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Topic: Segregation distortion

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	Intragenomic conflict - Wikipedia, the free encyclopedia
		However, there is one type of gene, called segregation distorter, that "cheats" during meiosis or gametogenesis and thus is present in more than half of the functional gametes.
		Segregation distorters that are present in sexual chromosomes (as the X chromosome in several Drosophila species) are denominated sex-ratio distorters, as they induce a sex-ratio bias in the offspring of the carrier individual.
		The segregation distorter set is composed by the allele Killer (in the Killer locus) and the allele Resistant (in the Target locus), while its rival set is composed by the alleles Non-killer and Non-resistant.
	en.wikipedia.org /wiki/Meiotic_drive (979 words)

	BGN 21: Effect of the Ga2 gene on segregation distortion in barley (Site not responding. Last check: 2007-11-03)
		Segregation of the esterase isozyme genotypes in the B
		The segregation was significantly deviated from a ratio of 1:1.
		Distorted segregation of the esterase isozyme genotypes in barley (Hordeum vulgare L.).
	wheat.pw.usda.gov /ggpages/bgn/21/a21-20.html (395 words)

	Evolution - A-Z - Segregation distortion
		A segregation distortion gene produces a distortion in normal segregation in favor of itself, so that chromosomes bearing this gene are over-represented in an organism's offspring.
		This produces a distortion in favor of chromosomes containing the segregation distortion gene.
		The segregation distorter gene was first found in fruitfly (Drosophila) stocks from Wisconsin and Baja California.
	www.blackwellpublishing.com /ridley/a-z/Segregation_distortion.asp (209 words)

	The Utility of the Diploid Map in Alfalfa Improvement
		Since not all markers are expected to segregate in all crosses, the more markers there are on the map, the better the chances are of finding segregating markers in specific crosses, and in specific chromosomal locations.
		SDRFs segregate in a 1:1 ratio, resembling the mapping of a diploid backcross population.
		Segregation ratios for 18 to 50% of the markers deviated from the expected ratios, and tended to favor heterozygous genotypes.
	www.naaic.org /TAG/TAGpapers/Bouton/DiploidMapPaper.htm (4087 words)

	ARS \| Publication request: Aflp-Ssr Maps of Maize X Teosinte and Maize X Maize: Comparison of Map Length and ... (Site not responding. Last check: 2007-11-03)
		Segregating individuals obtained form these populations were used for a comparative genetic analysis of their genomes and chromosome regions that may possess genes conferring flooding tolerance.
		The expression and segregation of flooding tolerance in the two populations, and the association of molecular markers to various genes controlling this trait, suggest that these genes can be readily transferred to corn by a marker-assisted breeding program.
		Genetic linkage analysis of the molecular markers across the two populations suggests segregation distortion in particular regions of chromosomes 4, 5, and 8 in the B64 x teosinte population and on chromosome 9 in the B64 x Na4 population.
	ars.usda.gov /research/publications/publications.htm?seq_no_115=176991 (657 words)

	Genetics and Molecular Biology - Skewed RAPD markers in linkage maps of Citrus (Site not responding. Last check: 2007-11-03)
		The position of the markers with a skewed segregation in the linkage groups (at the end of the groups or between markers with the expected segregation) was correlated with the conservation of the distances and the order of non-skewed segregation markers.
		The segregation of the markers in the progeny studied showed low recombination frequencies and are therefore located very close to one another in the linkage groups.
		When the markers with a skewed segregation were removed, there was a proportional decrease in the absolute number of linked markers, in the number of linked markers per linkage group, in the size of the linkage groups, and in the total length of the maps of both varieties.
	www.scielo.br /scielo.php?script=sci_arttext&pid=S1415-47572004000300021&lng=en&nrm=iso&tlng=en (2971 words)

