scholarly journals Complete absence of linkage disequilibrium between enzyme loci in natural populations of Drosophila ananassae

Genetika ◽  
2014 ◽  
Vol 46 (1) ◽  
pp. 227-234 ◽  
Author(s):  
Sanjay Kumar ◽  
A.K. Singh
Keyword(s):  
Linkage Disequilibrium ◽  
Natural Populations ◽  
Drosophila Ananassae ◽  
Crossing Over ◽  
Enzyme Loci ◽  
Random Occurrence

Linkage disequilibrium has been studied among three linked enzyme loci of second chromosome of D. ananassae collected from five natural populations. Each of the three enzyme loci, that is Acph1, Acph 2 and Xdh was represented by two distinct alleles and in three genotypic forms. Thus nine genotypic combinations were recorded for each enzyme pair. The results clearly show absence of non-random occurrence of different genotypic combinations in all the populations studied. The occurrence of all possible genotypic combinations indicates enough frequency of crossing over among these enzyme loci. The absence of linkage disequilibrium in this study thus indicates that selection did not play any role and free recombination among the genes resulted random occurrence of all combinations.

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.

Crossing over does occur in males of Drosophila ananassae from natural populations

Genome ◽  
2012 ◽  
Vol 55 (7) ◽  
pp. 505-511 ◽  
Author(s):  
Beatriz Goñi ◽  
Muneo Matsuda ◽  
Masa-Toshi Yamamoto ◽  
Carlos R. Vilela ◽  
Yoshiko N. Tobari
Keyword(s):  
Natural Populations ◽  
Drosophila Ananassae ◽  
Crossing Over ◽  
Cytological Analysis ◽  
Wild Type ◽  
Cytological Evidence ◽  
Type Strains ◽  
Chromosome Breakages ◽  
Brazilian Populations

Spontaneous crossing over in males of Drosophila ananassae has been well demonstrated using F1 individuals from crosses between marker stocks and wild type strains. However, the question of its occurrence in males from natural populations remained open. Here we present the cytological evidence that crossing over does occur in males of D. ananassae from two Brazilian populations, sampled nearly 21 years apart, and in two recently sampled populations, one from Indonesia and one from Okinawa, Japan. Cytological analysis of meiosis in males collected from nature and in sons of females from the same population inseminated in nature revealed the presence of chiasmata, inversion chiasmata, and isosite chromosome breakages in the diplotene cells in all sampled populations. These data demonstrate that reciprocal and nonreciprocal exchanges and chromosome breakages, previously reported as related events of male crossing over, do occur at variable frequencies among males from natural populations.

scholarly journals GENIC VERSUS CHROMOSOMAL VARIATION IN NATURAL POPULATIONS OF DROSOPHILA SUBOBSCURA

Genetics ◽  
1974 ◽  
Vol 78 (4) ◽  
pp. 1223-1244
Author(s):  
E Zouros ◽  
C B Krimbas ◽  
S Tsakas ◽  
M Loukas
Keyword(s):  
Linkage Disequilibrium ◽  
Natural Populations ◽  
Genetic Data ◽  
Drosophila Subobscura ◽  
Lower Degree ◽  
Island Population ◽  
Chromosomal Variation ◽  
Random Drift ◽  
Enzyme Loci ◽  
High Degree

ABSTRACT Gametic frequencies in one mainland and one island population of D. subobscura were obtained by means of extracting wild chromosomes and subsequently analyzing them for inversions and allozymes. The high degree of cytological heterogeneity which characterizes these populations is not reflected in the genetic data. Two cases of non-random association were observed among eighteen pair-wise comparisons involving gene alleles and inversions to which the locus is linked. In both cases exchange of alleles at the locus is completely suppressed by the inversions. Four cases of linkage disequilibrium were detected among eighteen pairs of loci; two of them could best be explained as transient associations generated by random drift. The results suggest that disequilibria among enzyme loci are not widespread in natural populations—Populations with a lower degree of chromosomal variation are genetically as variable as populations with a higher degree of chromosomal variation. This observation does not support the hypothesis that selection in marginal homokaryotypic populations is for specialized homozygous genotypes.

scholarly journals Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 457-467 ◽  
Author(s):  
Z W Luo ◽  
S H Tao ◽  
Z-B Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Allele Frequency ◽  
Random Mating ◽  
Natural Populations ◽  
Polymorphic Marker ◽  
Marker Locus ◽  
Model Parameters ◽  
Phenotypic Variance ◽  
Wide Range ◽  
Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

scholarly journals Joint Linkage and Linkage Disequilibrium Mapping in Natural Populations

Genetics ◽  
2001 ◽  
Vol 157 (2) ◽  
pp. 899-909
Author(s):  
Rongling Wu ◽  
Zhao-Bang Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Complex Traits ◽  
Positional Cloning ◽  
Genome Structure ◽  
Natural Populations ◽  
Linkage Disequilibrium Mapping ◽  
Linkage Disequilibria ◽  
Time Simulation ◽  
New Strategy ◽  
Fisher Scoring Algorithm

