GENIC VARIATION IN MALE HAPLOIDS UNDER DETERMINISTIC SELECTION

ABSTRACT Genic variation in male haploids and male diploids was compared assuming constant fitnesses (derived from computer-generated random numbers) and infinite population size. Several models were studied, differing by the fitness correlation between the sexes (rs) and genotypes (rg), and by the intensity of selection as measured by the coefficient of variation (CV) of the fitness distribution. Genic variation was quantified using the proportion of polymorphic loci, P, the gene diversity at polymorphic loci, Hp, and the gene diversity over all loci, Ha. The two genetic systems were compared via variation ratios: variation in male haploidy/variation in male diploidy.—P and Ha were markedly lower for male-haploids than for male diploids, the variation ratios declining with increasing rs, rg and CV, but the two genetic systems were similar for Hp. Except for male diploids with rs = 1, the two sexes had different equilibrium gene frequencies but the sample sizes required to detect such differences reliably were larger than usually possible in surveys of natural populations.—Data from natural populations fit the above trends qualitatively, but the variation ratios are much lower than those from our analyses, except that for Hp, which is higher when Drosophila is excluded. Also, the frequency distribution of most common alleles from electrophoretic data has a deficiency of intermediate frequencies compared to that from the computer-generated sets of fitnesses, possibly reflecting either the influence of stochastic processes shifting frequencies away from equilibrium or the involvement of alleles under selection-mutation balance.——While electrophoretic data suggest that Drosophila has unusually high levels of genic variation, unusually low levels of genic variation in male haploids compared with male diploids are not strongly indicated. However, if further data confirm male haploids as having low levels of genic variation, likely explanations are that the bulk of electrophoretically detected variation involves fixed-fitness balancing selection, selection-mutation balance involving slightly deleterious recessive alleles, new favorable male haploid alleles moving more rapidly to fixation than under male diploidy and thus carrying linked loci to fixation faster, or some combination of these possible factors.

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GENIC HETEROGENEITY WITHIN ELECTROPHORETIC "ALLELES" AND THE PATTERN OF VARIATION AMONG LOCI IN DROSOPHILA PSEUDOOBSCURA

Genetics ◽

10.1093/genetics/93.4.997 ◽

1979 ◽

Vol 93 (4) ◽

pp. 997-1018

Author(s):

Rama S Singh

Keyword(s):

Balancing Selection ◽

Natural Populations ◽

Aldehyde Oxidase ◽

Xanthine Dehydrogenase ◽

Drosophila Pseudoobscura ◽

Mainland Population ◽

Polymorphic Loci ◽

Genic Variation ◽

Pattern Of Variation

ABSTRACT An investigation, similar to our previously reported xanthine dehydrogenase study, was undertaken to examine the extent of hidden genic variation at nine loci (five larval proteins, three esterases and one aldehyde oxidase) by sequential application of various electrophoretic criteria employing pH, gel concentration and buffer variation. Polymorphic loci appear to fall into two distinct groups: weakly polymorphic, including larval protein 6, 7, 8, 10 and 13 and esterase-1 and -6; and highly polymorphic, including esterase-5, Xdh and possibly Ao. Monomorphic loci may belong to a third group different from all polymorphic lori. Bogota, a geographical isolate that is reproductively isolated from the mainland population, was found to be genetically distinct at four of the ten loci examined in detail so far, including Xdh, whereas previously it was found to be genetically distinct at none. These results are discussed in the light of balancing selection, neutral and mutation-selection hypotheses of genic variation in natural populations.

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Enzyme variability in the Drosophila willistoni Group. V. Genic variation in natural populations of Drosophila equinoxialis

Genetics Research ◽

10.1017/s0016672300013562 ◽

1972 ◽

Vol 20 (1) ◽

pp. 19-42 ◽

Cited By ~ 44

Author(s):

Francisco J. Ayala ◽

Jeffrey R. Powell ◽

Martin L. Tracey

Keyword(s):

