Genetic distance and gene diversity among ten endogamous groups in Chhattisgarh,Central India

A genetic survey has been conducted among the Rawats and Telis, two endogamous caste populations of Chhattisgarh, Central India. Using the gene frequency data for three genetic loci, genetic distance among ten population groups have been calculated. The gene differentiation among these population groups is only about 2 per cent.     

Isolation by distance, linguistic similarity, and the genetic structure on Bougainville Island

Previous research has revealed extensive genetic variation among villages on Bougainville, in the Solomon Islands. Using previously published gene frequency data for seven loci, the role of isolation by distance in structuring genetic variation on Bougainville was reanalyzed. Newer methods of kinship estimation show that earlier estimates of the isolation by distance parameters were low. The fit of the model is highly significant (R2 = 0.409; P less than 0.001), and the parameter estimates indicate high isolation: a = 0.0538, b = 0.1978, L = -0.0057. Several methods of residual analysis were applied in order to determine factors affecting the fit of the model. Linguistic similarity has a significant effect on genetic variation once the effects of geographic distance are taken into account. Population-specific deviations from the expected model may be explained, in part, in terms of population history. Compared to other human populations, Bougainville Island shows an even greater among-group variation than has been suggested previously.     

Relationship between genetic distance and heterosis for yield and morphological traits in winter canola (Brassica napus L.)

Genetic distance among canola cultivars was estimated through multivariate analysis. Thirty cultivars from various sources were analyzed and clustered based upon five morphological characteristics and yield components-crown diameter, number of branches plant^-1, number of pods plant^-1, number of seeds pod^-1 and yield plant^-1 -and placed in three distinct clusters. Two cultivars from each cluster were selected as parents and 15 partial-diallel inter- and intra-cluster crosses were made between the six selected parents and evaluated at two locations in Michigan in 1990/1991. The association between genetic distance and mid-parent heterosis was investigated. The correlation between genetic distance and heterosis was positive and highly significant for seed yield, number of pods plant^-1, and number of seeds pod^-1. Clustering, based on yield and yield-component traits, demonstrated that inter-cluster heterosis was greater than intra-cluster heterosis in the majority of cases.     

Relationship between heterozygosity and genetic distance in the three major races of man

In pairwise comparisons of gene frequency data from the three major races of man, the single locus measures of the heterozygosity within and the genetic distance between races are shown to be strongly correlated across the loci coding for red cell proteins and enzymes. The intercept of the regression line of genetic distance on heterozygosity in protein enzyme loci is statistically insignificant. These findings suggest that the genetic variability at the enzyme and protein loci in man is probably maintained by a balance of mutation and random genetic drift. At the blood group loci, however, the observed relationship between genetic distance and heterozygosity does not follow the expectation of the neutral mutation hypothesis. These observations are discussed in terms of the changes in probability of identical monomorphism in two populations during the process of gene differentiation.     

The St. Lawrence Island Eskimos: genetic variation and genetic distance

The Eskimos of St. Lawrence Island have been typed for genetic variation at 44 discrete genetic loci. Three private polymorphisms, at the 2,3-diphosphoglycerate mutase, peptidase B, and purine nucleoside phosphorylase loci, have been observed, which may be useful in future studies of genetic relationships between Eskimos and other circumpolar populations. Genetic distance analysis reveals a close relationship between the St. Lawrence Island Eskimos and other Eskimo populations and that the Eskimo populations form a distinct cluster from Amerindian populations. The St. Lawrence Island Eskimos appear to be more similar to Asiatic Eskimos than to other groups. Caucasian admixture in this population is estimated to be between 2 and 7%.     

Assessment of genetic diversity and relationship among a collection of US sweet sorghum germplasm by SSR markers

Sweet sorghum (Sorghum bicolor L.) is a type of cultivated sorghums and has been recognized widely as potential alternative source of bio-fuel because of its high fermentable sugar content in the stalk. A substantial variation of sugar content and related traits is known to exist in US sweet sorghum. The objectives of the study were to assess the genetic diversity and relationship among the US sweet sorghum cultivars and lines using SSR markers and to examine the genetic variability within sweet sorghum accessions for sugar content. Sixty-eight sweet sorghum and four grain sorghum cultivars and lines were genotyped with 41 SSR markers that generated 132 alleles with an average of 3.22 alleles per locus. Polymorphism information content (PIC) value, a measure of gene diversity, was 0.40 with a range of 0.03–0.87. The genetic similarity co-efficient was estimated based on the segregation of the 132 SSR alleles. Clustering analysis based on the genetic similarity (GS) grouped the 72 sorghum accessions into 10 distinct clusters. Grouping based on clustering analysis was in good agreement with available pedigree and genetic background information. The study has revealed the genetic relationship of cultivars with unknown parentage to those with known parentage. A number of diverse pairs of sweet sorghum accessions were identified which were polymorphic at many SSR loci and significantly different for sugar content as well. Information generated from this study can be used to select parents for hybrid development to maximize the sugar content and total biomass, and development of segregating populations to map genes controlling sugar content in sweet sorghum.     

