or 4 produced pseudolinkage between sex and the mutations dark pupa (dp) and apricot eye (ap), respectively. The genetic behaviour of six new strains is described and the structural basis of five of them is determined through analysis of polytene and mitotic chromosomes. Five strains exhibited low levels of recombination; however, one strain produced a larger number than expected of aberrant, wild-type females. We provide evidence that this is the consequence of the survival of adjacent-1 segregation products until adulthood.Key words: medfly, mass rearing, genetic sexing, recombination, segregation.
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Künzel, G., K. I. Gecheff, and I. Schubert. "Different chromosomal distribution patterns of radiation-induced interchange breakpoints in barley: First post-treatment mitosis versus viable offspring." Genome 44, no. 1 (February 1, 2001): 128–32. http://dx.doi.org/10.1139/g00-104.
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Translocation breakpoints (TBs) induced by ionizing radiation are nonrandomly distributed along barley chromosomes. When first post-treatment mitoses were evaluated, centromeres and the heterochromatin-containing proximal segments tended to be more than randomly involved, and terminal segments to be less than randomly involved in translocations. Contrary to this, small chromosomal regions in median and distal arm positions, characterized by high recombination rates and high gene density, were identified as preferred sites for the origination of viable translocations, probably due to deviations in chromatin organization. Apparently, the position of a TB has an influence on the rate of viability versus elimination of the carrier cells. Surprisingly, TBs within centromeres and heterochromatin-containing segments seem to be more harmful for survival than those induced in gene-rich regions.Key words: Hordeum vulgare, radiation-induced chromosome breaks, translocation lines, breakpoint distribution.
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Sharpe, A. G., I. A. P. Parkin, D. J. Keith, and D. J. Lydiate. "Frequent nonreciprocal translocations in the amphidiploid genome of oilseed rape (Brassica napus)." Genome 38, no. 6 (December 1, 1995): 1112–21. http://dx.doi.org/10.1139/g95-148.
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A RFLP map of Brassica napus, consisting of 277 loci arranged in 19 linkage groups, was produced from genetic segregation in a combined population of 174 doubled-haploid microspore-derived lines. The integration of this map with a B. napus map derived from a resynthesized B. napus × oilseed rape cross allowed the 10 linkage groups of the B. napus A genome and the 9 linkage groups of the C genome to be identified. Collinear patterns of marker loci on different linkage groups suggested potential partial homoeologues. RFLP patterns consistent with aberrant chromosomes were observed in 9 of the 174 doubled-haploid lines. At least 4 of these lines carried nonreciprocal, homoeologous translocations. These translocations were probably the result of homoeologous recombination in the amphidiploid genome of oilseed rape, suggesting that domesticated B. napus is unable to control chromosome pairing completely. Evidence for genome homogenization in oilseed rape is presented and its implications on genetic mapping in amphidiploid species is discussed. The level of polymorphism in the A genome was higher than that in the C genome and this might be a general property of oilseed rape crosses.Key words: restriction fragment length polymorphism, genetic linkage map, homoeologous recombination, microspore culture, doubled haploid.
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Fenton, James A. L., Guy Pratt, Dominic G. Rothwell, Andy C. Rawstron, and Gareth J. Morgan. "Translocation t(11;14) in multiple myeloma: Analysis of translocation breakpoints on der(11) and der(14) chromosomes suggests complex molecular mechanisms of recombination." Genes, Chromosomes and Cancer 39, no. 2 (2003): 151–55. http://dx.doi.org/10.1002/gcc.10304.
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Goicoechea, P. G., A. Roca, T. Naranjo, and R. Giraldez. "Interstitial chiasmata and centromere orientation in heterozygotes for a translocation in rye." Genome 29, no. 4 (August 1, 1987): 647–57. http://dx.doi.org/10.1139/g87-109.
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The meiotic behaviour of plants heterozygous for translocation T242W of rye (involving 2RL and 6RL) and an interstitial C-band in 2RL has been analyzed. Chain and frying pan quadrivalents predominate. The following results have further been obtained: (i) double chiasmata occur in the interstitial segment carrying the C-band; (ii) from the frequency of being bound at metaphase I and the frequency of recombinant chromosomes at anaphase I, estimates of chiasma frequencies (and chiasma interference) in interstitial segments have been derived; (iii) estimates of the recombination fraction between the interstitial C-band and the translocation breakpoint have been obtained from offspring analysis; (iv) there is a difference in the frequency of alternate orientation between configurations with and without interstitial chiasmata (adjacent-2 has not been observed and a small but significant excess of alternate vs. adjacent-1 coorientation appears). Without intersitial chiasmata, alternate orientation predominates. The possible reasons for these differences are discussed. Key words: Secale cereale, translocations, chiasma frequency, centromere orientation.
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Szankasi, Philippe, Christof Gysler, Ulrich Zehntner, Urs Leupold, Jürg Kohli, and Peter Munz. "Mitotic recombination between dispersed but related rRNA genes of Schizosaccharomyces pombe generates a reciprocal translocation." Molecular and General Genetics MGG 202, no. 3 (March 1986): 394–402. http://dx.doi.org/10.1007/bf00333268.
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Xue, Chaoyou, James M. Daley, Xiaoyu Xue, Justin Steinfeld, Youngho Kwon, Patrick Sung, and Eric C. Greene. "Single-molecule visualization of human BLM helicase as it acts upon double- and single-stranded DNA substrates." Nucleic Acids Research 47, no. 21 (September 23, 2019): 11225–37. http://dx.doi.org/10.1093/nar/gkz810.
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Abstract Bloom helicase (BLM) and its orthologs are essential for the maintenance of genome integrity. BLM defects represent the underlying cause of Bloom Syndrome, a rare genetic disorder that is marked by strong cancer predisposition. BLM deficient cells accumulate extensive chromosomal aberrations stemming from dysfunctions in homologous recombination (HR). BLM participates in several HR stages and helps dismantle potentially harmful HR intermediates. However, much remains to be learned about the molecular mechanisms of these BLM-mediated regulatory effects. Here, we use DNA curtains to directly visualize the activity of BLM helicase on single molecules of DNA. Our data show that BLM is a robust helicase capable of rapidly (∼70–80 base pairs per second) unwinding extensive tracts (∼8–10 kilobases) of double-stranded DNA (dsDNA). Importantly, we find no evidence for BLM activity on single-stranded DNA (ssDNA) that is bound by replication protein A (RPA). Likewise, our results show that BLM can neither associate with nor translocate on ssDNA that is bound by the recombinase protein RAD51. Moreover, our data reveal that the presence of RAD51 also blocks BLM translocation on dsDNA substrates. We discuss our findings within the context of potential regulator roles for BLM helicase during DNA replication and repair.