Genetic Variation ◽

Allelic Variation ◽

Natural Populations ◽

Starch Gel Electrophoresis ◽

Gene Frequencies ◽

Group V ◽

Neutral Genetic Variation ◽

Starch Gel ◽

Genic Variation ◽

Standard Techniques

SUMMARYWe have studied genetic variation at 27 loci in 42 samples from natural populations of a neotropical species, Drosophila equinoxialis, using standard techniques of starch-gel electrophoresis to detect allelic variation in genes coding for enzymes. There is considerarle genetic variability in D. equinoxialis. We have found allelic variation in each of the 27 loci, although not in every population. On the average, 71% of the loci are polymorphic – that is, the most common allele has a frequency no greater than 0·95 – in a given population. An individual is heterozygous on the average at 21·8% of its loci.The amount of genetic variation fluctuates widely from locus to locus. At the Mdh-2 locus arout 1% of the individuals are heterozygotes; at the other extreme more than 56% of the individuals are heterozygous at the Est-3. At any given locus the configuration of allelic frequencies is strikingly similar from locality to locality. At each and every locus the same allele is generally the most common throughout the distribution of the species. Yet differences in gene frequencies occur between localities. The pattern of genetic variation is incompatible with the hypothesis that the variation is adaptively neutral. Genetic variation in D. equinoxialis is maintained by balancing natural selection.The amount and pattern of genetic variation is similar in D. equinoxialis and its sibling species, D. willistoni. Yet the two species are genetically very different. Different sets of alleles occur at nearly 40% of the loci.

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Segregation of allozyme loci in megagametophytes of Engelmann spruce and subalpine fir

Genome ◽

10.1139/g88-018 ◽

1988 ◽

Vol 30 (2) ◽

pp. 103-107 ◽

Cited By ~ 1

Author(s):

Kathleen L. Shea

Keyword(s):

Natural Populations ◽

Segregation Ratio ◽

Colorado Front Range ◽

Abies Lasiocarpa ◽

Front Range ◽

Subalpine Fir ◽

Polymorphic Loci ◽

Engelmann Spruce ◽

Low Levels ◽

Allozyme Loci

Segregation ratios and linkage of 10 allozyme loci were examined in haploid megagametophytes obtained from natural populations of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in the Colorado Front Range. For data pooled over trees, the 1:1 segregation ratio expected at Mendelian loci was obtained for five polymorphic loci in 32 Engelmann spruce trees and for seven polymorphic loci in 40 subalpine fir trees. The Gdh and Idh loci in spruce were very tightly linked: no recombinants were detected among 60 megagametophytes of trees heterozygous for both loci. In fir only the Aco and Pgm-1 loci were linked, with an estimated recombination rate of 0.317 ± 0.073. The low levels of among-tree heterogeneity and of segregation distortion found in these populations suggest that reliable estimates of both genetic variation and outcrossing rates can be obtained using allozyme data from these wind-pollinated species.Key words: segregation, linkage, allozymes, Engelmann spruce, subalpine fir.

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Estimation of gene diversity at the b locus of the constant region of the immunoglobulin light chain in natural populations of European rabbit (Oryctolagus cuniculus) in Portugal, Andalusia and on the Azorean Islands.

Genetics ◽

10.1093/genetics/127.4.789 ◽

1991 ◽

Vol 127 (4) ◽

pp. 789-799 ◽

Cited By ~ 1

Author(s):

W van der Loo ◽

N Ferrand ◽

R C Soriguer

Keyword(s):

Light Chain ◽

Balancing Selection ◽

Gene Diversity ◽

Natural Populations ◽

European Rabbit ◽

Distribution Area ◽

Constant Region ◽

Immunoglobulin Light Chain ◽

B Locus ◽

Domestic Rabbits

Abstract The minimal gene diversity at a locus of the antibody constant region, as estimated in natural populations of rabbit, revealed levels of heterozygosity similar to those reported for the major histocompatibility complex in human and murine populations. Sera of 416 wild rabbits were collected on the Iberian peninsula and on three islands of the Azorean archipelago and analyzed for the occurrence of the serological markers of the b locus of the immunoglobulin light chain. All four serotypes present in domestic rabbits were found in Portugal. They represented less than 50% of the gene pool. In Andalusia this was less than 15% and on the Azorean islands less than 10%. The pronounced and systematic hierarchy in allele frequencies, previously found in populations from the more recent distribution area of the species, was not observed. On the peninsula, the frequencies of the "domestic" alleles were similar, averaging 10%. The Portuguese sample revealed a total heterozygosity of at least 87%. This high value was supported by at least 11 serologically different alleles, none of them occurring at frequencies above 20%. These data are in agreement with an Iberian origin of the European rabbit and strongly suggest the coalescence of b locus allelic lines drawn from Iberian and western populations. The role of balancing selection in the evolution of the b locus polymorphism was further emphasized.

