scholarly journals Selective Recombination System in Bombyx mori. I. Chromosome Specificity of the Modification Effect

Genetics ◽  
1987 ◽  
Vol 117 (3) ◽  
pp. 521-531
Author(s):  
Hiroyasu Ebinuma
Keyword(s):  
Bombyx Mori ◽  
Recombination Rate ◽  
Recombination Frequency ◽  
Genetic System ◽  
System Model ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Recombination Rates ◽  
Recombination System ◽  
The Family

ABSTRACT The effect of modifiers on recombination frequency between Ze and lem loci on chromosome 3 to elucidate the chromosome specificity of modification and the distribution of modifiers using Bombyx mori lines selected for high (H) and low (L) recombination rates between the pS and Y loci in chromosome 2 was investigated. By crossing to the Z (Ze lem/++) line, the recombination rate between the pS and Y loci in chromosome 2 was decreased from 28.18 to 23.33 in the H line and was increased from 4.92 to 16.05 in the L line. On the other hand, the recombination rate between the Ze and lem loci in chromosome 3 was increased from 16.21 to 20.21 in the Z line by crossing to the H line, but also increased to 19.02 by crossing to the L line. The significant correlation observed between the transformed recombination rates of chromosomes 2 and 3 in the (Z × L) × L backcross indicated that there were common factors modifying recombination frequency in chromosomes 2 and 3 or different factors linked to the same chromosomes. In the family of L × [(Z × L) × L] backcross, the distribution of transformed recombination rates indicated that there were several factors in the remaining chromosomes which were modifying recombination frequency in chromosome 2 but not in chromosome 3. It was also indicated that these factors were linked to different chromosomes than are the factors modifying recombination frequency in chromosome 3. In order to interpret these results, one genetic system model controlling recombination that consists of general and local recombination modifiers was proposed. The evolution of dynamic genetic systems that would effectively reduce recombinational load without reducing the advantage of recombination was discussed.

scholarly journals THE GENETIC SYSTEM CONTROLLING RECOMBINATION IN THE SILKWORM

Genetics ◽  
1981 ◽  
Vol 99 (2) ◽  
pp. 231-245
Author(s):  
Hiroyasu Ebinuma ◽  
Narumi Yoshitake
Keyword(s):  
Chromosomal Aberrations ◽  
Recombination Frequency ◽  
Genetic System ◽  
Chromosome 2 ◽  
Chromosome 5 ◽  
Recombination Rates ◽  
Heterozygous Condition ◽  
In Trans ◽  
The Mean ◽  
In Cis

ABSTRACT The nature of recombination modifiers was investigated in Bombyx mori lines selected for high (H) and low (L) recombination rates between the pS and Y loci in chromosome 2. Since the mean recombination rates for the H × L and L × H F1 crosses were approximately intermediate between those of high and low lines, the cytoplasmic maternal effect and difference in the activity of recombination modifiers between marked and unmarked second chromosomes were not detected. The H × (L × H), H × (H × L), L × (L × H) and L × (H × L) backcrosses indicated the presence of additive and dominance effects of marked and unmarked second chromosomes and the remaining chromosomes.——Recombination rates between the pS and Y loci in chromosome 2 and half-nonrecombination rates between the pe and re loci in chromosome 5 of high and low lines indicated that these recombination modifiers caused changes in the recombination frequency between pS and Y in chromosome 2, but not between pe and re in chromosome 5.——There were no differences in viability between individuals having the second chromosomes of the recombinant types [pS +, pY (H); pS +, + Y (L)] and those of the nonrecombinant types [pS Y, p + (H); pS Y, + + (L)] in both high and low lines. Mean recombination rates measured in cis [pS Y/p + (H); pS Y/+ + (L)] and trans [pS +/p Y (H); pS +/+ Y (L)] males were the same in the high but not in the low line. No segregation of a single recombination modifier was indicated by the distribution of recombination rates measured in trans males [pS +/p Y (H); pS +/+ Y (L)] of high and low lines. Accordingly, the recombination modifiers distributed on chromosome 2 in the heterozygous condition were not gross chromosomal aberrations, but polygenic factors in the low line.

scholarly journals VARIATION FOR GENETIC RECOMBINATION AMONG TOMATO PLANTS REGENERATED FROM THREE TISSUE CULTURE SYSTEMS

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1164e-1164 ◽  
Author(s):  
Michael E. Compton ◽  
Richard E. Veilleux
Keyword(s):  
Tissue Culture ◽  
Genetic Recombination ◽  
Shoot Tips ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Recombination Rates ◽  
Culture Systems ◽  
Thin Cell Layers ◽  
Cell Layers ◽  
Map Distance