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Ji, Yuanfu, Wayne A. Raska, Marcos De Donato, M. Nurul Islam-Faridi, H. James Price, and David M. Stelly. "Identification and distinction among segmental duplication-deficiencies by fluorescence in situ hybridization (FISH)-adorned multivalent analysis." Genome 42, no. 4 (August 1, 1999): 763–71. http://dx.doi.org/10.1139/g99-012.
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Most simple reciprocal translocation homozygotes and heterozygotes are euploid, and normal in genotype. However, translocation heterozygotes form six types of numerically balanced meiotic products. The cross of a translocation heterozygote with a normal individual can yield normal progeny, translocation heterozygotes, or any of four segmentally aneuploid duplication-deficient types (dp-dfs). Using metaphase I configuration analysis, most dp-dfs can be distinguished easily from normal and heterozygous translocations. However, identification of the four dp-df types is often impossible unless there is an appreciable karyotypic difference in arm size, relative breakpoint position, or a diagnostic cytological marker. Here we demonstrated the utility and facility of dp-df identification by means of meiotic fluorescence in situ hybridization (FISH) to adorn one chromosome arm with a molecular marker. The rationale is presented diagrammatically, and exemplified by identifying both adjacent-1 and adjacent-2 dp-dfs in Gossypium hirsutum. Polymorphism is not required among marker loci, so analysis of dp-dfs can proceed without requirement of sexual hybridization or sophisticated high-polymorphism marker systems. Besides facilitating the identification of dp-dfs, such an analysis can provide facile means to assign marker loci to chromosomes, arms, and segments. Integrative mapping of chromosomal, physical, and recombination maps will thus be facilitated. An ability to readily distinguish adjacent-1 and adjacent-2 types of dp-dfs should also enhance strategic derivation of other aneuploids, e.g., dp-df related monosomes and trisomes.Key words: Gossypium, cotton, duplication-deficiency, fluorescence in situ hybridization, repetitive DNA.
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Buchholz, Frank, Yosef Refaeli, Andreas Trumpp, and J. Michael Bishop. "Inducible chromosomal translocation of AML1 and ETO genes through Cre/loxP‐mediated recombination in the mouse." EMBO reports 1, no. 2 (August 2000): 133–39. http://dx.doi.org/10.1093/embo-reports/kvd027.
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Lu, Ming, Ian Dubé, Susana Raimondi, Andrew Carroll, Ying Zhao, Mark Minden, and Peter Sutherland. "Molecular characterization of the t(10;14) translocation breakpoints in T-cell acute lymphoblastic leukemia: Further evidence for illegitimate physiological recombination." Genes, Chromosomes and Cancer 2, no. 3 (September 1990): 217–22. http://dx.doi.org/10.1002/gcc.2870020309.
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Danzmann, Roy G., Margaret Cairney, William S. Davidson, Moira M. Ferguson, Karim Gharbi, Rene Guyomard, Lars-Erik Holm, et al. "A comparative analysis of the rainbow trout genome with 2 other species of fish (Arctic charr and Atlantic salmon) within the tetraploid derivative Salmonidae family (subfamily: Salmoninae)." Genome 48, no. 6 (December 1, 2005): 1037–51. http://dx.doi.org/10.1139/g05-067.
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We updated the genetic map of rainbow trout (Oncorhynchus mykiss) for 2 outcrossed mapping panels, and used this map to assess the putative chromosome structure and recombination rate differences among linkage groups. We then used the rainbow trout sex-specific maps to make comparisons with 2 other ancestrally polyploid species of salmonid fishes, Arctic charr (Salvelinus alpinus) and Atlantic salmon (Salmo salar) to identify homeologous chromosome affinities within each species and ascertain homologous chromosome relationships among the species. Salmonid fishes exhibit a wide range of sex-specific differences in recombination rate, with some species having the largest differences for any vertebrate species studied to date. Our current estimate of female:male recombination rates in rainbow trout is 4.31:1. Chromosome structure and (or) size is associated with recombination rate differences between the sexes in rainbow trout. Linkage groups derived from presumptive acrocentric type chromosomes were observed to have much lower sex-specific differences in recombination rate than metacentric type linkage groups. Arctic charr is karyotypically the least derived species (i.e., possessing a high number of acrocentric chromosomes) and Atlantic salmon is the most derived (i.e., possessing a number of whole-arm fusions). Atlantic salmon have the largest female:male recombination ratio difference (i.e., 16.81:1) compared with rainbow trout, and Arctic charr (1.69:1). Comparisons of recombination rates between homologous segments of linkage groups among species indicated that when significant experiment-wise differences were detected (7/24 tests), recombination rates were generally higher in the species with a less-derived chromosome structure (6/7 significant comparisons). Greater similarity in linkage group syntenies were observed between Atlantic salmon and rainbow trout, suggesting their closer phylogenetic affinities, and most interspecific linkage group comparisons support a model that suggests whole chromosome arm translocations have occurred in the evolution of this group. However, some possible exceptions were detected and these findings are discussed in relation to their influence on segregation distortion patterns. We also report unusual meiotic segregation patterns in a female parent involving the duplicated (homeologous) linkage group pair 12/16 and discuss several models that may account for these patterns.Key words: linkage analysis, genetic markers, polyploidy, tetrasomic inheritance, segregation distortion, recombination rate.
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Cagnetta, Antonia, Davide Lovera, Raffaella Grasso, Nicoletta Colombo, Letizia Canepa, Filippo Ballerini, Marino Calvio, et al. "Mechanisms and Clinical Applications of Genome Instability in Multiple Myeloma." BioMed Research International 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/943096.
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Ongoing genomic instability represents a hallmark of multiple myeloma (MM) cells, which manifests largely as whole chromosome- or translocation-based aneuploidy. Importantly, although it supports tumorigenesis, progression and, response to treatment in MM patients, it remains one of the least understood components of malignant transformation in terms of molecular basis. Therefore these aspects make the comprehension of genomic instability a pioneering strategy for novel therapeutic and clinical speculations to use in the management of MM patients. Here we will review mechanisms mediating genomic instability in MM cells with an emphasis placed on pathogenic mutations affecting DNA recombination, replication and repair, telomere function and mitotic regulation of spindle attachment, centrosome function, and chromosomal segregation. We will discuss the mechanisms by which genetic aberrations give rise to multiple pathogenic events required for myelomagenesis and conclude with a discussion of the clinical applications of these findings in MM patients.
