scholarly journals DYNAMICS OF CORRELATED GENETIC SYSTEMS. V. RATES OF DECAY OF LINKAGE DISEQUILIBRIA IN EXPERIMENTAL POPULATIONS OF DROSOPHILA MELANOGASTER

Genetics ◽  
1980 ◽  
Vol 94 (1) ◽  
pp. 217-234
Author(s):  
M T Clegg ◽  
J F Kidwell ◽  
C R Horch
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Isocitrate Dehydrogenase ◽  
Gene Frequency ◽  
Experimental Results ◽  
Frequency Distributions ◽  
Marker Loci ◽  
Experimental Populations ◽  
Selective Effects ◽  
F Statistics

ABSTRACT The dynamic behavior of four-locus gametic frequency distributions was studied in five replicate cage populations of Drosophila melanogaster for up to 50 generations. The joint frequency distributions were resolved into gene freqcencies and various disequilibrium measures. In addition, F statistics for marginal single-locus genotypic frequency distributions were followed through time. The gene frequency, disequilibrium and F statistics were obtained for four chromosome 3 enzyme marker loci [isocitrate dehydrogenase (3-27.1), esterase4 (3-36.8). phosphoglucomutase (343.4) and esterase-c (3-49.0)]. The initial structure of the experimental populations featured random mating proportions, and two complementary gametic types with respect to the marker loci, thus assuring complete pairwise linkage disequilibrium among the markers.—The experimental results indicate: (1) the between-replicate variance in gene frequency varied substantially among loci, with isocitrate dehydrogenase showing the greatest between-replicate variance, and esterase-C the least. (2) The F statistics initially were strongly negative but decayed to the neighborhood ofzero for all marker lociexcept esterase-C. The rate at which the F statistics approached zero varied among the marker loci, indicating substantial differences in the distribution of selective effects along the chromosome. The centromeric region, marked by esterase-C, shows the strongest selective effects. (3)The rate of decay 3flinkage disequilibrium was much faster than expected for pairs of neutral loci, averaging 1.82times the neutral rate over all replicates and pairs of loci. This acceleration, which was observed for all six pairwise combinations of loci, was interpreted asresulting from the interaction bctween selection and recombination. Our experimental results are consistent with many investigations of linkage disequilibrium in natural populations of Drosophila melanogasler that show little or no disequilibrium among enzyme loci. (4) Afortuitous contamination of two cages revealed an apparent regulatory interaction between the migrant and nonmigrant chromosomes at the esterase-C locus. The migrant chromosomes were very rapidly absorbed into the recipient populations, despite this interaction. This result suggests that the dynamics of migration in populations may be phenomenologically richer than anticipated by simple theory.

scholarly journals Linkage disequilibrium in natural and experimental populations of Drosophila melanogaster.

Genetics ◽  
1988 ◽  
Vol 120 (4) ◽  
pp. 1043-1051
Author(s):  
Z Smit-McBride ◽  
A Moya ◽  
F J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Assay Method ◽  
Effective Population ◽  
Population Mixing ◽  
Locus Pair ◽  
Two Samples ◽  
In The Wild ◽  
Population Sizes ◽  
Experimental Populations

Abstract We have studied linkage disequilibrium in Drosophila melanogaster in two samples from a wild population and in four large laboratory populations derived from the wild samples. We have assayed four polymorphic enzyme loci, fairly closely linked in the third chromosome: Sod Est-6, Pgm, and Odh. The assay method used allows us to identify the allele associations separately in each of the two homologous chromosomes from each male sampled. We have detected significant linkage disequilibrium between two loci in 16.7% of the cases in the wild samples and in 27.8% of the cases in the experimental populations, considerably more than would be expected by chance alone. We have also found three-locus disequilibria in more instances than would be expected by chance. Some disequilibria present in the wild samples disappear in the experimental populations derived from them, but new ones appear over the generations. The effective population sizes required to generate the observed disequilibria by randomness range from 40 to more than 60,000 individuals in the natural population, depending on which locus pair is considered, and from 100 to more than 60,000 in the experimental populations. These population sizes are unrealistic; the fact that different locus-pairs yield disparate estimates within the same population argues against the likelihood that the disequilibria may have arisen as a consequence of population bottlenecks. Migration, or population mixing, cannot be excluded as the process generating the disequilibria in the wild samples, but can in the experimental populations. We conclude that linkage disequilibrium in these populations is most likely due to natural selection acting on the allozymes, or on loci very tightly linked to them.

