scholarly journals A CONTRIBUTION TO THE STUDY OF LINKAGE DISEQUILIBRIUM IN DROSOPHILA MELANOGASTER

1976 ◽  
Vol 18 (4) ◽  
pp. 739-745 ◽  
Author(s):  
S. Alahiotis ◽  
M. Pelecanos ◽  
A. Zacharopoulou
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Environmental Conditions ◽  
Gene Pool ◽  
Ecological Factors ◽  
Random Drift ◽  
Different Populations ◽  
Food Medium

Linkage disequilibrium was detected in 12 out of 30 cases involving gene alleles and inversions in three cage populations and in a natural population of Drosophila melanogaster from Greece. The cage populations possessed practically the same gene pool at their origin and were maintained simultaneously under the effects of the ecological factors "food medium" and "humidity". It is discussed that the correlation of the same direction found between the frequencies of nonallelic elements of Adh locus and In(2L)22D-34A or In(2R)52A-56F in such different populations as American, Japanese (Mukai et al., 1971, 1974; Langley et al., 1974) and Greek, as well as cage populations under different environmental conditions, could be attributed to the effect of epistatic selection. Moreover, it seems that the In(2L)22D-34A has a tendency to interact genetically with the α-Gpdh locus, particularly when the populations are maintained under crowding conditions. However, further data are needed to assess whether other cases of the observed nonrandom associations can be better explained as transient associations generated by random drift, or as the result of epistatic selection.

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 Extensive linkage disequilibrium in the achaete-scute complex of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 126 (1) ◽  
pp. 121-129
Author(s):  
J N Macpherson ◽  
B S Weir ◽  
A J Leigh Brown
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Nucleotide Diversity ◽  
Single Site ◽  
Restriction Map ◽  
X Chromosomes ◽  
Linkage Disequilibria ◽  
Restriction Sites ◽  
Gametic Association

Abstract We have analyzed the level of gametic association between restriction map variants in a sample of 44 X chromosomes from a natural population of Drosophila melanogaster. Of 21 pairwise tests involving 7 restriction map polymorphisms in the yellow-achaete-scute complex, 17 were found to be significant, including some between restriction sites over 80 kb apart. Three-way linkage disequilibria and their variances were also estimated for all 35 three-way comparisons between these loci. Twelve such tests were found to be significant, again spanning distances of up to 80 kb on the restriction map. Only 9 of a possible 128 haplotypes were represented in the sample and 8 of these could be linked together by changes at a single site. The strength of these associations at y-ac-sc is unusual by comparison with studies on other regions of the genome of D. melanogaster, and is consistent with the very low level of recombination which has been reported for the complex. However, our estimate of nucleotide diversity in the region is not significantly different from those made for some other loci in this species.

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 in the white locus region of Drosophila melanogaster

1993 ◽  
Vol 62 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Naohiko T. Miyashita ◽  
Montserrat Aguadé ◽  
Charles H. Langley
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Natural Populations ◽  
Restriction Enzymes ◽  
Transcriptional Unit ◽  
Similar Degree ◽  
Significant Linkage Disequilibrium ◽  
White Locus ◽  
Different Populations ◽  
Significant Linkage

SummaryLinkage disequilibrium between molecular polymorphisms in a 10 kb region in the white locus of Drosophila melanogaster, revealed with a battery of four-cutter restriction enzymes, was investigated in 266 lines sampled from seven natural populations around the world. A total of 73 (35 restriction site, 37 insertion/deletion and 1 inversion) polymorphisms were detected, of which 55 non-unique polymorphisms were analysed for linkage disequilibrium. Clustering of significant linkage disequilibrium was observed in the transcriptional unit of the white locus as in Miyashita & Langley (1988). It was shown that about two thirds of the 2-locus combinations showing significant linkage disequilibrium have similar degree and direction of association over different populations. Despite lower divergence in allelic frequencies of molecular polymorphisms among populations, an increase in the proportion of 2-locus pairs showing significant linkage disequilibrium is observed in the transcriptional unit. Large values of Ohta's D measure ratio (1982 a, b) cluster in the transcriptional unit, and correspond to significant linkage disequilibria. Although the exact molecular mechanism is not clear, these results suggest that epistatic selection is responsible for significant linkage disequilibrium in the transcriptional unit of this locus

scholarly journals A STUDY OF LINKAGE DISEQUILIBRIUM IN POPULATIONS OF DROSOPHILA MELANOGASTER

Genetics ◽  
1973 ◽  
Vol 73 (2) ◽  
pp. 351-359
Author(s):  
Brian Charlesworth ◽  
Deborah Charlesworth
Keyword(s):  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Allele Frequencies ◽  
The Other ◽  
Protein Polymorphism ◽  
Chromosome 3 ◽  
Laboratory Population ◽  
Selective Control