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Su, Jie, Ran Xu, Piyusha Mongia, Naoko Toyofuku, and Takuro Nakagawa. "Fission yeast Rad8/HLTF facilitates Rad52-dependent chromosomal rearrangements through PCNA lysine 107 ubiquitination." PLOS Genetics 17, no. 7 (July 22, 2021): e1009671. http://dx.doi.org/10.1371/journal.pgen.1009671.
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Gross chromosomal rearrangements (GCRs), including translocation, deletion, and inversion, can cause cell death and genetic diseases such as cancer in multicellular organisms. Rad51, a DNA strand exchange protein, suppresses GCRs by repairing spontaneous DNA damage through a conservative way of homologous recombination, gene conversion. On the other hand, Rad52 that catalyzes single-strand annealing (SSA) causes GCRs using homologous sequences. However, the detailed mechanism of Rad52-dependent GCRs remains unclear. Here, we provide genetic evidence that fission yeast Rad8/HLTF facilitates Rad52-dependent GCRs through the ubiquitination of lysine 107 (K107) of PCNA, a DNA sliding clamp. In rad51Δ cells, loss of Rad8 eliminated 75% of the isochromosomes resulting from centromere inverted repeat recombination, showing that Rad8 is essential for the formation of the majority of isochromosomes in rad51Δ cells. Rad8 HIRAN and RING finger mutations reduced GCRs, suggesting that Rad8 facilitates GCRs through 3’ DNA-end binding and ubiquitin ligase activity. Mms2 and Ubc4 but not Ubc13 ubiquitin-conjugating enzymes were required for GCRs. Consistent with this, mutating PCNA K107 rather than the well-studied PCNA K164 reduced GCRs. Rad8-dependent PCNA K107 ubiquitination facilitates Rad52-dependent GCRs, as PCNA K107R, rad8, and rad52 mutations epistatically reduced GCRs. In contrast to GCRs, PCNA K107R did not significantly change gene conversion rates, suggesting a specific role of PCNA K107 ubiquitination in GCRs. PCNA K107R enhanced temperature-sensitive growth defects of DNA ligase I cdc17-K42 mutant, implying that PCNA K107 ubiquitination occurs when Okazaki fragment maturation fails. Remarkably, K107 is located at the interface between PCNA subunits, and an interface mutation D150E bypassed the requirement of PCNA K107 and Rad8 ubiquitin ligase for GCRs. These data suggest that Rad8-dependent PCNA K107 ubiquitination facilitates Rad52-dependent GCRs by changing the PCNA clamp structure.
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Rahn, Andrea, Jolyne Drummelsmith, and Chris Whitfield. "Conserved Organization in the cps Gene Clusters for Expression of Escherichia coli Group 1 K Antigens: Relationship to the Colanic Acid Biosynthesis Locus and the cps Genes from Klebsiella pneumoniae." Journal of Bacteriology 181, no. 7 (April 1, 1999): 2307–13. http://dx.doi.org/10.1128/jb.181.7.2307-2313.1999.
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ABSTRACT Group 1 capsules of Escherichia coli are similar to the capsules produced by strains of Klebsiella spp. in terms of structure, genetics, and patterns of expression. The striking similarities between the capsules of these organisms prompted a more detailed investigation of the cps loci encoding group 1 capsule synthesis. Six strains of K. pneumoniae and 12 strains of E. coli were examined. PCR analysis showed that the clusters in these strains are conserved in their chromosomal locations. A highly conserved block of four genes,orfX-wza-wzb-wzc, was identified in all of the strains. Thewza and wzc genes are required for translocation and surface assembly of E. coli K30 antigen. The conservation of these genes points to a common pathway for capsule translocation. A characteristic JUMPstart sequence was identified upstream of each cluster which may function in conjunction with RfaH to inhibit transcriptional termination at a stem-loop structure found immediately downstream of the “translocation-surface assembly” region of the cluster. Interestingly, the sequence upstream of thecps clusters in five E. coli strains and oneKlebsiella strain indicated the presence of IS elements. We propose that the IS elements were responsible for the transfer of thecps locus between organisms and that they may continue to mediate recombination between strains.
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Ribeiro-Carvalho, C., H. Guedes-Pinto, J. S. Heslop-Harrison, and T. Schwarzacher. "Introgression of rye chromatin on chromosome 2D in the Portuguese wheat landrace 'Barbela'." Genome 44, no. 6 (December 1, 2001): 1122–28. http://dx.doi.org/10.1139/g01-088.
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The old Portuguese wheat landrace aggregate known as 'Barbela' shows good productivity under the low-fertility conditions often associated with acid soils. The use of genomic rye DNA, in combination with 45S rDNA and the repetitive sequences dpTa1 and pSc119.2 as probes, in two sequential in situ hybridization steps enabled the identification of all chromosomes in the 'Barbela' wheat lines and the detection of the introgression of rye-origin chromatin onto wheat chromosome arm 2DL in two of the lines. Amplification of microsatellite loci using published primer pairs showed that the distal segment of wheat chromosome 2DL, which was involved in the rye translocation, was deleted. The identification and characterization of small recombinant chromosome segments in wheatrye lines may allow their use in plant breeding programmes. Their presence in farmer-maintained material demonstrates the importance of maintaining, characterizing, and collecting landrace material before valuable genetic combinations are lost as uniform commercial crops are introduced.Key words: biodiversity, in situ hybridization, microsatellites, plant breeding, recombination, alien chromosomes, marker selection.
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Ulloa, Mauricio, Amanda M. Hulse-Kemp, Luis M. De Santiago, David M. Stelly, and John J. Burke. "Insights Into Upland Cotton (Gossypium hirsutum L.) Genetic Recombination Based on 3 High-Density Single-Nucleotide Polymorphism and a Consensus Map Developed Independently With Common Parents." Genomics Insights 10 (January 1, 2017): 117863101773510. http://dx.doi.org/10.1177/1178631017735104.