scholarly journals Polymorphism at the G6PD and 6PGD loci in Drosophila melanogaster: I. Evidence for selection in experimental populations

1977 ◽  
Vol 30 (3) ◽  
pp. 221-236 ◽  
Author(s):  
R. Bijlsma ◽  
W. van Delden
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Background ◽  
Gene Frequency ◽  
Low Frequencies ◽  
Isozyme Loci ◽  
Experimental Populations ◽  
Frequency Changes ◽  
Experimental Cage

SUMMARYGene frequency changes were followed in 17 experimental cage populations of Drosophila melanogaster polymorphic for the two loci G6PD and 6PGD. From these cages it was observed that selection was favouring the F alleles of both loci when the cages were started with low frequencies of these alleles (0·20F and 0·50F). A viability experiment and an extinction experiment also provided evidence that the F alleles of both loci were favoured. It is argued that the observed selection is not due to selective differences in genetic background of the different alleles, but is acting on the isozyme loci themselves.

scholarly journals STUDIES OF ESTERASE-6 IN DROSOPHILA MELANOGASTER. II. THE GENETICS AND FREQUENCY DISTRIBUTIONS OF NATURALLY OCCURRING VARIANTS STUDIED BY ELECTROPHORETIC AND HEAT STABILITY CRITERIA

Genetics ◽  
1979 ◽  
Vol 93 (2) ◽  
pp. 461-478 ◽  
Author(s):  
Bruce J Cochrane ◽  
Rollin C Richmond
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Frequency ◽  
Allelic Variation ◽  
Natural Populations ◽  
Heat Stability ◽  
Allozyme Variation ◽  
Frequency Distributions ◽  
Naturally Occurring ◽  
Esterase 6 ◽  
Different Populations

ABSTRACT Measurements of the electrophoretic mobility and thermostability of esterase-6 allozymes have been used to determine the amount of allelic variation at the esterase-6 locus in Drosophila melanogaster. We studied 39.8 homozygous lines obtained from four natural populations. Use of a spectro-photometric assay for esterase-6 activity has allowed precise quantitation of heat-stability variants. Using these methods, eight putative alleles were detected within the two most common electrophoretic classes. Analyses of F1 and F2 progeny show that the behavior of stability variants is consistent with the hypothesis that this variation is due to allelic variation at the Est-6 locus. Analyses of the gene-frequency distributions within and between populations show (1) that observed allele-frequency distributions do not deviate significantly from those expected for neutral variants, and (2) that there is little evidence for an increase in apparent divergence of the different populations at the genotypic o r phenotypic levels when the additional variation detected is considered. These findings suggest that gene-frequency analysis alone is unlikely to resolve the question of the selective significance of allozyme variation.

scholarly journals GENETIC DIFFERENTIATION BETWEEN GEOGRAPHICALLY DISTANT POPULATIONS OF DROSOPHILA MELANOGASTER

Genetics ◽  
1982 ◽  
Vol 101 (2) ◽  
pp. 235-256
Author(s):  
Rama S Singh ◽  
Donal A Hickey ◽  
Jean David
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Differentiation ◽  
Gene Frequency ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Clinal Variation ◽  
Significant Genetic Differentiation ◽  
African Populations ◽  
Latitudinal Clines ◽  
North And South

ABSTRACT We have studied allozyme variation at 26 gene loci in nine populations of Drosophila melanogaster originating on five different continents. The distant populations show significant genetic differentiation. However, only half of the loci studied have contributed to this differentiation; the other half show identical patterns in all populations. The genetic differentiation in North American, European and African populations is correlated with the major climatic differences between north and south. These differences arise mainly from seven loci that show gene-frequency patterns suggestive of latitudinal clines in allele frequencies. The clinal variation is such that subtropical populations are more heterozygous than temperate populations. These results are discussed in relation to the selectionist and neutralist hypotheses of genetic variation in natural populations.

Phosphoglucomutase (PGM) and Esterase-6 (EST-6) alleles in Drosophila melanogaster: An attempt to detect linkage disequilibrium

Genetica ◽  
1978 ◽  
Vol 49 (2-3) ◽  
pp. 225-227 ◽  
Author(s):  
G. Trippa ◽  
G. A. Danieli ◽  
R. Costa ◽  
R. Scozzari
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Esterase 6
Sign in / Sign up

Export Citation Format

Share Document