	21. Distorted segregation of Acp-1 for acid phosphatase in a wide cross of rice
		Distorted F`2` ratios are often observed for mrphological markers in crosses between distantly related rice varieties.
		The occurrence of similar patterns at the three locations differing in environmental conditions suggests that segregation distortion is genotype-inherent and not influenced much by environment.
		This suggests that distortion is due to competition of pollen grains for fertilization.
	www.gramene.org /newsletters/rice_genetics/rgn11/v11p106.htm (447 words)

	PAG-VI: MOLECULAR MAPPING OF SEGREGATION DISTORTION LOCI IN Aegilops tauschii (Site not responding. Last check: 2007-11-03)
		Distorted segregation ratios of molecular and morphological markers are often observed in progeny of inter- and intra-specific hybrids.
		Three regions of segregation distortion were identified on chromosome 5D and were further analyzed in two sets of reciprocal backcross populations.
		Extreme distortion of marker segregation ratios was observed in populations in which the F
	www.intl-pag.org /6/abstracts/31.html (250 words)

	CSIRO PUBLISHING - Australian Journal of Agricultural Research
		Segregation distortion was estimated in several populations where sufficient information from genetic markers was available.
		In particular, clustering of distorted loci at specific chromosome regions appeared to be associated with the presence of alien introgressions in one of the parents.
		Providing such distortions are recognised in the models used, these populations provide powerful tools for extensive mapping studies to determine the genetic factors controlling grain quality traits and other wheat characters of interest.
	www.publish.csiro.au /nid/40/paper/AR01043.htm (375 words)

	Options Menu
		When you choose this command, the segregation codes which are assigned to a locus depend on the phenotypes recorded for that locus.
		Segregation distortion, or differential viability, describes the situation in which the phenotypes at a locus do not appear in the expected proportions.
		Segregation distortion affects linkage tests (Garcia-Dorado and Gallego, 1992) and the estimation of recombination fractions (Lorieux et al., 1995a,b).
	www.mapmanager.org /QTX/Menus8a.html (1359 words)

	Birgid Schlindwein's Hypermedia Glossary Of Genetic Terms - Search results
		Deviation from the expected Mendelian proportion of individuals in a given genotypic class within a segregating population.
		Segregation distortion has been documented in a wide range of organisms, including plants, in which species or strain hybrids exhibit preferential dysfunction of gametes carrying one allelic class.
		Segregation may occur at the first or second division of meiosis, or at the first mitosis after meiosis (postmeiotic segregation).
	hal.weihenstephan.de /genglos/asp/genreq.asp?nr=393 (339 words)

	ARS \| Publication request: The Use of Rapd Markers for Lentil Genetic Mapping and the Evaluation of Distorted F2 ... (Site not responding. Last check: 2007-11-03)
		Distorted segregation of markers was noted for a portion of the loci and indicated unequal segregation or survival of certian individuals.
		In cross 1, 83% of the RAPD markers showed segregation distortion, which was also observed for isozyme and morphological loci.
		Seventy-eight segregation loci were analyzed for linkage, at a LOD score-3.0, resulted in 28 RAPD, one RFLP, one morphological and three eoligonucleotide markers, which were assigned to 9 linkage groups spanning 206 cM.
	www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=100368 (320 words)

	BGN 22: Distorted segregation of the lys3a mutant in barley kernels
		A distorted segregation of high lysine gene Iys3a located in chromosome 7 was found in several crosses (Ahokas, 1979, 1988; Doll and Oram, 1989).
		Segregation of Iys3a mutant kernels in F2 populations of reciprocal crosses between Riso 1508 and Beecher.
		Nakagahra, M. Genetic mechanism on the distorted segregation of marker genes belonging to the eleventh linkage group in cultivated rice.
	wheat.pw.usda.gov /ggpages/bgn/22/a22-19.html (523 words)

	untitled (Site not responding. Last check: 2007-11-03)
		Despite their systematic advantage at the gamete level, none of the well-known segregation distorters spreads to fixation since they induce severe negative fitness effects at the individual level.
		By means of a population genetical model, we analyse the various factors that determine the success of a segregation distorter in a metapopulation.
		Therefore, distorters with intermediate segregation ratios may reach the highest frequency in the metapopulation as a result of the opposing forces of gamete, individual and group selection.
	www.life.umd.edu /faculty/wilkinson/ZOOL608V/groups\groupsel.html (5555 words)

