Gene Frequency Data Research Articles

GENETIC DIVERGENCE IN CLOSELY RELATED SIBLING SPECIES DROSOPHILA PSEUDOOBSCURA, DROSOPHILA PERSIMILIS AND DROSOPHILA MIRANDA.

Drosophila pseudoobscura, D. persimilis and D. miranda are three closely related sibling species. D. pseudoobscura is the most widespread species; the geographic distribution range of D. persimilis is included within that of D. pseudoobscura, while the distribution range of D. miranda is included within that of D. persimilis. D. pseudoobscura is found in a wide variety of environments, D. persimilis is restricted to cooler and moister habitats, and D. miranda prefers even cooler and more humid environments (Dobzhansky and Epling, 1944). D. pseudoobscura and D. persimilis differ from each other in the gene arrangements of the XL and the second chromosome. The Standard gene arrangement of the XR chromosome in D. pseudoobscura is found in the sex ratio XR chromosome of D. persimilis. The Standard XR chromosome of D. persimilis is not found in D. pseudoobscura. Both D. pseudoobscura and D. persimilis have extensive inversion polymorphism in the third chromosome, which is different in the two species except the Standard inversion which is found in both species (Dobzhansky and Epling, 1944). The chromosomes of D. miranda differ from the other two species by a large number of inversions (Dobzhansky, 1970). One of the autosomes of D. pseudoobscura is present only once in the chromosome group of D. miranda males; D. pseudoobscura is XX and XY in the female and the male respectively; D. miranda is X1X1X2X2 in the female and X'X2Y in the male (Dobzhansky, 1935). The Y chromosome of D. miranda has some regions which are homologous to X2 of D. miranda and the corresponding autosome of D. pseudoobscura (MacKnight, 1939). D. pseudoobscura, D. persimilis and D. miranda occur sympatrically in nature, they do not mate in nature, and in laboratory experiments strong sexual isolation is observed between them; D. miranda shows the strongest sexual isolation with the other two species. In the laboratory, D. pseudoobscura when crossed to D. persimilis produces sterile F1 males and fertile F1 females. Crosses of D. miranda with D. pseudoobscura or D. persimilis produce sterile hybrids of both sexes (Dobzhansky, 1970). Genetic variation at 43 different loci has been studied by electrophoresis of proteins and enzymes in several populations of D. pseudoobscura and D. persimilis (Prakash et al., 1969; Prakash, 1969; Prakash, 1977a; Prakash, 1977b). In this paper, the gene frequency data for these three species are presented. The data on D. miranda are reported here for the first time and the average gene frequency data for the other two species are presented for comparison.

Genetic differentiation in the colonising lizard Anolis grahami

Taylor and Gorman's (1975) gene frequency data from the Jamaican and Bermudan populations of Anolis grahami are reanalysed by using Fst statistics. Statistical drawbacks of the original analysis are indicated. The present analysis shows that the data are consistent with the theory of random genetic drift of selectively neutral mutations.

Gene diversity in Indian populations.

Gene frequency data of ten protein and enzyme loci in seven populations of India were collected from the literature. The gene differentiation among seven populations relative to total population was only 0.6%, indicating that the genic variation between populations was small compared to that within them. Using 29 common protein loci, the genetic distances between Indians and three major races of man, Caucasoids, Mongoloids, and Negroids were also determined. Indians are closer to Mongoloids than to Caucasoids or Negroids as indicated by the phylogenetic tree.

A collation of marker gene and dermatoglyphic diversity at various levels of population differentiation.

The use of dermatoglyphic traits to describe interpopulational diversity among human populations at various levels of differentiation is compared with similar analysis of gene frequency data by means of nonparametric methods employing distance matrices and dendrograms, and by a partition of total variability into its between and within population components. Congruence of dermatoglyphics and gene markers appears to vary with level of population differentiation -- the association remains insignificant until racial level of differentiation is considered. Different pitfalls of the data used are mentioned. The interpretation of these findings is discussed by comparison with other non-human studies.