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O equilíbrio de Hardy-Weinberg no sistema sanguíneo ABO: um estudo de caso em Engenheiro Coelho – SP

Ciência e Natura ◽

10.5902/2179460x43422 ◽

2021 ◽

Vol 43 ◽

pp. e16

Author(s):

Vinícius Freitas de Oliveira ◽

Guilherme Augusto Pianezzer ◽

Suzete Maria Silva Afonso

Keyword(s):

Random Mating ◽

Natural Populations ◽

Human Populations ◽

Gene Frequencies ◽

Weinberg Equilibrium ◽

Blood Types ◽

Infinite Population ◽

Hardy Weinberg Equilibrium ◽

And Migration

The genetics of human populations is the branch of Genetics that studies the dynamics of genes in natural populations, aiming at the elucidation of mechanisms that alter their genetic composition. Among the fundamentals of this science is the Hardy-Weinberg Equilibrium, which determines that gene frequencies remain unchanged and genotypic proportions reach a stable balance, obtaining the same constant relation with each other over time. To demonstrate this principle, it is necessary to admit that the studied population is not subject to evolutionary factors or to those that alter genotypic frequencies, increasing the homozygosity. More specifically, it is necessary to assume that the population obeys the following premises: random mating, infinite population, non-overlapping generations, in addition to the absence of mutation, selection and migration. More than recalling basic concepts of Genetics and Statistics, this article aims to describe the Bernstein Method for verifying the gene equilibrium for blood types. The research is concluded with a case study in the city of Engenheiro Coelho - SP, where the Hardy-Weinberg Equilibrium for blood types in the population is verified.

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ENZYME VARIABILITY IN NATURAL POPULATIONS OF DAPHNIA MAGNA III. GENOTYPIC FREQUENCIES IN INTERMITTENT POPULATIONS

Genetics ◽

10.1093/genetics/77.2.335 ◽

1974 ◽

Vol 77 (2) ◽

pp. 335-341

Author(s):

Paul D N Hebert

Keyword(s):

Daphnia Magna ◽

Annual Cycle ◽

Breeding System ◽

Natural Populations ◽

Genetic Effects ◽

Gene Frequencies ◽

Polymorphic Loci ◽

Genotype Frequencies ◽

Temporary Habitats ◽

Good Agreement

ABSTRACT In temporary habitats populations of the cyclical parthenogen, Daphnia magna, are re-established each year from sexual eggs and reproduce partheno-genetically for two or at most three generations. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in nineteen intermittent populations—Genotypic frequencies at polymorphic loci were ordinarily found to be in good agreement with Hardy-Weinberg proportions and disequilibria between loci were not observed. Although significant changes in gene frequencies were observed both during and between successive cycles, there was no evidence of the marked instability of genotype frequencies characteristic of permanent populations. The recombinational degradation of genotypes at the end of each annual cycle in temporaly habitats effectively prevents the genotypic structuring which develops when continued parthenogenesis is possible.

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A Comprehensive Study of Genic Variation in Natural Populations of Drosophila melanogaster. II. Estimates of Heterozygosity and Patterns of Geographic Differentiation

Genetics ◽

10.1093/genetics/117.2.255 ◽

1987 ◽

Vol 117 (2) ◽

pp. 255-271

Author(s):

Rama S Singh ◽

Lorenz R Rhomberg

Keyword(s):