Genetic recombination rates of hybrid plants regenerated from three tissue culture. systems were compared by backcrossing regenerated plants with mutant parents and comparing the observed crossover frequencies with those expected based on control plants raised from seed. Increased recombination rates and map distances were observed among plants from micropropagated shoot tips (4.5%-5.9%), cotyledon calli (3.7%-8.5%), and thin cell layers (2.8%-6.5%) between the sunny (sy) and baby leaf syndrome (bls) markers which flank the centromere on chromosome 3. Conversely, a decrease in map distance was observed between bls and the solanifolia (sf) locus which is more distal to the centromere on the same arm of chromosome 3 as bls. Increased map distance among plants regenerated from micropropagated shoot tips, cotyledon calli, and thin cell layers was also observed between white virescence (wv) and anthocyanin reduced (are) loci on chromosome 2.

Variation for genetic recombination among tomato plants regenerated from three tissue culture systems

Genome ◽  
1991 ◽  
Vol 34 (5) ◽  
pp. 810-817 ◽  
Author(s):  
Michael E. Compton ◽  
Richard E. Veilleux
Keyword(s):  
Tissue Culture ◽  
Genetic Recombination ◽  
Shoot Tips ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Recombination Rates ◽  
Culture Systems ◽  
Hybrid Plants ◽  
Map Distance ◽  
Pedicel Explants

Shoot morphogenesis was compared among two tomato inbred lines, two mutant lines, and their eight reciprocal F1 hybrids in three tissue culture systems. The number of shoots per explant was greatest on tomato pedicel explants, intermediate on cotyledon calli, and poor on micropropagated shoot tips. Genetic recombination rates of F1 hybrid plants regenerated from three tissue culture systems were analyzed by backcrossing the regenerated plants with mutant parents and comparing the observed crossover frequencies with those expected based on control plants raised from seed. Increased recombination rates and map distance were observed among plants from micropropagated shoot tips (18.8%), cotyledon calli (17.3%), and pedicel explants (13.5%) between the markers sunny (sy) and baby leaf syndrome (bls), which flank the centromere on chromosome 3. Conversely, decreased recombination rates and map distance were observed between bls and the locus solanifolia (sf), which is more distal to the centromere on the same arm of chromosome 3 as bls. Increased recombination rates and map distance among plants from micropropagated shoot tips, cotyledon calli, and pedicel explants were also observed between the loci white virescence (wv) and anthocyanin reduced (are) on chromosome 2.Key words: genetic recombination, tomato, Lycopersicon esculentum, pedicel explants, micropropagation, callus culture, plant regeneration.

High Frequency Recombination During the Sexual Cycle of Dictyostelium discoideum

Genetics ◽  
1998 ◽  
Vol 148 (4) ◽  
pp. 1829-1832 ◽  
Author(s):  
David Francis
Keyword(s):  
Dictyostelium Discoideum ◽  
Genetic Map ◽  
High Frequency ◽  
Cell Biology ◽  
Physical Map ◽  
Genetic System ◽  
Sexual Cycle ◽  
Chromosome 2 ◽  
New Combinations ◽  
Restriction Sites

Abstract Analysis of Dictyostelium development and cell biology has suffered from the lack of an ordinary genetic system whereby genes can be arranged in new combinations. Genetic exchange between two long ignored strains, A2Cycr and WS205 is here reexamined. Alleles which differ in size or restriction sites between these two strains were found for seven genes. Six of these are in two clusters on chromosome 2. Frequencies of recombinant progeny indicate that the genetic map of the two mating strains is colinear with the physical map recently worked out for the standard nonsexual strain, NC4. The rate of recombination is high, about 0.1% per kilobase in three different regions of chromosome 2. This value is comparable to rates found in yeast, and will permit fine dissection of the genome.

scholarly journals Microsatellite Variation and Recombination Rate in the Human Genome

Genetics ◽  
2000 ◽  
Vol 156 (3) ◽  
pp. 1285-1298 ◽  
Author(s):  
Bret A Payseur ◽  
Michael W Nachman
Keyword(s):  
Recombination Rate ◽  
Microsatellite Polymorphism ◽  
Published Data ◽  
Strong Positive Correlation ◽  
Background Selection ◽  
Recombination Rates ◽  
Microsatellite Variation ◽  
Positive Correlation ◽  
Genome Recombination ◽  
Neutral Mutations