Two complementary perspectives on inter-individual genetic distance

This paper examines population structure through the prism of pairwise genetic distances. Two complementary perspectives, framed as two simple questions, are explored: Q1: What is the probability that a random pair of individuals from the same local population is more genetically dissimilar than a random pair from two distinct populations? Q2: On average, how genetically different are two individuals from the same local population, in comparison with two individuals chosen from any two distinct populations? Models are developed to provide quantitative answers for the two questions, given allele frequencies across any number of markers from two diploid populations. The probability from Q1 is shown to drop to zero with increasing number of genetic markers even for very closely-related populations and rare alleles. The average genetic dissimilarity of two individuals from distinct populations diverges from the average dissimilarity of two individuals from the same population by a percentage dependent on estimates of population differentiation. This perspective also suggests a measure of population distance based on the intuitive notion of pairwise genetic distance, along with a simple method of estimation. Results from recent empirical research on inter-individual genetic distance in human populations are analyzed in the context of the theoretical framework.     

Mutant allele frequencies and genetic distance relationships in domestic cat populations of lower Egypt and the eastern Mediterranean

Summary Gene frequency surveys conducted in Alexandria and Cairo reveal genetic profiles which are extensions of those that characterize the cat populations of European cities. For nine selected comparisons with Alexandria, regression analysis indicates that a linear function best describes the relationship between Nei's and Cavalli-Sforza's genetic distance indices and geographic distance.     

The blacks of Panama: their genetic diversity as assessed by 15 inherited biochemical systems

Panama's black citizens are culturally and historically divisible into two groups, the Spanish-speaking coloniales and the English-speaking anglos or afro-antillanos. Until recently these groups have been geographically as well as culturally isolated one from the other, although both are predominantly of West and Southwest African origin. Assessment of the genetic diversity within-villages and within language groups reveals as much, possibly somewhat more, diversity in 15 inherited biochemical markers within villages and language groups as that which obtains between villages and language groups. A number of rare variants at the 6-phosphogluconate dehydrogenase, lactate dehydrogenase, and esterase D loci were encountered and are described.     

RFLP variation and genealogical distance,multivariate distance,heterosis, and genetic variance in oats

Patterns of restriction fragment length polymorphisms (RFLPs) have been proposed as estimators of genetic diversity among breeding lines and as predictors of heterosis and genetic variance. We evaluated these proposals by using a set of nine elite oat lines crossed in a diallel mating design without reciprocals. RFLP analysis was conducted using HindIII-digested DNA and a total of 107 probes from three different sources: 14 heterologous wheat cDNA clones, 17 oat genomic clones, and 76 oat cDNA clones. Of the 77 probes that produced high-quality autoradiographs, 26 detected polymorphisms among this set of lines, with an average of 2.6 variants per probe. RFLP-based genetic distance (FD) was calculated from these data by using Nei and Li's measure of genetic similarity, and was compared with two other measures of genetic divergence. Genealogical distance (GD ^*) was obtained from the coefficients of parentage based on known parental pedigrees, and multivariate distance (DI) was calculated by using the first five principal components of the parental correlation matrix for 12 agronomic traits. FD was significantly correlated with GD ^* (r=0.63, P<0.01), but not with DI (r=-0.05). Cluster analysis based on these three distance estimates did not produce equivalent groupings, but the FD and GD ^* clusters were more similar to each other than to the DI clusters. These results indicate that: (1) sufficient variation exists for further application of RFLP technologyto oats, (2) RFLPs could provide accurate estimates of genetic divergence among elite oat lines, and (3) it is unlikely that dispersed markers can predict heterosis or population genetic variance in oats. Further investigations will require more parental lines, a larger set of markers, and more information on the linkage relationships between RFLP markers and loci controlling the trait of interest.Journal paper No. J-15302 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011, USA. Project No. 2818 and 2447. Supported by Quaker Oats grant to M. Lee     

Genetic studies among the sedentes and migrant Oraons of eastern India

A total of 334 Oraons of both sexes from two localities in eastern India were tested for 11 polymorphic and six monomorphic blood genetic markers. The sample comprised 130 sedentes from the Gumla district in Bihar and 204 migrants to the Jalpaiguri district of North Bengal. At the hemoglobin locus one example of HbAS was observed in the Gumla sample, while two cases of HbAS were found in the Jalpaiguri group. The Oraons are a distinct tribe and are characterized by a very low frequency of Hp1, TFC2, and a high frequency of TfD1 and GcIF at the serum protein loci. In the red cell enzyme systems the Oraons have a higher frequency of pa at the acid phosphatase locus and GLO1 at the Glyoxalase I locus. Absence of red cell lactate dehydrogenase and very low HbS and GdB- is also characteristic of the Oraons. A probable new nondeficient slow variant of Gd has been observed in polymorphic frequency in the Oraons of Gumla. There was an excess of homozygotes at the Gc locus. No significant difference in the gene frequency between the two groups of Oraons was observed at any of the loci. Genetic distance estimates using the gene frequency data indicate that the Oraons of the two localities are genetically homogeneous and form one cluster with the Bhils. They are nearer to the Irula and Kurumba tribes of the Nilgiris rather than the other Dravidian tribes, Tamils, or Nayars.     