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High-density linkage maps are vital to supporting the correct placement of scaffolds and gene sequences on chromosomes and fundamental to contemporary organismal research and scientific approaches to genetic improvement, especially in paleopolyploids with exceptionally complex genomes, eg, upland cotton ( Gossypium hirsutum L., “2n = 52”). Three independently developed intraspecific upland mapping populations were analyzed to generate 3 high-density genetic linkage single-nucleotide polymorphism (SNP) maps and a consensus map using the CottonSNP63K array. The populations consisted of a previously reported F2, a recombinant inbred line (RIL), and reciprocal RIL population, from “Phytogen 72” and “Stoneville 474” cultivars. The cluster file provided 7417 genotyped SNP markers, resulting in 26 linkage groups corresponding to the 26 chromosomes (c) of the allotetraploid upland cotton (AD)1 arisen from the merging of 2 genomes (“A” Old World and “D” New World). Patterns of chromosome-specific recombination were largely consistent across mapping populations. The high-density genetic consensus map included 7244 SNP markers that spanned 3538 cM and comprised 3824 SNP bins, of which 1783 and 2041 were in the At and Dt subgenomes with 1825 and 1713 cM map lengths, respectively. Subgenome average distances were nearly identical, indicating that subgenomic differences in bin number arose due to the high numbers of SNPs on the Dt subgenome. Examination of expected recombination frequency or crossovers (COs) on the chromosomes within each population of the 2 subgenomes revealed that COs were also not affected by the SNPs or SNP bin number in these subgenomes. Comparative alignment analyses identified historical ancestral At-subgenomic translocations of c02 and c03, as well as of c04 and c05. The consensus map SNP sequences aligned with high congruency to the NBI assembly of Gossypium hirsutum. However, the genomic comparisons revealed evidence of additional unconfirmed possible duplications, inversions and translocations, and unbalance SNP sequence homology or SNP sequence/loci genomic dominance, or homeolog loci bias of the upland tetraploid At and Dt subgenomes. The alignments indicated that 364 SNP-associated previously unintegrated scaffolds can be placed in pseudochromosomes of the NBI G hirsutum assembly. This is the first intraspecific SNP genetic linkage consensus map assembled in G hirsutum with a core of reproducible mendelian SNP markers assayed on different populations and it provides further knowledge of chromosome arrangement of genic and nongenic SNPs. Together, the consensus map and RIL populations provide a synergistically useful platform for localizing and identifying agronomically important loci for improvement of the cotton crop.
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Fasullo, M. T., and R. W. Davis. "Direction of chromosome rearrangements in Saccharomyces cerevisiae by use of his3 recombinational substrates." Molecular and Cellular Biology 8, no. 10 (October 1988): 4370–80. http://dx.doi.org/10.1128/mcb.8.10.4370-4380.1988.
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We used the his3 recombinational substrates (his3 fragments) to direct large interchromosomal (translocations) and intrachromosomal (deletions and tandem duplications) rearrangements in the yeast Saccharomyces cerevisiae. In strains completely deleted for the wild-type HIS3 gene, his3 fragments, one containing a deletion of 5' amino acid coding sequences and the other containing a deletion of 3' amino acid coding sequences, were first placed at preselected sites by homologous recombination. His+ revertants that arose via spontaneous mitotic recombination between the two his3 fragments were selected. This strategy was used to direct rearrangements in both RAD52+ and rad52 mutant strains. Translocations occurred in the RAD52+ genetic background and were characterized by orthogonal field alternating gel electrophoresis of yeast chromosomal DNA and by standard genetic techniques. An unexpected translocation was also identified in which HIS3 sequences were amplified. Two types of tandem duplications of the GAL(7, 10, 1) locus were also directed, and one type was not observed in rad52 mutants. Recombination mechanisms are discussed to account for these differences.
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Parkin, I. A. P., A. G. Sharpe, D. J. Keith, and D. J. Lydiate. "Identification of the A and C genomes of amphidiploid Brassica napus (oilseed rape)." Genome 38, no. 6 (December 1, 1995): 1122–31. http://dx.doi.org/10.1139/g95-149.
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A genetic linkage map consisting of 399 RFLP-defined loci was generated from a cross between resynthesized Brassica napus (an interspecific B. rapa × B. oleracea hybrid) and "natural" oilseed rape. The majority of loci exhibited disomic inheritance of parental alleles demonstrating that B. rapa chromosomes were each pairing exclusively with recognisable A-genome homologues in B. napus and that B. oleracea chromosomes were pairing similarly with C-genome homologues. This behaviour identified the 10 A genome and 9 C genome linkage groups of B. napus and demonstrated that the nuclear genomes of B. napus, B. rapa, and B. oleracea have remained essentially unaltered since the formation of the amphidiploid species, B. napus. A range of unusual marker patterns, which could be explained by aneuploidy and nonreciprocal translocations, were observed in the mapping population. These chromosome abnormalities were probably caused by associations between homoeologous chromosomes at meiosis in the resynthesized parent and the F1 plant leading to nondisjunction and homoeologous recombination.Key words: genetic linkage map, homoeologous recombination, Brassica rapa, Brassica oleracea, genome organization.
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Franchini, Paolo, Andreas F. Kautt, Alexander Nater, Gloria Antonini, Riccardo Castiglia, Axel Meyer, and Emanuela Solano. "Reconstructing the Evolutionary History of Chromosomal Races on Islands: A Genome-Wide Analysis of Natural House Mouse Populations." Molecular Biology and Evolution 37, no. 10 (May 25, 2020): 2825–37. http://dx.doi.org/10.1093/molbev/msaa118.
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Abstract Chromosomal evolution is widely considered to be an important driver of speciation, as karyotypic reorganization can bring about the establishment of reproductive barriers between incipient species. One textbook example for genetic mechanisms of speciation are large-scale chromosomal rearrangements such as Robertsonian (Rb) fusions, a common class of structural variants that can drastically change the recombination landscape by suppressing crossing-over and influence gene expression by altering regulatory networks. Here, we explore the population structure and demographic patterns of a well-known house mouse Rb system in the Aeolian archipelago in Southern Italy using genome-wide data. By analyzing chromosomal regions characterized by different levels of recombination, we trace the evolutionary history of a set of Rb chromosomes occurring in different geographical locations and test whether chromosomal fusions have a single shared origin or occurred multiple times. Using a combination of phylogenetic and population genetic approaches, we find support for multiple, independent origins of three focal Rb chromosomes. The elucidation of the demographic patterns of the mouse populations within the Aeolian archipelago shows that an interplay between fixation of newly formed Rb chromosomes and hybridization events has contributed to shaping their current karyotypic distribution. Overall, our results illustrate that chromosome structure is much more dynamic than anticipated and emphasize the importance of large-scale chromosomal translocations in speciation.