Phosphoglucomutase Polymorphism in the Green Crab, Carcinus maenas

Starch-gel electrophoresis revealed a polymorphic system for the enzyme phosphoglucomutase (PGM) in muscle extracts of 100 green crabs, Carcinus maenas, sampled from Boothbay Harbor, Maine, in 1970 and 1971. This system comprised six phenotypes, including three homozygotes and the corresponding heterozygotes. Each phenotype consisted of two or more isozyme bands. The inheritance of the observed phenotypes can be explained by the existence of three allelic autosomal genes, PGMa, PGMb, and PGMc. The PGM isozymes of the green crab are described with gene frequency data from the population at Boothbay Harbor. These data conform to the Hardy–Weinberg distribution.

TESTING FOR SELECTIVE NEUTRALITY OF ELECTROPHORETICALLY DETECTABLE PROTEIN POLYMORPHISMS

The statistical assessment of gene-frequency data on protein polymorphisms in natural populations remains a contentious issue. Here we formulate a test of whether polymorphisms detected by electrophoresis are in accordance with the stepwise, or charge-state, model of mutation in finite populations in the absence of selection. First, estimates of the model parameters are derived by minimizing chi-square deviations of the observed frequencies of genotypes with alleles (0,1,2...) units apart from their theoretical expected values. Then the remaining deviation is tested under the null hypothesis of neutrality. The procedure was found to be conservative for false rejections in simulation data. We applied the test to Ayala and Tracey 's data on 27 allozymic loci in six populations of Drosophila willistoni . About one-quarter of polymorphic loci showed significant departure from the neutral theory predictions in virtually all populations. A further quarter showed significant departure in some populations. The remaining data showed an acceptable fit to the charge state model. A predominating mode of selection was selection against alleles associated with extreme electrophoretic mobilities. The advantageous properties and the difficulties of the procedure are discussed.

Infinite allele model with varying mutation rate.

Available data suggest that the variation in mutation rate among protein loci follows the gamma distribution. Thus, taking into account this variation, formulae are developed for the distribution of allele frequencies, mean and variance of heterozygosity, expected number of alleles, proportion of polymorphic loci, and genetic distance. These formulae should be more appropriate for the analysis of gene frequency data for protein loci than equivalent formulae with constant mutation rate.

Genetic variability in Chilean Indian populations and its association with geography, language, and culture.

Abstract Genetic variability among seven Chilean Indian populations (Aymara, Atacameno, Diaguita, Pehuenche, Mapuche, Alacaluf, and Yagan) is measured in terms of net codon differences per locus from gene frequency data on seven serologic markers. Indices of cultural and linguistic differences are computed surveying the various ethnographic accounts of these tribal populations. Of the variables, culture, language, geography, and the degree of Caucasoid admixture, only geography seems to be the important factor in explaining the variabilities in genetic distances among these populations. An empirical relationship between geographic distance and gene identity is also established and shown graphically.

Archeology, population genetics and studies of human racial ancestry.

Using traditional classification, many people have tried to determine the place and time of origin of the major human races. Two basically conflicting views have prevailed, one asserting that races developed as local variations in a species evolving phyletically over much of the Old World for up to one million years, and the other view holding that present races are local variations on populations recently expanding into most areas and replacing the previous hominid inhabitants, this occurring since the time of the Neanderthals. Both views are based on the same archeological data. Gene frequency data and time-calibrated genetic distance measures have recently been applied to this problem. Here we show that the probable demographic nature of Pleistocene populations has obscured genetic distances to such an extent that they cannot be used to discriminate between the two viewpoints of racial origins. The racial classifications themselves are probably not useful in this context and obscure the question, so that we presently do not have a scientifically valid understanding of racial origins.

Population genetic studies in kerala and the nilgiris (South West India).