Abstract Background (purifying) selection on deleterious mutations is expected to remove linked neutral mutations from a population, resulting in a positive correlation between recombination rate and levels of neutral genetic variation, even for markers with high mutation rates. We tested this prediction of the background selection model by comparing recombination rate and levels of microsatellite polymorphism in humans. Published data for 28 unrelated Europeans were used to estimate microsatellite polymorphism (number of alleles, heterozygosity, and variance in allele size) for loci throughout the genome. Recombination rates were estimated from comparisons of genetic and physical maps. First, we analyzed 61 loci from chromosome 22, using the complete sequence of this chromosome to provide exact physical locations. These 61 microsatellites showed no correlation between levels of variation and recombination rate. We then used radiation-hybrid and cytogenetic maps to calculate recombination rates throughout the genome. Recombination rates varied by more than one order of magnitude, and most chromosomes showed significant suppression of recombination near the centromere. Genome-wide analyses provided no evidence for a strong positive correlation between recombination rate and polymorphism, although analyses of loci with at least 20 repeats suggested a weak positive correlation. Comparisons of microsatellites in lowest-recombination and highest-recombination regions also revealed no difference in levels of polymorphism. Together, these results indicate that background selection is not a major determinant of microsatellite variation in humans.

scholarly journals Dissection of closely linked QTLs controlling stigma exsertion rate in rice by substitution mapping

2021 ◽  
Author(s):  
Quanya Tan ◽  
Chengshu Wang ◽  
Xin Luan ◽  
Lingjie Zheng ◽  
Yuerong Ni ◽  
...  
Keyword(s):  
Complex Trait ◽  
Epistatic Effect ◽  
Open Reading Frames ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Substitution Mapping ◽  
Mapping Strategy ◽  
Stigma Exsertion ◽  
Important Trait ◽  
Stigma Exsertion Rate

Abstract Key message Through substitution mapping strategy, two pairs of closely linked QTLs controlling stigma exsertion rate were dissected from chromosomes 2 and 3 and the four QTLs were fine mapped. Abstract Stigma exsertion rate (SER) is an important trait affecting the outcrossing ability of male sterility lines in hybrid rice. This complex trait was controlled by multiple QTLs and affected by environment condition. Here, we dissected, respectively, two pairs of tightly linked QTLs for SER on chromosomes 2 and 3 by substitution mapping. On chromosome 2, two linkage QTLs, qSER-2a and qSER-2b, were located in the region of 1288.0 kb, and were, respectively, delimited to the intervals of 234.9 kb and 214.3 kb. On chromosome 3, two QTLs, qSER-3a and qSER-3b, were detected in the region of 3575.5 kb and were narrowed down to 319.1 kb and 637.3 kb, respectively. The additive effects of four QTLs ranged from 7.9 to 9.0%. The epistatic effect produced by the interaction of qSER-2a and qSER-2b was much greater than that of qSER-3a and qSER-3b. The open reading frames were identified within the maximum intervals of qSER-2a, qSER-2b and qSER-3a, respectively. These results revealed that there are potential QTL clusters for SER in the two regions of chromosome 2 and chromosome 3. Fine mapping of the QTLs laid a foundation for cloning of the genes of SER.

scholarly journals Patterns of DNA Variability at X-Linked Loci in Mus domesticus

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1303-1316
Author(s):  
Michael W Nachman
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
House Mouse ◽  
Recombination Rate ◽  
Nucleotide Diversity ◽  
Mus Domesticus ◽  
Substantial Variation ◽  
Intraspecific Polymorphism ◽  
Recombination Rates ◽  
Interspecific Divergence

Introns of four X-linked genes (Hprt, Plp, Glra2, and Amg) were sequenced to provide an estimate of nucleotide diversity at nuclear genes within the house mouse and to test the neutral prediction that the ratio of intraspecific polymorphism to interspecific divergence is the same for different loci. Hprt and Plp lie in a region of the X chromosome that experiences relatively low recombination rates, while Glra2 and Amg lie near the telomere of the X chromosome, a region that experiences higher recombination rates. A total of 6022 bases were sequenced in each of 10 Mus domesticus and one M. caroli. Average nucleotide diversity (π) for introns within M. domesticus was quite low (π = 0.078%). However, there was substantial variation in the level of heterozygosity among loci. The two telomeric loci, Glra2 and Amg, had higher ratios of polymorphism to divergence than the two loci experiencing lower recombination rates. These results are consistent with the hypothesis that heterozygosity is reduced in regions with lower rates of recombination, although sampling of additional genes is needed to establish whether there is a general correlation between heterozygosity and recombination rate as in Drosophila melanogaster.

scholarly journals Rearrangements of the DNA in Carbon Ion-Induced Mutants of Arabidopsis thaliana