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Banks, P. M., P. J. Larkin, H. S. Bariana, E. S. Lagudah, R. Appels, P. M. Waterhouse, R. I. S. Brettell, et al. "The use of cell culture for subchromosomal introgressions of barley yellow dwarf virus resistance from Thinopyrum intermedium to wheat." Genome 38, no. 2 (April 1, 1995): 395–405. http://dx.doi.org/10.1139/g95-051.
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Barley yellow dwarf virus (BYDV) resistance has been transferred to wheat from a group 7 chromosome of Thinopyrum (Agropyron) intermedium. The source of the resistance gene was the L1 disomic addition line, which carries the 7Ai-1 chromosome. The resistance locus is on the long arm of this chromosome. BYDV resistant recombinant lines were identified after three or more generations of selection against a group 7 Th. intermedium short arm marker (red coleoptile) and selection for the presence of BYDV resistance. One recombinant line produced by ph. mutant induced homoeologous pairing and 14 recombinant lines induced by cell culture have been identified. Resistance in seven of the cell culture induced recombinants has been inherited via pollen according to Mendelian segregation ratios for up to eight generations. Meiotic analysis of heterozygotes indicates that the alien chromatin in the cell culture induced recombinants is small enough to allow regular meiotic behaviour. The ph-induced recombinant was less regular in meiosis. A probe, pEleAcc2, originally isolated from Th. elongatum and that hybridizes to dispersed repeated DNA sequences, was utilised to detect Th. intermedium chromatin, which confers resistance to BYDV, in wheat backgrounds. Quantification of these hybridization signals indicated that the translocations involved a portion of alien chromatin that was smaller than the complete long arm of 7Ai-1. Restriction fragment length polymorphism analysis confirmed the loss of the short arm of 7Ai-1 and indicated the retention of segments of the long arm of 7Ai-1. Two 7Ai-1L DNA markers always assorted with the BYDV resistance. A third 7Ai-IL DNA marker was also present in seven of eight recombinants. In all recombinants except TC7, the 7Ai-1L markers replaced the 7DL markers. None of the wheat group 7 markers was missing from TC7. It is concluded that all the resistant lines are the result of recombination with wheat chromosome 7D, except line TC7, which is the result of recombination with an unidentified nongroup 7 chromosome.Key words: Triticum, Agropyron, alien genes, translocation, somatic recombination, luteovirus.
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Manthey, Glenn M., and Adam M. Bailis. "Rad51 Inhibits Translocation Formation by Non-Conservative Homologous Recombination in Saccharomyces cerevisiae." PLoS ONE 5, no. 7 (July 29, 2010): e11889. http://dx.doi.org/10.1371/journal.pone.0011889.
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Dyck, P. L., E. R. Kerber, and O. M. Lukow. "Chromosome location and linkage of a new gene (Lr33) for reaction to Puccinia recondita in common wheat." Genome 29, no. 3 (June 1, 1987): 463–66. http://dx.doi.org/10.1139/g87-080.
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A gene for resistance to Puccinia recondita, originally detected in wheat (Triticum aestivum L.) accessions PI58548, PI268454, and PI268316, has been located on the long arm of chromosome 1B, 3.1 ± 1.2 crossover units from the centromere. In a cross between the backcross line RL6057 containing this new gene, now designated Lr33, and the backcross line RL6078 containing gene Lr26, gene Lr33 is closely linked to gene Lr26 (or the translocation breakpoint) with an estimated 2.6 ± 0.8 recombination value. RL6057 and RL6078 differ in gliadin bands that are controlled by genes on the short arm of chromosome 1B or 1R. The banding difference was completely associated with the presence or absence of Lr26. Key words: Triticum, Puccinia, linkage.
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Coriton, Olivier, Dominique Barloy, Virginie Huteau, Jocelyne Lemoine, Anne-Marie Tanguy, and Joseph Jahier. "Assignment of Aegilops variabilis Eig chromosomes and translocations carrying resistance to nematodes in wheat." Genome 52, no. 4 (April 2009): 338–46. http://dx.doi.org/10.1139/g09-011.
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The allotetraploid species Aegilops variabilis Eig (2n = 28, UUSvSv) belongs to the tribe Triticeae and is closely related to wheat. One accession, Ae. variabilis No. 1, was found to be resistant to the cereal cyst nematode (CCN) and the root-knot nematode (RKN). As the genetic variability for resistance to those two pests is limited within wheat, this accession was crossed to bread wheat. Previous work enabled the development of two addition lines and two translocation lines carrying resistance. Here, we demonstrate, using genomic in situ hybridization, that there is no U–Sv interchange in the parental accession of Ae. variabilis. However, there are multiple rearrangements in the Sv chromosomes. The Ae. variabilis chromosome carrying the CreX gene for resistance to CCN combined segments with homoeology to wheat groups 1, 2, 4, and 6. The CreX gene belongs to the group 1 part and it was likely to have been introduced into chromosome 1BL at a similar location as the previously found QTL QCre.srd-1B for CCN resistance. The second Ae. variabilis chromosome carrying CreY and Rkn2 combined segments with homoeology to wheat groups 2, 4, and 7 on its short arm and group 3 on its long arm. It was designated as 3Sv. The two genes for resistance are carried by its long arm and have been transferred to wheat chromosome 3BL through homoeologous and genetically balanced recombination. Different SSR markers present in the introgressed segments could be used in marker-assisted selection.
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Sun, Jiying, Yukako Oma, Masahiko Harata, Kazuteru Kono, Hiroki Shima, Aiko Kinomura, Tsuyoshi Ikura, et al. "ATM Modulates the Loading of Recombination Proteins onto a Chromosomal Translocation Breakpoint Hotspot." PLoS ONE 5, no. 10 (October 27, 2010): e13554. http://dx.doi.org/10.1371/journal.pone.0013554.