A total of nearly 1,000 persons belonging to a number of caste, religious and tribal groupings in Kerala and the Nilgiri Hills of South India have been tested for genetic variation in 4 blood group, 5 serum protein and 17 enzyme systems as well as haemoglobin. The distribution of blood groups, serum protein and enzyme groups is similar to that reported for other South Indian populations. Abnormal haemoglobins were detected in several populations. Abnormal haemoglobins were detected in several populations, HbS being present in more than 20% of the Irula and Kurumba in the Nilgiri Hills. In the Kerala populations there were 4 examples of Hb AD and 1 of Hb AE. Genetic distance estimates using the gene frequency data indicate that the closest groups are the Nayar and Izhava and the Brahmin and Nayar. The tribal populations are approximately twice as far from the Nayar as they are from the Izhava. The Todas of the Nilgiri Hills are somewhat closer to the Brahmin of Kerala than they are to the other tribal populations.

Genetic distance and gene diversity among linguistically different tribes of Mexican Indians.

Using gene frequency data for 14 genetic loci, genetic distances between 13 tribes of Mexican Indians belonging to 12 language groups were determined and a dendrogram was constructed. The genetic distance between tribes is correlated more with geographic proximity than with language affinity. The gene diversity (heterozygosity) of the total population was decomposed into the three components, i.e., the gene diversity between three main linguistic groups, the gene diversity between tribes within the main linguistic groups and the gene diversity within tribes. About 95% of the total gene diversity exists within tribes, the intergroup and intertribe components being only about 5%.

Blood group, serum protein and red cell enzyme polymorphisms in a population from the Seychelle Islands.

161 inhabitants of the Seychelle Islands have been examined for blood group, serum protein, and red cell enzyme polymorphisms. The gene frequency data obtained from this survey supports the anthropological view that the present-day Creole-speaking inhabitants of the Seychelle Islands result from a admixture of African and European stock.

Gene differentiation among caste and linguistic populations of India.

Surveying the literature, gene frequency data on 10∼18 protein loci were collected from six caste populations of north India as well as from two linguistically different populations (Marathis and Gujaratis) and two migrant populations (Parsis and Iranis) in west India. The average heterozygosity per locus of protein loci in all these populations is found to vary from 8 to 11%. The gene differences between individuals from different populations are only slightly higher than those between individuals from the same population. Only 1 % of the total gene diversity (heterozygosity) is attributable between populations.

Some genetic interrelationships in England and Wales. A methodological investigation.

Gene frequency data from 13 areas in England and Wales have been collected and analysed. Results for four genetic systems: ABO, Rhesus D, PTC and colour blindness were used. Edwards’ distance statisti

Gene differences between Caucasian, Negro, and Japanese populations.

The numbers of gene (codon) differences per locus between two randomly chosen genomes within and between Caucasian, Negro, and Japanese populations have been estimated from gene frequency data for protein loci. The estimated number of gene differences between individuals from different populations is only slightly greater than the number between individuals from the same population.

The genetic structure of a tribal population, the Yanomama Indians. V. Comparisons of a series of genetic networks.

SUMMARYThe model of Cavalli‐Sforza and Edwards was used to investigate the gentic relationships of thirty‐seven Yanomama villages. Using gene frequency data from eleven genetic systems (MNS, P, Rh, Duffy, Kidd, Diego, Lewis, haptoglobin, Ge, PGM, and acid phosphatase), three hierarchical levels of analysis were carried out. The first level involved in the construction of a gentic network, based on genetic distance between villages, for each of three historically defined clusters of villages. Upon comparing the results with ethnohistory there was shown to be a good agreement between the historical development of a cluster and its genetic network.At the second level of analysis a genetic network was constructed in similar fashion for nineteen villages of the Western Yanomama subgroup, including the three village clusters previously analysed. At this level the integrity of the village clusters was largely maintaine, exceptions being due to specific socio‐political events that resulted in changes of the composition of the village gene pool.The highest level resulted in the construction of a network for all thirty‐seven villages which showed three of the five geographically defined tribal subgroups as distinct entities. The result of these analyses indicate that the model of Cavalli‐Sforza and Edwards can under certain circimstances be used when the requirements of the midel arenot met, and furthermore that the rate of divergence of human populations may approach a steady state at the level of major tribal subgroupings.