ABSTRACT This paper presents the results of a study of linkage disequilibrium between five polymorphic enzyme genes located on chromosome 3 of D. melamgaster. Three sets of chromosomes were examined: two represented samples from successive years of the same natural population, and one came from a large laboratory population. Out of the thirty possible tests for linkage disequilibrium between pairs of loci, two were significant at the 5% level and two at the 1% level. This result cannot reasonably be ascribed to chance alone. The pairs of loci that had a significant correlation in one sample had higher than average correlations in the other samples (though not necessarily in the same direction); this effect was highly significant statistically. There was no tendency for the high correlations to be associated with tightness of linkage between the loci concerned. All five loci were involved in at least one significant effect. It was concluded that these results are difficult to explain on the neutral allele theory of protein polymorphism, but are consistent with the concept of selective control of allele frequencies.

scholarly journals GENETIC VARIATION AND THE ECOLOGICAL PARAMETER "FOOD MEDIUM" IN CAGE POPULATIONS OF DROSOPHILA MELANOGASTER

1976 ◽  
Vol 18 (2) ◽  
pp. 379-383 ◽  
Author(s):  
S. Alahiotis
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Genetic Variants ◽  
Gene Pool ◽  
Ecological Factor ◽  
Common Gene ◽  
Enzyme Loci ◽  
Ecological Parameter ◽  
Food Medium

Impressive effects of the ecological factor "food medium" upon the frequencies of the lethal-bearing second chromosomes in Drosophila melanogaster were found in cage populations originated from a common gene pool. Allozyme frequencies for two second enzyme loci were also determined. The lethal frequencies found were higher when the environment was restrictive than when it was favorable. Moreover, the lethal frequencies were higher in populations of smaller size than in those of greater. The role of the lethal genetic variants in the structure of populations is discussed.

scholarly journals INDUCTION OF GENE POOL DIFFERENTIATION IN DROSOPHILA MELANOGASTER

1978 ◽  
Vol 20 (2) ◽  
pp. 265-273 ◽  
Author(s):  
S. Alahiotis ◽  
M. Pelecanos
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Differentiation ◽  
Environmental Factor ◽  
Gene Pool ◽  
Selective Effect ◽  
Ecological Parameter ◽  
Food Medium ◽  
Large Groups

The selective effect of the ecological parameter "food medium" upon the gene pool of Drosophila melanogaster was investigated in nine cage populations by estimating the allozyme frequencies of the a-Gpdh and Adh loci. The differentiation observed was found to depend dramatically upon the action of the above mentioned environmental factor. Small differences may be mainly attributed to the effect of the differing genetic backgrounds of each gene pool. When the environment was restrictive, a dramatic gene pool differentiation was observed. A discussion is provided bearing upon the observed induction of a process which involves large groups of coadapted genes upon which selection actually acts. Furthermore, the role of nutrition, and especially yeast, was found to have a profound effect upon the observed genetic differentiation of the gene pool of D. melanogaster.

Some comparative aspects of a longitudinal growth study in normal spanish children and other longitudinal studies

1986 ◽  
Vol 113 (4_Suppl) ◽  
pp. S93-S97 ◽  
Author(s):  
A. FERRANDEZ ◽  
E. MAYAYO ◽  
M. RODRIGUEZ ◽  
J.M. ARNAL ◽  
J. CARO ◽  
...  
Keyword(s):  
Longitudinal Studies ◽  
Environmental Conditions ◽  
Regional Differences ◽  
Longitudinal Growth ◽  
Growth Study ◽  
Growth Studies ◽  
Different Populations ◽  
Catch Up

Abstract The differences existing among some european longitudinal growth studies make it necessary to be cautious in the use of standards constructed on different populations. The improvement of the environmental conditions during the last 20 years is probably the most important cause of the "catch-up" phenomenon of the spanish stature. It is probable that racial characteristics also play a role, even in the same country as can be appreciated on comparing two spanish longitudinal studies based on children originary from different regions. All of wich indicates the need to use own standards in those countries wich, like ours, have lived through a period of intenses changes. Even exploratory studies of regional differences in the same country seem necesary.

scholarly journals Genetic Screens for Factors Involved in the Notum Bristle Loss of Interspecific Hybrids Between Drosophila melanogaster and D. simulans

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 269-282
Author(s):  
Toshiyuki Takano-Shimizu
Keyword(s):  
Drosophila Melanogaster ◽  
Interspecific Cross ◽  
Species Variation ◽  
Genetic Screens ◽  
Pure Species ◽  
Epistatic Interactions ◽  
X Chromosomes ◽  
Powerful Means ◽  
Different Populations ◽  
Deficiency Screening

Abstract Interspecific cross is a powerful means to uncover hidden within- and between-species variation in populations. One example is a bristle loss phenotype of hybrids between Drosophila melanogaster and D. simulans, although both the pure species have exactly the same pattern of bristle formation on the notum. There exists a large amount of genetic variability in the simulans populations with respect to the number of missing bristles in hybrids, and the variation is largely attributable to simulans X chromosomes. Using nine molecular markers, I screened the simulans X chromosome for genetic factors that were responsible for the differences between a pair of simulans lines with high (H) and low (L) missing bristle numbers. Together with duplication-rescue experiments, a single major quantitative locus was mapped to a 13F–14F region. Importantly, this region accounted for most of the differences between H and L lines in three other independent pairs, suggesting segregation of H and L alleles at the single locus in different populations. Moreover, a deficiency screening uncovered several regions with factors that potentially cause the hybrid bristle loss due to epistatic interactions with the other factors.

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.

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