	BGN 23: Segregation distortion at the Est5 locus in doubled haploid lines of barley (Site not responding. Last check: 2007-11-03)
		Further, segregation of isozyme alleles at the Est5 locus was examined in F2 seedlings of two cross combinations shown the significant distortion.
		From these results, it is clear that the segregation distortion at the Est5 locus occurs only in the DH lines derived from some specific crosses, and that the distortion cannot be detected in F2 populations of the same crosses.
		Segregation of esterase genotypes at the Est5 locus in F2 populations.
	wheat.pw.usda.gov /ggpages/bgn/23/a23-08.html (352 words)

	Untitled Document
		We were not expecting segregation for so many traits or to see occasional multifoliolate leaves, but we have seen all these things before in crosses involving M. sativa, coerulea, and falcata, Hence, our goal now is a unified understanding of genomic relationships in Medicago broadly.
		We were prepared to search for hybrid families on the basis of the segregation for the Jemalong leaf marking in the F2; however, every F2 family segregated.
		They report that the gene for direction of coiling maps on chromosome 7 and had no segregation distortion in their cross.
	www.medicago-reports.org /f2segregationdata.htm (1505 words)

	BioMed Central \| Full text \| Increasing incidence of Type 1 diabetes - role for genes?
		Irrespective of the effect on incidence, if there is segregation distortion and it has been acting over generations, it could have contributed to maintaining, or even accumulating diabetic alleles in the population.
		In model M2 segregation distortion is assumed to have been acting at approximately the same rate through (some) generations; the time period of interest ranges from the 1930s to the present.
		Excluding the possible transmission distortion effect, the formation of zygotes is random, and there is no homozygosity deficiency (which, on the contrary, is known to exist in HLA in certain populations, as shown in [39,40]).
	www.biomedcentral.com /1471-2156/5/5 (4190 words)

	Genetics and Molecular Biology - The SCA1 (Spinocerebellar ataxia type 1) and MJD (Machado-Joseph disease) CAG repeats ... (Site not responding. Last check: 2007-11-03)
		We investigated allele segregation in mother-child pairs, and estimated the frequencies of SCA1 and MJD alleles in a sample of clinically normal individuals from the northeastern region of the State of São Paulo, Brazil.
		For estimating segregation distortion, we prepared a program that allows to determine the inherited allele by direct genotype analysis of the trios, and records which one of the alleles, the larger or the smaller, was transmitted.
		In the segregation distortion analysis, 367 trios were analyzed for the SCA1 locus, including 734 meioses (Table 1), and 879 trios for the MJD locus, totaling 1758 meioses (Table 2).
	www.scielo.br /scielo.php?pid=S1415-47572003000200002&script=sci_arttext&tlng=en (2693 words)

	OhioLINK ETD: Fryan, Raymond
		The results show that local variation of carbon composition in the range of 0.01 to 0.02 weight percent can cause heat treatment distortion as large as ∼120\ μm, depending on the severity and spatial distribution of the segregation present.
		The mechanism by which chemical segregation causes distortion is the imbalance of transformational stresses during quenching.
		In general, positive segregation near the quarter radius region of the ring appears to be most effective for creating a large shape change
	www.ohiolink.edu /etd/view.cgi?case1061905405 (326 words)

	[No title]
		The segregation distortion might be due to the bining method used in genotyping at this locus.
		It is not clear whether the observed difference in the transmission of allele 182 from heterozygous parents is due to random chance or segregation distortion at this locus.
		The observed segregation distortion at the GR1K1 locus might be due to the bining method used in genotyping (Reich, personal communication).
	www-rcf.usc.edu /~fsun/Publication/Gaw11/gaw11_sun.doc (2095 words)