Polymorphic Serum Esterases in Two Species of Freshwater Fishes

Two simple, genetically determined serum esterase polymorphisms, suited for population analysis, are described in two species of freshwater fishes, white bream (Abramis blicca B.) and ruff (Acerina cernua L.). In both instances the synthesis of the enzyme bands was found to be controlled by two allelic codominant genes, which also in both instances were kept in equilibrium. Gene frequency data are presented from one population of each species.

POLYMORPHISM IN THE ISOPODSPHAEROMA RUGICAUDA

The spatial variation of gene frequencies has been recorded in several polymorphic species, including Biston betularia (Kettlewell, 1958), Cepaea nemoralis (Lamotte, 1951, 1959; Cain and Sheppard, 1954), C. hortensis (Clarke, 1962), Littorina obtusata (Sacchi, 1961), Homo sapiens (Allison, 1955), Drosophila spp. (Dobzhansky, 1951), and Spaeroma serratum (Bocquet, Levi, and Teissier, 1951; Hoestlandt, various papers). In at least the first five species, there are indications of the reasons for the variation. In some species changes in gene frequencies have been recorded as well (see, for example, Sheppard, 1961, on Panaxia dominula; Dobzhansky, 1958; Clarke and Murray, 1962). The causes of spatial variation and changes in gene frequencies in natural populations are controversial, with more importance ascribed to selection (Cain and Sheppard, 1954; Fisher and Ford, 1947) or to random drift (Lamotte, 1959). As Wright (1948) has emphasized, however, these are not exclusive categories but may interact in certain circumstances. The purpose of this paper is to describe the genetics of the polymorphic isopod, Sphaeroma rugicauda Leach, and to consider some aspects of gene-frequency data from 46 British populations of the species which suggest that natural selection is responsible for differences between populations.

Polymorphism in the Isopod Sphaeroma rugicauda

The spatial variation of gene frequencies has been recorded in several polymorphic species, including Biston betularia (Kettlewell, 1958), Cepaea nemoralis (Lamotte, 1951, 1959; Cain and Sheppard, 1954), C. hortensis (Clarke, 1962), Littorina obtusata (Sacchi, 1961), Homo sapiens (Allison, 1955), Drosophila spp. (Dobzhansky, 1951), and Spaeroma serratum (Bocquet, Levi, and Teissier, 1951; Hoestlandt, various papers). In at least the first five species, there are indications of the reasons for the variation. In some species changes in gene frequencies have been recorded as well (see, for example, Sheppard, 1961, on Panaxia dominula; Dobzhansky, 1958; Clarke and Murray, 1962). The causes of spatial variation and changes in gene frequencies in natural populations are controversial, with more importance ascribed to selection (Cain and Sheppard, 1954; Fisher and Ford, 1947) or to random drift (Lamotte, 1959). As Wright (1948) has emphasized, however, these are not exclusive categories but may interact in certain circumstances. The purpose of this paper is to describe the genetics of the polymorphic isopod, Sphaeroma rugicauda Leach, and to consider some aspects of gene-frequency data from 46 British populations of the species which suggest that natural selection is responsible for differences between populations.

Haemoglobin polymorphism in fishes.

MERISTIC and morphometric characters have been the most commonly used traits in the investigation of races or sub-populations of fishes. The differences in such characters among various populations may be due to variation in genetic as well as environmental factors. However, the relative influence of these two factors is usually unknown1. Consequently, it would be advantageous to use gene-frequency data based on Mendelian characters, the expression of which may be considered not to be influenced by environmental variation.