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Korzun, V., S. Malyshev, R. A. Pickering, and A. Börner. "RFLP mapping of a gene for hairy leaf sheath using a recombinant line from Hordeum vulgare L. ×Hordeum bulbosum L. cross." Genome 42, no. 5 (October 1, 1999): 960–61. http://dx.doi.org/10.1139/g99-021.
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A gene conditioning hairy leaf sheath character, which was derived from Hordeum bulbosum and designated Hsb, was mapped using a cross between Hordeum vulgare and a H. vulgare/H. bulbosum recombinant line. The Hsb locus was tagged relative to eight RFLP markers detecting three loci on the distal part of chromosome 4HL. The map position suggests that Hsb of H. bulbosum is homoeologous to the gene Hp1 of rye (Secale cereale), which pleiotropically governs the traits hairy leaf sheath and hairy peduncle. It is proposed that the recombination break point between H. vulgare and H. bulbosum chromosomes occured at a position homoeologous compared with the 4L/5L translocation in Triticeae genomes, and may reflect a hot spot for chromosome breakage.Key words: Hordeum vulgare, Hordeum bulbosum, comparative mapping, hairy leaf sheath, RFLP.
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Kim, Changsoo, Jon S. Robertson, and Andrew H. Paterson. "Inference of subgenomic origin of BACs in an interspecific hybrid sugarcane cultivar by overlapping oligonucleotide hybridizations." Genome 54, no. 9 (September 2011): 727–37. http://dx.doi.org/10.1139/g11-038.
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Sugarcane (Saccharum spp.) breeders in the early 20th century made remarkable progress in increasing yield and disease resistance by crossing Saccharum spontaneum L., a wild relative, to Saccharum officinarum L., a traditional cultivar. Modern sugarcane cultivars have approximately 71%–83% of their chromosomes originating from S. officinarum, approximately 10%–21% from S. spontaneum, and approximately 2%–13% recombinant or translocated chromosomes. In the present work, C0t-based cloning and sequencing (CBCS) was implemented to further explore highly repetitive DNA and to seek species-specific repeated DNA in both S. officinarum and S. spontaneum. For putatively species-specific sequences, overlappping oligonucleotide probes (overgos) were designed and hybridized to BAC filters from the interspecific hybrid sugarcane cultivar ‘R570’ to try to deduce parental origins of BAC clones. We inferred that 12 967 BACs putatively originated from S. officinarum and 5117 BACs from S. spontaneum. Another 1103 BACs were hybridized by both species-specific overgos, too many to account for by conventional recombination, thus suggesting ectopic recombination and (or) translocation of DNA elements. Constructing a low C0t library is useful to collect highly repeated DNA sequences and to search for potentially species-specific molecular markers, especially among recently diverged species. Even in the absence of repeat families that are species-specific in their entirety, the identification of localized variations within consensus sequences, coupled with the site specificity of short synthetic overgos, permits researchers to monitor species-specific or species-enriched variants.
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Tomkiel, John E., Barbara T. Wakimoto, and Albert Briscoe. "The teflon Gene Is Required for Maintenance of Autosomal Homolog Pairing at Meiosis I in Male Drosophila melanogaster." Genetics 157, no. 1 (January 1, 2001): 273–81. http://dx.doi.org/10.1093/genetics/157.1.273.
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Abstract In recombination-proficient organisms, chiasmata appear to mediate associations between homologs at metaphase of meiosis I. It is less clear how homolog associations are maintained in organisms that lack recombination, such as male Drosophila. In lieu of chiasmata and synaptonemal complexes, there must be molecules that balance poleward forces exerted across homologous centromeres. Here we describe the genetic and cytological characterization of four EMS-induced mutations in teflon (tef), a gene involved in this process in Drosophila melanogaster. All four alleles are male specific and cause meiosis I-specific nondisjunction of the autosomes. They do not measurably perturb sex chromosome segregation, suggesting that there are differences in the genetic control of autosome and sex chromosome segregation in males. Meiotic transmission of univalent chromosomes is unaffected in tef mutants, implicating the tef product in a pairing-dependent process. The segregation of translocations between sex chromosomes and autosomes is altered in tef mutants in a manner that supports this hypothesis. Consistent with these genetic observations, cytological examination of meiotic chromosomes suggests a role of tef in regulating or mediating pairing of autosomal bivalents at meiosis I. We discuss implications of this finding in regard to the evolution of heteromorphic sex chromosomes and the mechanisms that ensure chromosome disjunction in the absence of recombination.
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Li, Xiaoyu, Yu Li, Hassan Karim, Yue Li, Xiaojuan Zhong, Huaping Tang, Pengfei Qi, et al. "The production of wheat – Aegilops sharonensis 1Ssh chromosome substitution lines harboring alien novel high-molecular-weight glutenin subunits." Genome 63, no. 3 (March 2020): 155–67. http://dx.doi.org/10.1139/gen-2019-0106.
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In our previous work, a novel high-molecular-weight glutenin subunit (HMW-GS) with an extremely large molecular weight from Aegilops sharonensis was identified that may contribute to excellent wheat (Triticum aestivum) processing quality and increased dough strength, and we further generated HMW-GS homozygous lines by crossing. In this study, we crossed the HMW-GS homozygous line 66-17-52 with ‘Chinese Spring’ Ph1 mutant CS ph1b to induce chromosome recombination between wheat and Ae. sharonensis. SDS-PAGE was used to identify 19 derived F2 lines with the HMW-GSs of Ae sharonensis. The results of non-denaturing fluorescence in situ hybridization (ND-FISH) indicated that lines 6-1 and 6-7 possessed a substitution of both 5D chromosomes by a pair of 1Ssh chromosomes. Further verification by newly developed 1Ssh-specific chromosome markers showed that these two lines amplified the expected fragment. Thus, it was concluded that lines 6-1 and 6-7 are 1Ssh(5D) chromosome substitution lines. The 1Ssh(5D) chromosome substitution lines, possessing alien subunits with satisfactory quality-associated structural features of large repetitive domains and increased number of subunits, may have great potential in strengthening the viscosity and elasticity of dough made from wheat flour. Therefore, these substitution lines can be used for wheat quality improvement and further production of 1Ssh translocation lines.
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Zhang, Xueyong, Yushen Dong, and Richard R. C. Wang. "Characterization of genomes and chromosomes in partial amphiploids of the hybrid Triticum aestivum × Thinopyrum ponticum by in situ hybridization, isozyme analysis, and RAPD." Genome 39, no. 6 (December 1, 1996): 1062–71. http://dx.doi.org/10.1139/g96-133.