	A Generalization of Theory on the Evolution of Modifier Genes (Site not responding. Last check: 2007-11-03)
		Further analogy between the behavior of this model and that of segregation distortion models is seen in cases tested numerically where the fitnesses of the two selected homozygotes are different.
		Because segregation and syngamy are acting to transform also the modifier genotype, the case of selfing involves transformation of the transformation type, in addition to variation that is not linear.
		In the one case where transformation of the transformation type was explored, the case of modifiers of segregation distortion, it was found that even with linear variation in the transformations, increased transformation could evolve.
	dynamics.org /~altenber/PAPERS/GTEMG/PhD.Ch3.excerpt.html (2388 words)

	Segregation Distortion in Hybrids Between the Bogota and USA Subspecies of Drosophila pseudoobscura -- Orr and Irving ...
		Segregation Distortion in Hybrids Between the Bogota and USA Subspecies of Drosophila pseudoobscura -- Orr and Irving 169 (2): 671 -- Genetics
		segregation distortion is similar to that of hybrid male sterility
		distortion cannot be the sole cause of hybrid male sterility.
	www.genetics.org /cgi/content/full/169/2/671 (5984 words)

	Grewal et al. Machado-Joseph Disease
		We performed a likelihood-based analysis of segregation distortion in the single sperm data using the SPERMSEG program of McPeek (1999) "SPERMSEG: analysis of segregation distortion in sigle-sperm data" American Journal of Human Genetics 65:1195-1197.
		The mutant MJD1 allele showed reduced amplification, as is sometimes the case with large repeats, which could potentially result in a biased estimate of segregation probability and hide any segregation distortion in favor of that allele.
		Thus, using the linked marker, we do not expect the estimate of segregation distortion to be biased, particularly not in the direction of hiding segregation distortion in favor the the mutant MJD1.
	galton.uchicago.edu /~mcpeek/data/grewaletal.html (473 words)

	Douglas R. Taylor - Evolutionary Biology
		This segregation distortion allows selfish elements to spread in populations, despite the fact that they are often harmful to the organisms in which they reside.
		There is a wide variety of selfish elements that distort the sex ratio in natural populations; Y-chromosome meiotic drive, supernumerary chromosomes, cytoplasmic microorganisms and organelle genes (cytoplasmic male sterility in plants).
		This so-called “intragenomic conflict” has been found in nearly all systems involving sex ratio distortion, and could be important for the evolution of many aspects of sexual reproduction including the evolutionary stability of Mendelian segregation itself.
	www.people.virginia.edu /~drt3b/research/selfishGenElements.php (292 words)

	Disomic Inheritance, Suppressed Recombination, and Allelic Interactions Govern Apospory in Buffelgrass as Revealed by ...
		Segregation distortion through female gametophytes in interspecific hybrids of tetraploid wheat as revealed by RAPD analysis.
		Segregation distortion and linkage of Citrus and Poncirus isozyme genes.
		Distorted segregation and linkage of alcohol dehydrogenase genes in Camellia japonica (Theaceae).
	crop.scijournals.org /cgi/content/full/42/5/1688 (4371 words)

	Truncated RanGAP Encoded by the Segregation Distorter Locus of Drosophila -- Merrill et al. 283 (5408): 1742 -- Science
		Truncated RanGAP Encoded by the Segregation Distorter Locus of Drosophila -- Merrill et al.
		Segregation Distorter (SD) in Drosophila melanogaster is a naturally occurring meiotic drive system in which the SD chromosome
		Segregation distortion induced by wild-type RanGAP in Drosophila.
	www.sciencemag.org /cgi/content/abstract/283/5408/1742?ck=nck (597 words)

	Yuichiro Hiraizumi
		In 1967 while visiting Wisconsin he showed (with Hartl and Crow) that segregation distortion was due to nonfunctional sperm.
		Negative segregation distortion in the SD system of Drosophila melanogaster: A challenge to the concept of differential sensitivity of Rsp alleles.
		Segregation distorter (SD) in Drosophila melanogaster: Genetics and molecular analyses.
	www.utexas.edu /faculty/council/2004-2005/memorials/hiraizumi/hiraizumi.html (1817 words)

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