scholarly journals Effects of autosomal inversions on meiotic exchange in distal and proximal regions of the X chromosome in a natural population of Drosophila melanogaster

1994 ◽  
Vol 63 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Paul D. Sniegowski ◽  
Anne Pringle ◽  
Kimberly A. Hughes
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Population ◽  
X Chromosome ◽  
Natural Populations ◽  
Element Abundance ◽  
Recombination Rates ◽  
Interchromosomal Effect ◽  
Naturally Occurring ◽  
Study Population ◽  
Transposable Element Abundance

SummaryWe have investigated the interchromosomal effect of the naturally-occurring paracentric inversions In(2L)t and In(3R)P on meiotic recombination in two regions of the X chromosome in Drosophila melanogaster. Previous authors have suggested that the rate of recombination at the tip of the X chromosome may be substantially higher in some natural populations than values measured in the laboratory, due to the interchromosomal effect of heterozygous autosomal inversions. This suggestion was motivated by observations that transposable elements are not as common at the tip of the X chromosome as predicted by recent research relating reduced meiotic exchange to increased element abundance in D. melanogaster. We examined the effects of heterozygous In(2L)t and In(3R)P on recombination at both the tip and base of the X chromosome on a background of isogenic major chromosomes from a natural population. Both inversions substantially increased the rate of recombination at the base; neither one affected recombination at the tip. The results suggest that the presence of inversions in the study population does not elevate rates of crossing over at the tip of the X chromosome. The relevance of these results to ideas relating transposable element abundance to recombination rates is discussed.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

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 Hybrid dysgenesis-induced quantitative variation on the X chromosome of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 627-636
Author(s):  
C Q Lai ◽  
T F Mackay
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Quantitative Traits ◽  
Natural Populations ◽  
Quantitative Variation ◽  
Hybrid Dysgenesis ◽  
X Chromosomes ◽  
Bristle Number ◽  
Seven Generations ◽  
Polygenic Variation

Abstract To determine the ability of the P-M hybrid dysgenesis system of Drosophila melanogaster to generate mutations affecting quantitative traits, X chromosome lines were constructed in which replicates of isogenic M and P strain X chromosomes were exposed to a dysgenic cross, a nondysgenic cross, or a control cross, and recovered in common autosomal backgrounds. Mutational heritabilities of abdominal and sternopleural bristle score were in general exceptionally high-of the same magnitude as heritabilities of these traits in natural populations. P strain chromosomes were eight times more mutable than M strain chromosomes, and dysgenic crosses three times more effective than nondysgenic crosses in inducing polygenic variation. However, mutational heritabilities of the bristle traits were appreciable for P strain chromosomes passed through one nondysgenic cross, and for M strain chromosomes backcrossed for seven generations to inbred P strain females, a result consistent with previous observations on mutations affecting quantitative traits arising from nondysgenic crosses. The new variation resulting from one generation of mutagenesis was caused by a few lines with large effects on bristle score, and all mutations reduced bristle number.

scholarly journals Studies of esterase 6 in Drosophila melanogaster: XIV. Variation of esterase 6 levels controlled by unlinked genes in natural populations

1984 ◽  
Vol 43 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Craig S. Tepper ◽  
Anne L. Terry ◽  
James E. Holmes ◽  
Rollin C. Richmond
Keyword(s):  
Drosophila Melanogaster ◽  
Structural Gene ◽  
X Chromosome ◽  
Genetic Background ◽  
Natural Populations ◽  
Regulatory Elements ◽  
Regulatory Locus ◽  
The Third ◽  
Esterase 6 ◽  
Activity Modifiers

SUMMARYThe esterase 6 (Est-6) locus in Drosophila melanogaster is located on the third chromosome and is the structural gene for a carboxylesterase (E.C.3.1.1.1) and is polymorphic for two major electromorphs (slow and fast). Isogenic lines containing X chromosomes extracted from natural populations and substituted into a common genetic background were used to detect unlinked factors that affect the activity of the Est-6 locus. Twofold activity differences of esterase 6 (EST 6) were found among males from these derived lines, which differ only in their X chromosome. These unlinked activity modifiers identify possible regulatory elements. Immunoelectrophoresis was used to estimate quantitatively the levels of specific cross-reacting material in the derived lines. The results show that the variation in activity is due to differences in the amount of EST 6 present. The data are consistent with the hypothesis that there is at least one locus on the X chromosome that regulates the synthesis of EST 6 and that this regulatory locus may be polymorphic in natural populations.