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Genomic in situ hybridization (GISH) and Southern hybridization of genome-specific RAPD markers were used to demonstrate that the E genome (including Ee and Eb from Thinopyrum elongatum and Thinopyrum bessarabicum, respectively) and the St genome (from Pseudoroegneria species) were the two basic genomes in Thinopyrum ponticum. GISH also revealed that the centromeric region may be the critical area that discriminates the St genome from the E genome in Th. ponticum. Of the seven partial amphiploids isolated from backcrossed progenies of Triticum aestivum × Thinopyrum ponticum hybrids, two (lines 693 and 7631) have eight pairs of chromosomes from the Ee and (or) Eb genomes. Four partial amphiploids (lines 784, 68, 7430, and 40767-1) have an incomplete St genome, i.e., six pairs of chromosomes of St and one pair of chromosomes from Ee or Eb. In a heptaploid individual of the partial amphiploid 40767-2, there were four pairs of St chromosomes, one pair of St/1B Robertsonian translocation chromosomes, one pair of St/E translocation chromosomes, and one pair of Ee or Eb chromosomes. The isoelectric focusing of Est-5, Est-4, β-Amy-1, α-Amy-1, and α-Amy-2 and the RAPD data generated with 24 decamer primers on five partial amphiploids (lines 784, 693, 7631, 68, and 7430) indicated that lines 693 and 7631 had identical genomes from Th. ponticum. The partial amphiploid 784 probably had a set of chromosomes completely different from those of 693 and 7631. These results indicate that genome recombination usually occurred during the formation of new polyploid lines. Key words : Thinopyrum ponticum, wheat, partial amphiploid, GISH, isozyme, RAPD.
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Jubault, Mélanie, Anne-Marie Tanguy, Paulette Abélard, Olivier Coriton, Jean-Claude Dusautoir, and Joseph Jahier. "Attempts to induce homoeologous pairing between wheat and Agropyron cristatum genomes." Genome 49, no. 2 (February 1, 2006): 190–93. http://dx.doi.org/10.1139/g05-074.
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Agropyron cristatum (2n = 4x = 28, PPPP) possesses potentially valuable traits that could be used in wheat (Triticum aestivum) improvement through interspecific hybridization. Homoeologous pairing between wheat chromosomes and P chromosomes added to wheat in a set of wheat – A. cristatum addition lines was assessed. First, the Ph-suppressing effect of P chromosomes (except 7P) was analyzed. It was concluded that this system is polygenic with no major gene, and consequently, has no prospect in the transfer of alien genes from wild relatives. In a second step, the potential of the deletion ph1b of the Ph1 gene for inducing P–ABD pairing was evaluated. Allosyndetic associations between P and ABD genomes are very rare. This very low level of pairing is likely due to divergence in the repeated sequences between Agropyron and wheat genomes. Development of translocation lines using ionizing radiation seems to be a more suitable technique than homoeologous recombination to exploit the A. cristatum genome in wheat improvement.Key words: Triticum aestivum, Agropyron cristatum, addition line, GISH, Ph1 gene.
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Garcia, G. M., H. T. Stalker, and G. Kochert. "Introgression analysis of an interspecific hybrid population in peanuts (Arachis hypogaea L.) using RFLP and RAPD markers." Genome 38, no. 1 (February 1, 1995): 166–76. http://dx.doi.org/10.1139/g95-021.
Full textAbstract:
Forty-six introgression lines (F10C9) from a cross between Arachis hypogaea L. (2n = 4x = 40) and A. cardenasii Krapov. &W.C. Gregory (2n = 2x = 20) were analyzed for the introgression of A. cardenasii chromosome segments. Seventy-three RFLP probes and 70 RAPD primers, expressing from one to four A. cardenasii-specific bands, were used to evaluate the set of introgression lines. Thirty-four RFLP probes and 45 RAPD primers identified putative A. cardenasii introgressed chromosome segments in one or more lines. Introgressed segments were detected by RFLP analysis in 10 of the 11 linkage groups; the smallest introgressed fragments were detected by single RFLP markers and the largest were detected by three or four adjacent markers and represented introgressed segments of 30–40 cM. Similar results were obtained with RAPD markers, although markers detecting introgressed fragments could not be placed on the peanut linkage map. Introgression into both A. hypogaea genomes was detected and its implication in breeding for disease resistance is discussed.Key words: peanut, Arachis hypogaea, Arachis cardenasii, RFLPs, RAPDs, introgression, reciprocal recombination, translocation, alien gene transfer, wide cross.
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Zheng, Qi, Bin Li, Sumei Mu, Hanping Zhou, and Zhensheng Li. "Physical mapping of the blue-grained gene(s) from Thinopyrum ponticum by GISH and FISH in a set of translocation lines with different seed colors in wheat." Genome 49, no. 9 (September 2006): 1109–14. http://dx.doi.org/10.1139/g06-073.
Full textAbstract:
The original blue-grained wheat, Blue 58, was a substitution line derived from hybridization between common wheat (Triticum aestivum L., 2n = 6x = 42, ABD) and tall wheatgrass (Thinopyrum ponticum Liu & Wang = Agropyron elongatum, 2n = 10x = 70, StStEeEbEx), in which one pair of 4D chromosomes was replaced by a pair of alien 4Ag chromosomes (unknown group 4 chromosome from A. ponticum). Blue aleurone might be a useful cytological marker in chromosome engineering and wheat breeding. Cytogenetic analysis showed that blue aleurone was controlled by chromosome 4Ag. GISH analysis proved that the 4Ag was a recombination chromosome; its centromeric and pericentromeric regions were from an E-genome chromosome, but the distal regions of its two arms were from an St-genome chromosome. On its short arm, there was a major pAs1 hybridization band, which was very close to the centromere. GISH and FISH analysis in a set of translocation lines with different seed colors revealed that the gene(s) controlling the blue pigment was located on the long arm of 4Ag. It was physically mapped to the 0.71–0.80 regions (distance measured from the centromere of 4Ag). The blue color is a consequence of dosage of this small chromosome region derived from the St genome. We speculate that the blue-grained gene(s) could activate the anthocyanin biosynthetic pathway of wheat.