Genetics ◽  
2001 ◽  
Vol 157 (1) ◽  
pp. 379-387 ◽  
Author(s):  
Naoya Shikazono ◽  
Atsushi Tanaka ◽  
Hiroshi Watanabe ◽  
Shigemitsu Tano
Keyword(s):  
Arabidopsis Thaliana ◽  
Nonhomologous End Joining ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Carbon Ions ◽  
Induced Mutations ◽  
End Joining ◽  
Carbon Ion ◽  
Induced Mutants ◽  
Dna Strand

Abstract To elucidate the nature of structural alterations in plants, three carbon ion-induced mutations in Arabidopsis thaliana, gl1-3, tt4(C1), and ttg1-21, were analyzed. The gl1-3 mutation was found to be generated by an inversion of a fragment that contained GL1 and Atpk7 loci on chromosome 3. The size of the inverted fragment was a few hundred kilobase pairs. The inversion was found to accompany an insertion of a 107-bp fragment derived from chromosome 2. The tt4(C1) mutation was also found to be due to an inversion. The size of the intervening region between the breakpoints was also estimated to be a few hundred kilobase pairs. In the case of ttg1-21, it was found that a break occurred at the TTG1 locus on chromosome 5, and reciprocal translocation took place between it and chromosome 3. From the sequences flanking the breakpoints, the DNA strand breaks induced by carbon ions were found to be rejoined using, if present, only short homologous sequences. Small deletions were also observed around the breakpoints. These results suggest that the nonhomologous end-joining (NHEJ) pathway operates after plant cells are exposed to ion particles.

scholarly journals Modeling Linkage Disequilibrium and Identifying Recombination Hotspots Using Single-Nucleotide Polymorphism Data

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2213-2233 ◽  
Author(s):  
Na Li ◽  
Matthew Stephens
Keyword(s):  
Linkage Disequilibrium ◽  
Recombination Rate ◽  
Population Sample ◽  
Simulated Data ◽  
Region Of Interest ◽  
Population Data ◽  
Recombination Rates ◽  
Single Nucleotide ◽  
Recombination Hotspots ◽  
Genomic Regions

AbstractWe introduce a new statistical model for patterns of linkage disequilibrium (LD) among multiple SNPs in a population sample. The model overcomes limitations of existing approaches to understanding, summarizing, and interpreting LD by (i) relating patterns of LD directly to the underlying recombination process; (ii) considering all loci simultaneously, rather than pairwise; (iii) avoiding the assumption that LD necessarily has a “block-like” structure; and (iv) being computationally tractable for huge genomic regions (up to complete chromosomes). We examine in detail one natural application of the model: estimation of underlying recombination rates from population data. Using simulation, we show that in the case where recombination is assumed constant across the region of interest, recombination rate estimates based on our model are competitive with the very best of current available methods. More importantly, we demonstrate, on real and simulated data, the potential of the model to help identify and quantify fine-scale variation in recombination rate from population data. We also outline how the model could be useful in other contexts, such as in the development of more efficient haplotype-based methods for LD mapping.

Chromosome polymorphism in natural populations of Anopheles quadrimaculatus Say species A and B

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 138-146 ◽  
Author(s):  
P. E. Kaiser ◽  
J. A. Seawright ◽  
B. K. Birky
Keyword(s):  
X Chromosome ◽  
Southeastern United States ◽  
Polytene Chromosomes ◽  
Natural Populations ◽  
Chromosome 3 ◽  
Chromosome Polymorphism ◽  
Chromosome 2 ◽  
Anopheles Quadrimaculatus ◽  
The Right ◽  
Maculipennis Complex

Ovarian polytene chromosomes from eight populations of Anopheles quadrimaculatus in the southeastern United States were observed for chromosomal polymorphisms. Two sibling species, species A and B, each with intraspecific inversions, were distinguished. Species A correlates with the previously published standard maps for salivary gland and ovarian nurse-cell polytene chromosomes. Species A was found at all eight collection sites, and five of these populations also contained species B. Three inversions on the right arm of chromosome 3 were observed in species A. Species B contained a fixed inversion on the X chromosome, one fixed and one floating inversion on the left arm of chromosome 2, and one fixed and one floating inversion on the right arm of chromosome 3. The fixed inversion on the X chromosome makes this the best diagnostic chromosome for distinguishing species A and B. An unusual dimorphism in the left arm of chromosome 3, found in both species A and B, contained two inversions. The heterokaryotypes, as well as two distinct homokaryotypes, were seen in all of the field populations. Intraspecific clinal variations in the frequencies of the species A inversions were noted. The Florida populations were practically devoid of inversions, the Georgia and Alabama populations contained some inversions, and the Arkansas population was mostly homozygous for two of the inversions. The phylogenetic relationships of species A and B to the Maculipennis complex (Nearctic) are discussed.Key words: Anopheles, inversion, populations, chromosome polymorphism, phylogenetics.

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