scholarly journals GENETIC ANALYSIS OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER IN JAPAN. II. THE MEASUREMENT OF FITNESS AND FITNESS COMPONENTS IN HOMOZYGOUS LINES

Genetics ◽  
1984 ◽  
Vol 108 (1) ◽  
pp. 213-221 ◽  
Author(s):  
Tsuneyuki Yamazaki ◽  
Yasuko Hirose
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Analysis ◽  
Natural Population ◽  
Natural Populations ◽  
Distribution Patterns ◽  
Developmental Time ◽  
Fitness Components ◽  
Isogenic Lines ◽  
Genetic Structures

ABSTRACT Fifty lethal-free, sterility-free isogenic lines of Drosophila melanogaster that were randomly sampled from a natural population were tested for net fitness and other components of fitness by competition with D. hydei. Larval viability and developmental time were also measured using the balanced marker method. Distribution patterns of these fitness components were similar, but correlation between the fitness components varied depending on the combinations used. The highest correlations were obtained between net fitness and productivity (rp = 0.6987, rg = 0.9269). The correlation between net fitness and total larval viability was much lower (rp = 0.1473 and rg = 0.2171). These results indicate that measuring net fitness, not just a component of fitness, is necessary for the good understanding of the genetic structures of natural populations.

scholarly journals Lack of underdominance in a naturally occurring pericentric inversion in Drosophila melanogaster and its implications for chromosome evolution.

Genetics ◽  
1991 ◽  
Vol 129 (3) ◽  
pp. 791-802
Author(s):  
J A Coyne ◽  
S Aulard ◽  
A Berry
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Genetic Drift ◽  
Related Species ◽  
Pericentric Inversion ◽  
Chromosome Evolution ◽  
Natural Populations ◽  
Crossing Over ◽  
Closely Related Species ◽  
Naturally Occurring

Abstract In(2LR)PL is a large pericentric inversion polymorphic in populations of Drosophila melanogaster on two Indian Ocean islands. This polymorphism is puzzling: because crossing over in female heterokaryotypes produces inviable zygotes, such inversions are thought to be underdominant and should be quickly eliminated from populations. The observed fixation for such inversions among related species has led to the idea that genetic drift can cause chromosome evolution in opposition to natural selection. We found, however, that In(2LR)PL is not underdominant for fertility, as heterokaryotypic females produce perfectly viable eggs. Genetic analysis shows that the lack of underdominance results from the nearly complete absence of crossing over in the inverted region. This phenomenon is probably caused by mechanical and not genetic factors, because crossing over is not suppressed in In(2LR)PL homokaryotypes. Our observations do not support the idea that the fixation of pericentric inversions among closely related species implies the action of genetic drift overcoming strong natural selection in very small populations. If chromosome arrangements vary in their underdominance, it is those with the least disadvantage as heterozygotes, like In(2LR)PL, that will be polymorphic or fixed in natural populations.

scholarly journals Analysis of linkage disequilibria between allozyme loci in natural populations of Drosophila melanogaster

1978 ◽  
Vol 32 (3) ◽  
pp. 215-229 ◽  
Author(s):  
Charles H. Langley ◽  
Diana B. Smith ◽  
F. M. Johnson
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Analysis Of Variance ◽  
Natural Populations ◽  
Correlation Coefficients ◽  
Absolute Value ◽  
Linkage Disequilibria ◽  
Enzyme Loci ◽  
Allozyme Loci

SUMMARYLinkage disequilibria between pairs of 8 polymorphic enzyme loci (αGpdh, Mdh, Adh, Est-6, Pgm, Odh, Est-C and Acph) in some 100 natural population samples of Drosophila melanogaster were examined. The estimates of linkage disequilibrium were made from zygotic frequencies. The magnitude of linkage disequilibria are small and similar to those in previous reports. Variation in linkage disequilibrium among related subpopulations was analysed by analysis of variance of the correlation coefficients. Despite the small absolute value of linkage disequilibrium there is a suggestion of a correlation among related subpopulations. The magnitude of linkage disequilibrium was observed to be positively correlated with linkage. Two cage populations were observed to demonstrate large amounts of linkage disequilibrium between closely linked loci in contrast to the situation in natural populations. This is attributable to the finite sizes of these cage populations.