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Toporash, M. K., I. I. Motsnyy, A. Börner, P. Sourdille, and S. V. Chebotar. "Polymorphism in the short arm of 1R rye chromosomes in wheat lines with 1RS.1BL translocation and 1R(1B) substitution from different sources." Visnik ukrains'kogo tovaristva genetikiv i selekcioneriv 16, no. 2 (March 1, 2019): 212–16. http://dx.doi.org/10.7124/visnyk.utgis.16.2.1059.
Full textAbstract:
Aim. The short arm of 1R rye (Secale cereale L.) chromosome is widely used in the breeding of bread wheat (Triticum aestivum L.), in particular 1RS.1BL, to introsgress genes of resistance to leaf (Lr26), stem (Sr31), striped (Yr9) rusts, as well as powdery mildew (Pm8); 1RS.1AL carries Gb2/Gb6 resistance genes to the wheat aphid (Schizaphis graminum Rondani), powdery mildew (Pm17), and the Cmc4 resistance gene to the Aceria tosichella Koifer mite, which is a vector for spreading of wheat mosaic virus. The aim of the research is to reveal molecular genetic polymorphisms of short arm rye 1RS chromosomes of different origins in bread wheat lines with 1RS.1BL translocation or 1R(1B) substitution from different sources. Methods. Genetic polymorphism of lines was analyzed by using PCR with a number of rye and wheat microsatellite markers. Results. It was shown that the CWXs line has a recombinant 1RS arm that contains the chromosomes parts of 1RS of the parental lines H242/97-2 and H273/97, due to crossover event, which led to the recombination of marked loci. Conclusions. Molecular genetic polymorphism has been reviled in 1RS.1BL translocations and 1R substituted rye chromosomes of different origins in H242/97-2, CWXs, H273/97, PavonMA1, Salmon lines, as there are different alleles present at loci: Xscm9, Xtsm422, Xgwm752, Xgwm18, Taglgap. Keywords: polymorphism, 1RS.1BL translocation, PCR analysis, microsatellites markers.
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Gil-Fernández, Ana, Paul A. Saunders, Marta Martín-Ruiz, Marta Ribagorda, Pablo López-Jiménez, Daniel L. Jeffries, María Teresa Parra, et al. "Meiosis reveals the early steps in the evolution of a neo-XY sex chromosome pair in the African pygmy mouse Mus minutoides." PLOS Genetics 16, no. 11 (November 12, 2020): e1008959. http://dx.doi.org/10.1371/journal.pgen.1008959.
Full textAbstract:
Sex chromosomes of eutherian mammals are highly different in size and gene content, and share only a small region of homology (pseudoautosomal region, PAR). They are thought to have evolved through an addition-attrition cycle involving the addition of autosomal segments to sex chromosomes and their subsequent differentiation. The events that drive this process are difficult to investigate because sex chromosomes in almost all mammals are at a very advanced stage of differentiation. Here, we have taken advantage of a recent translocation of an autosome to both sex chromosomes in the African pygmy mouse Mus minutoides, which has restored a large segment of homology (neo-PAR). By studying meiotic sex chromosome behavior and identifying fully sex-linked genetic markers in the neo-PAR, we demonstrate that this region shows unequivocal signs of early sex-differentiation. First, synapsis and resolution of DNA damage intermediates are delayed in the neo-PAR during meiosis. Second, recombination is suppressed or largely reduced in a large portion of the neo-PAR. However, the inactivation process that characterizes sex chromosomes during meiosis does not extend to this region. Finally, the sex chromosomes show a dual mechanism of association at metaphase-I that involves the formation of a chiasma in the neo-PAR and the preservation of an ancestral achiasmate mode of association in the non-homologous segments. We show that the study of meiosis is crucial to apprehend the onset of sex chromosome differentiation, as it introduces structural and functional constrains to sex chromosome evolution. Synapsis and DNA repair dynamics are the first processes affected in the incipient differentiation of X and Y chromosomes, and they may be involved in accelerating their evolution. This provides one of the very first reports of early steps in neo-sex chromosome differentiation in mammals, and for the first time a cellular framework for the addition-attrition model of sex chromosome evolution.
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Bai, D., G. J. Scoles, and D. R. Knott. "Rust resistance in Triticum cylindricum Ces. (4x, CCDD) and its transfer into durum and hexaploid wheats." Genome 38, no. 1 (February 1, 1995): 8–16. http://dx.doi.org/10.1139/g95-002.
Full textAbstract:
In order to counteract the effects of the mutant genes in races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) in wheat, exploration of new resistance genes in wheat relatives is necessary. Three accessions of Triticum cylindricum Ces. (4x, CCDD), Acy1, Acy9, and Acy11, were tested with 10 races each of leaf rust and stem rust. They were resistant to all races tested. Viable F1 plants were produced from the crosses of the T. cylindricum accessions as males with susceptible MP and Chinese Spring ph1b hexaploid wheats (T. aestivum, 6x, AABBDD), but not with susceptible Kubanka durum wheat (T. turgidum var. durum, 4x, AABB), even with embryo rescue. In these crosses the D genome of hexaploid wheat may play a critical role in eliminating the barriers for species isolation during hybrid seed development. The T. cylindricum rust resistance was expressed in the F1 hybrids with hexaploid wheat. However, only the cross MP/Acy1 was successfully backcrossed to another susceptible hexaploid wheat, LMPG-6. In the BC2F2 of the cross MP/Acy1//LMPG-6/3/MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 (infection types (IT) 1=, 1, or 1+; addition line 1) or stem rust race 15B-1 (IT 1 or 1+; addition line 2) were selected. Rust tests and examination of chromosome pairing of the F1 hybrids and the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. cylindricum C-genome chromosomes rather than on the D-genome chromosomes. The T. cylindricum chromosome in addition line 2 was determined to be chromosome 4C through the detection of RFLPs among the genomes using a set of homoeologous group-specific wheat cDNA probes. Addition line 1 was resistant to the 10 races of leaf rust and addition line 2 was resistant to the 10 races of stem rust, as was the T. cylindricum parent. The added C-genome chromosomes occasionally paired with hexaploid wheat chromosomes. Translocation lines with rust resistance (2n = 21 II) may be obtained in the self-pollinated progeny of the addition lines through spontaneous recombination of the C-genome chromosomes and wheat chromosomes. Such translocation lines with resistance against a wide spectrum of rust races should be potentially valuable in breeding wheat for rust resistance.Key words: wheat, Triticum cylindricum, rust resistance, gene transfer, addition line, molecular cytogenetics.