Genetic Distance ◽

High Frequency ◽

Balancing Selection ◽

Geographic Distance ◽

Fixation Index ◽

Clinal Variation ◽

Lower Mode ◽

Polymorphic Loci ◽

Its Gene ◽

Genic Variation

ABSTRACT A study of genic variation in natural population of D. melanogaster was undertaken (1) to obtain a better estimate of heterozygosity by sampling a relatively large number of gene loci and (2) to identify different groups of polymorphic loci whose variation patterns might suggest different kinds of selection forces. A total of 117 gene loci (coding for 79 enzymes and 38 abundant proteins) were studied in 15 geographically distant populations originating from different continents. The findings of this study are as follows: (1) of the 117 gene loci studied, 61 are polymorphic and 56 are uniformly monomorphic everywhere. (2) An average population is polymorphic for 43% of its gene loci and an average individual is heterozygous for 10% of its gene loci. These estimates are remarkably similar among populations. (3) The average within-locality heterozygosity (HS) for polymorphic loci is uniformly distributed over the range of heterozygosity observed; i.e., given that a locus has any local variation, it is nearly as likely to have a lot as a little. (4) The distribution of FST (fixation index) is strongly skewed, with a prominent mode at 8–10% and a long tail of high values reaching a maximum of 58%. Two-thirds of all loci fall within the bell-shaped distribution centered on an FST of 8–10%, a result compatible with the notion that they are experiencing a common tendency toward small interlocality differences owing to extensive gene flow among populations. (5) The distribution of total heterozygosity (HT) has a prominent bimodal distribution. The lower mode consists of loci with single prominent allele and a few uncommon ones and the upper mode consists of clinally varying loci with a high FST(e.g., Adh and G6-pd), loci with many alleles in high frequency (e.g., Ao and Xdh) and loci with two alleles in high frequency in all populations but, with little interpopulational differentiation (e.g., Est-6 and α-Fuc). The loci in the lower mode are probably under purifying selection; a large proportion of those in the latter mode may be under balancing selection. (6) Comparison of genic variation for loci located inside vs. outside inversions, comparison of FST for inversions and their associated genes, and comparison of FST and map position for pairs of loci all suggest that, while linkage has some influence, it does not seem to constrain the pattern of variation that a locus may develop. (7) Eighteen polymorphic loci show latitudinal variation in allele frequencies which are consistent in populations from different continents. (8) Estimates of Nei genetic distance between population pairs are generally low between populations on the same continent and high between populations on different continents. There are two important exceptions: population pairs for which both localities are in the temperate zone show no relationship to distance, and in cases where both populations are tropical or subtropical, the genetic distance is higher than for the temperate-tropical comparisons and seem even higher than one would expect from the geographic distance separating them. The latter observation suggests that either geographic separation outweighs differences in environment in determining the genetic composition of a population or that all tropical populations are not experiencing the same environment.—The results are discussed in relation to the neutralist-selectionist controversy of genic variation and two important conclusions are drawn: First, there is a negative correlation between the number of loci sampled and the resulting heterozygosity. This means that available estimates of heterozygosity, 85% of which are based on 30 or fewer loci, are high and hence not appropriate for making between-taxa comparisons. Secondly, there is a group of loci, comprising one-third of polymorphic loci (or about 15% of all loci studied), that is distinguishable by different patterns of variation within and among populations. Most of these loci have clinal variation which is consistent with the hypothesis that their genetic variation is maintained by balancing selection.

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Molecular Characterization and Genetic Diversity Study in F3 Population of Rice

Progressive Agriculture ◽

10.3329/pa.v20i1-2.16839 ◽

2013 ◽

Vol 20 (1-2) ◽

pp. 1-8

Author(s):

MM Rahman ◽

L Rahman ◽

SN Begum ◽

F Nur

Keyword(s):

Genetic Distance ◽

Gene Diversity ◽

Random Amplified Polymorphic Dna ◽

Molecular Genetic ◽

Molecular Genetic Analysis ◽

Polymorphic Loci ◽

Rice Genotypes ◽

High Level ◽

Genetic Diversity Study ◽

Diversity Study

Random Amplified Polymorphic DNA (RAPD) assay was initiated for molecular genetic analysis among 13 F3 rice lines and their parents. Four out of 15 decamer random primers were used to amplify genomic DNA and the primers yielded a total of 41 RAPD markers of which 37 were considered as polymorphic with a mean of 9.25 bands per primer. The percentage of polymorphic loci was 90.24. The highest percentage of polymorphic loci (14.63) and gene diversity (0.0714) was observed in 05-6 F3 line and the lowest polymorphic loci (0.00) and gene diversity (0.00) was found in 05-12 and 05-15 F3 lines. So, relatively high level of genetic variation was found in 05-6 F3 line and it was genetically more diverse compared to others. The average co-efficient of gene differentiation (GST) and gene flow (Nm) values across all the loci were 0.8689 and 0.0755, respectively. The UPGMA dendrogram based on the Neis genetic distance differentiated the rice genotypes into two main clusters: PNR-519, 05-19, 05-14, 05-12 and 05-17 grouped in cluster 1. On the other hand, Baradhan, 05-9, 05-13, 05-11, 05-5, 05-6, 05-1, 05-4, 05-15 and 05-25 were grouped in cluster 2. The highest genetic distance (0.586) was found between 05-4 and 05-17 F3 lines and they remain in different cluster.DOI: http://dx.doi.org/10.3329/pa.v20i1-2.16839 Progress. Agric. 20(1 & 2): 1 8, 2009

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Variance analysis of immunoglobulin alleles in natural populations of rabbit (Oryctolagus cuniculus): the extensive interallelic divergence at the b locus could be the outcome of overdominance-type selection.