scholarly journals Genetic Variation in Rates of Nondisjunction: Association of Two Naturally Occurring Polymorphisms in the Chromokinesin nod With Increased Rates of Nondisjunction in Drosophila melanogaster

Genetics ◽  
1999 ◽  
Vol 152 (4) ◽  
pp. 1605-1614 ◽  
Author(s):  
Michael E Zwick ◽  
Jennifer L Salstrom ◽  
Charles H Langley
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Chromosome Segregation ◽  
Natural Populations ◽  
Intermediate Frequency ◽  
Female Meiosis ◽  
X Chromosomes ◽  
Naturally Occurring ◽  
High Level ◽  
Female Specific

Abstract Genetic variation in nondisjunction frequency among X chromosomes from two Drosophila melanogaster natural populations is examined in a sensitized assay. A high level of genetic variation is observed (a range of 0.006-0.241). Two naturally occurring variants at the nod locus, a chromokinesin required for proper achiasmate chromosome segregation, are significantly associated with an increased frequency of nondisjunction. Both of these polymorphisms are found at intermediate frequency in widely distributed natural populations. To account for these observations, we propose a general model incorporating unique opportunities for meiotic drive during female meiosis. The oötid competition model can account for both high mean rates of female-specific nondisjunction in Drosophila and humans as well as the standing genetic variation in this critical fitness character in natural populations.

scholarly journals LINKAGE DISEQUILIBRIUM IN NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. SEASONAL VARIATION

Genetics ◽  
1977 ◽  
Vol 86 (2) ◽  
pp. 447-454
Author(s):  
Charles H Langley ◽  
Kazuko Ito ◽  
Robert A Voelker
Keyword(s):  
Drosophila Melanogaster ◽  
Seasonal Variation ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Natural Populations ◽  
The Other ◽  
Allozyme Loci

ABSTRACT Linkage disequilibrium among ten polymorphic allozyme loci and polymorphic inversions on chromosomes 2 and 3 in a natural population of Drosophila melanogaster was examined early and late in the annual season. Similar to previous studies, little linkage disequilibrium was observed among allozymes. The two significant cases that were observed in the first sample behaved in a contradictory way. One declined much more rapidly than expected due simply to recombination; the other declined slowly as expected. There was little change in allozyme or inversion frequencies during the season.

scholarly journals Linkage Disequilibrium Patterns Across a Recombination Gradient in African Drosophila melanogaster

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1289-1305 ◽  
Author(s):  
Peter Andolfatto ◽  
Jeffrey D Wall
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Gene Conversion ◽  
X Chromosome ◽  
Large Population ◽  
Detailed Examination ◽  
Crossing Over ◽  
Recombination Rates ◽  
A Genome ◽  
Mutation Drift Equilibrium

Abstract Previous multilocus surveys of nucleotide polymorphism have documented a genome-wide excess of intralocus linkage disequilibrium (LD) in Drosophila melanogaster and D. simulans relative to expectations based on estimated mutation and recombination rates and observed levels of diversity. These studies examined patterns of variation from predominantly non-African populations that are thought to have recently expanded their ranges from central Africa. Here, we analyze polymorphism data from a Zimbabwean population of D. melanogaster, which is likely to be closer to the standard population model assumptions of a large population with constant size. Unlike previous studies, we find that levels of LD are roughly compatible with expectations based on estimated rates of crossing over. Further, a detailed examination of genes in different recombination environments suggests that markers near the telomere of the X chromosome show considerably less linkage disequilibrium than predicted by rates of crossing over, suggesting appreciable levels of exchange due to gene conversion. Assuming that these populations are near mutation-drift equilibrium, our results are most consistent with a model that posits heterogeneity in levels of exchange due to gene conversion across the X chromosome, with gene conversion being a minor determinant of LD levels in regions of high crossing over. Alternatively, if levels of exchange due to gene conversion are not negligible in regions of high crossing over, our results suggest a marked departure from mutation-drift equilibrium (i.e., toward an excess of LD) in this Zimbabwean population. Our results also have implications for the dynamics of weakly selected mutations in regions of reduced crossing over.

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