Abstract A new strategy for studying the genome structure and organization of natural populations is proposed on the basis of a combined analysis of linkage and linkage disequilibrium using known polymorphic markers. This strategy exploits a random sample drawn from a panmictic natural population and the open-pollinated progeny of the sample. It is established on the principle of gene transmission from the parental to progeny generation during which the linkage between different markers is broken down due to meiotic recombination. The strategy has power to simultaneously capture the information about the linkage of the markers (as measured by recombination fraction) and the degree of their linkage disequilibrium created at a historic time. Simulation studies indicate that the statistical method implemented by the Fisher-scoring algorithm can provide accurate and precise estimates for the allele frequencies, recombination fractions, and linkage disequilibria between different markers. The strategy has great implications for constructing a dense linkage disequilibrium map that can facilitate the identification and positional cloning of the genes underlying both simple and complex traits.

scholarly journals Network Analysis of Linkage Disequilibrium Reveals Genome Architecture in Chum Salmon

2020 ◽  
Vol 10 (5) ◽  
pp. 1553-1561 ◽  
Author(s):  
Garrett McKinney ◽  
Megan V. McPhee ◽  
Carita Pascal ◽  
James E. Seeb ◽  
Lisa W. Seeb
Keyword(s):  
Population Structure ◽  
Linkage Disequilibrium ◽  
Network Analysis ◽  
Chum Salmon ◽  
Sex Chromosome ◽  
Natural Populations ◽  
Population Substructure ◽  
Chromosome Inversion ◽  
Genomic Features ◽  
Chromosome Inversions

Many studies exclude loci that exhibit linkage disequilibrium (LD); however, high LD can signal reduced recombination around genomic features such as chromosome inversions or sex-determining regions. Chromosome inversions and sex-determining regions are often involved in adaptation, allowing for the inheritance of co-adapted gene complexes and for the resolution of sexually antagonistic selection through sex-specific partitioning of genetic variants. Genomic features such as these can escape detection when loci with LD are removed; in addition, failing to account for these features can introduce bias to analyses. We examined patterns of LD using network analysis to identify an overlapping chromosome inversion and sex-determining region in chum salmon. The signal of the inversion was strong enough to show up as false population substructure when the entire dataset was analyzed, while the effect of the sex-determining region on population structure was only obvious after restricting analysis to the sex chromosome. Understanding the extent and geographic distribution of inversions is now a critically important part of genetic analyses of natural populations. Our results highlight the importance of analyzing and understanding patterns of LD in genomic dataset and the perils of excluding or ignoring loci exhibiting LD. Blindly excluding loci in LD would have prevented detection of the sex-determining region and chromosome inversion while failing to understand the genomic features leading to high-LD could have resulted in false interpretations of population structure.

scholarly journals Linkage disequilibrium in experimental populations of Drosophila simulans: a test of the random drift hypothesis

1987 ◽  
Vol 50 (3) ◽  
pp. 187-193
Author(s):  
Catherine Montchamp-Moreau ◽  
Mariano Katz
Keyword(s):  
Linkage Disequilibrium ◽  
Genetic Drift ◽  
Natural Populations ◽  
Aldehyde Oxidase ◽  
Drosophila Simulans ◽  
Random Drift ◽  
Esterase 6 ◽  
Experimental Populations ◽  
Experimental Values ◽  
Neutralist Hypothesis

SummaryLinkage disequilibrium between five polymorphic enzymic loci of the third chromosome (Esterase-6, Phosphoglucomutase, Esterase-C, Aldehyde Oxidase and Acid Phosphatase) was studied in experimental populations of Drosophila simulans. Gametic data were obtained by mating sampled males with homozygous females at the five loci. Four cage populations were initiated with flies caught from natural populations. Extensive linkage disequilibrium was detected after 25 or 34 generations. The effective size of these populations was estimated about 400. Monte-Carlo simulations were performed in order to determine whether the observed disequilibria could be due to genetic drift. The observed probability distribution of the experimental values of r (the gametic correlation coefficient) was consistent with the distribution expected under random genetic drift. Our results are thus in accordance with the neutralist hypothesis.

RELATIONS BETWEEN FACTORS CONTROLLING CROSSING OVER AND MUTABILITY IN MALES OF DROSOPHILA ANANASSAE

Genetics ◽  
1983 ◽  
Vol 104 (1) ◽  
pp. 95-112
Author(s):  
Claude W Hinton
Keyword(s):  
Regional Distribution ◽  
The Other ◽  
Drosophila Ananassae ◽  
Crossing Over ◽  
The Third

ABSTRACT Several stocks, selected because they carried previously identified factors governing either crossing over in males or mutability, were examined to determine whether the effects of these factors are restricted to one or the other process. Neither of two dominant enhancers of male crossing over had detectable effects on Minute mutation frequencies among progenies of assayed F1 males. Genetically equivalent F1 males monitored for crossing over showed no unequivocal effect of either of three mutators (two dominant and one extrachromosomal) or of a suppressor of mutability. However, one combination of a dominant crossover enhancer with a dominant mutator showed synergistic increases in both crossover and Minute frequencies, and the possibility exists that a single extrachromosomally transmitted element suppresses both male crossing over and mutability. This suppressor element (or elements) had been previously diagnosed in the pc stock which, in this study, was discovered to have also a dominant enhancer of male crossing over and a dominant mutator occupying separable loci in the third chromosome. The pc enhancer of male crossing over differs from the dominant enhancer in another stock with respect to the regional distribution of crossovers, and the pc mutator is distinguished from another 3-linked mutator by its preferential induction of mutations at the Delta locus.

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