Genetics ◽

10.1093/genetics/135.1.171 ◽

1993 ◽

Vol 135 (1) ◽

pp. 171-187 ◽

Cited By ~ 1

Author(s):

W van der Loo

Keyword(s):

Heavy Chain ◽

Light Chain ◽

Gene Diversity ◽

Natural Populations ◽

Constant Region ◽

Immunoglobulin Light Chain ◽

Evolutionary Patterns ◽

B Locus ◽

Type Selection ◽

Predominant Allele

Abstract Population genetic data are presented which should contribute to evaluation of the hypothesis that the extraordinary evolutionary patterns observed at the b locus of the rabbit immunoglobulin light chain constant region can be the outcome of overdominance-type selection. The analysis of allele correlations in natural populations revealed an excess of heterozygotes of about 10% at the b locus while heterozygote excess was not observed at loci determining the immunoglobulin heavy chain. Data from the published literature, where homozygote advantage was suggested, were reevaluated and found in agreement with data here presented. Gene diversity was evenly distributed among populations and showed similarities with patterns reported for histocompatibility loci. Analysis of genotypic disequilibria revealed strong digenic associations between the leading alleles of heavy and light chain constant region loci in conjunction with trigenic disequilibria corresponding to a preferential association of b locus heterozygosity with the predominant allele of the heavy chain e locus. It is argued that this may indicate compensatory or nonadditive aspects of a putative heterozygosity enhancing mechanism, implying that effects at the light chain might be more pronounced in populations fixed for the heavy chain polymorphism.

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Intragenomic and intraspecific heterogeneity in rrs may surpass interspecific variability in a natural population of Veillonella

Microbiology ◽

10.1099/mic.0.038224-0 ◽

2010 ◽

Vol 156 (7) ◽

pp. 2080-2091 ◽

Cited By ~ 28

Author(s):

Anne-Laure Michon ◽

Fabien Aujoulat ◽

Laurent Roudière ◽

Olivier Soulier ◽

Isabelle Zorgniotti ◽

...

Keyword(s):

16S Rrna ◽

16S Rrna Gene ◽

Gene Diversity ◽

Natural Populations ◽

Variable Region ◽

Housekeeping Gene ◽

Single Copy ◽

Population Based ◽

Rrna Gene ◽

Gene Copies

As well as intraspecific heterogeneity, intragenomic heterogeneity between 16S rRNA gene copies has been described for a range of bacteria. Due to the wide use of 16S rRNA gene sequence analysis for taxonomy, identification and metagenomics, evaluating the extent of these heterogeneities in natural populations is an essential prerequisite. We investigated inter- and intragenomic 16S rRNA gene heterogeneity of the variable region V3 in a population of 149 clinical isolates of Veillonella spp. of human origin and in 13 type or reference Veillonella strains using PCR-temporal temperature gel electrophoresis (TTGE). 16S rRNA gene diversity was high in the studied population, as 45 different banding patterns were observed. Intragenomic heterogeneity was demonstrated for 110 (74 %) isolates and 8 (61.5 %) type or reference strains displaying two or three different gene copies. Polymorphic nucleotide positions accounted for 0.5–2.5 % of the sequence and were scattered in helices H16 and H17 of the rRNA molecule. Some of them changed the secondary structure of H17. Phylotaxonomic structure of the population based on the single-copy housekeeping gene rpoB was compared with TTGE patterns. The intragenomic V3 heterogeneity, as well as recombination events between strains or isolates of different rpoB clades, impaired the 16S rRNA-based identification for some Veillonella species. Such approaches should be conducted in other bacterial populations to optimize the interpretation of 16S rRNA gene sequences in taxonomy and/or diversity studies.

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