An anthropobiological study in Basse Kotto (Central Africa). I. Erythrocyte and sero-genetic markers: an analysis of the genetic differentiation

Phenotype and allele frequencies for hemoglobin types (Hb beta), acid phosphatase (AcP), phosphoglucomutase (PGM1 and PGM2), esterase D (EsD), 6-phosphogluconate dehydrogenase (6-PGD), glyoxalase I (GLO), superoxide dismutase (SOD A), and adenylate kinase (AK) as well as for haptoglobins (Hp), group-specific component (Gc), transferrin (Tf), Gm, and Inv groups and albumin, are reported in the Mbugu, Sango, Yakpa, and Baya Mandja ethnic groups in the Basse Kotto district of the Central African Republic. The total sample size amounts to 133 males and 128 females aged from 16 to 60, unrelated and healthy. A new albumin variant (albumin Mbugu) is described and discussed. The average heterozygosity is high in each group because of a high degree of exogamy. the FST average standardized value among the four groups indicates that the genetic differentiation in Basse Kotto is at level of about 2%. This indicates that the four examined groups might be considered genetically homogeneous, in spite of their different ethnic origins. The genetic distances among the four groups show that only the Baya Mandja are less closely related to the other three groups because of their foreign origin.     

A method to measure genetic distance between allogamous populations of alfalfa (Medicago sativa) using RAPD molecular markers

 Alfalfa (Medicago sativa L.) is a forage legume of world-wide importance whose both allogamous and autotetraploid nature maximizes the genetic diversity within natural and cultivated populations. This genetic diversity makes difficult the discrimination between two related populations. We analyzed this genetic diversity by screening DNA from individual plants of eight cultivated and natural populations of M. sativa and M.  falcata using the RAPD method. A high level of genetic variation was found within and between populations. Using five primers, 64 intense bands were scored as present or absent across all populations. Most of the loci were revealed to be highly polymorphic whereas very few population-specific polymorphisms were identified. From these observations, we adopted a method based on the Roger’s genetic distance between populations using the observed frequency of bands to discriminate populations pairwise. Except for one case, the between-population distances were all significantly different from zero. We have also determined the minimal number of bands and individuals required to test for the significance of between-population distances. Received: 7 July 1997 / Accepted: 28 October 1997     

Anthropometric variation among the reddis of Southern Andhra Pradesh,India

Five select Reddi populations based on 750 males in the age range of 20 to 50 years have been studied for 15 anthropometric measurements and 10 indices. The Pokanati show higher mean value for a majority of the measurements. F-values are significant for all measurements except for bicristal breadth. All indices but nasal index show negligible variation. Mesocephalic heads predominate among Pokanati and dolicocephalic heads among the rest. the cluster analysis and principal coordinate analysis, as diagrammatically represented, show the extent of variation among the five Reddi populations.     

同功酶电泳在种群遗传研究中的应用

本文扼要介绍了同功酶的分类和酶带的命名;介绍了利用酶带的相对频率求算种群间遗传相似系数和遗传距离;也介绍了利用遗传相似系数进行聚类分析的两种方法．     

新疆甜高粱种质资源遗传多样性的SSR分析

选用50对SSR引物对新疆现有72份甜高粱种质资源进行遗传多样性分析。结果表明:有20对引物在72份甜高粱种质资源中表现为多态性。共检测到91个等位基因,每对引物可检测到的等位基因数目为2～5个,平均为3.45个。多态性信息量(PIC)的变动范围为0.2859～0.6652,平均为0.5057。72份甜高粱种质间的遗传相似系数变化范围为0.2001～1.000,平均值为0.5599。UPGMA聚类分析将72份材料划分为A、B两大类群,A群包括69份材料,而A群又被分成从Ⅰ到Ⅺ共11个亚群,B群包括3份材料,农艺性状近似的大多被聚到同一类群。     

Genetic distance and species formation in evolving populations

Summary We compare the behavior of the genetic distance between individuals in evolving populations for three stochastic models.In the first model reproduction is asexual and the distribution of genetic distances reflects the genealogical tree of the population. This distribution fluctuates greatly in time, even for very large populations.In the second model reproduction is sexual with random mating allowed between any pair of individuals. In this case, the population becomes homogeneous and the genetic distance between pairs of individuals has small fluctuations which vanish in the limit of an infinitely large population.In the third model reproduction is still sexual but instead of random mating, mating only occurs between individuals which are genetically similar to each other. In that case, the population splits spontaneously into species which are in reproductive isolation from one another and one observes a steady state with a continual appearance and extinction of species in the population. We discuss this model in relation to the biological theory of speciation and isolating mechanisms.We also point out similarities between these three models of evolving populations and the theory of disordered systems in physics. Offprint requests to: P.G. Higgs     

Migration and genetic infrastructure of the Central American Guaymi and their affinities with other tribal groups

New genetic data on 40 red cell enzymes, antigenic blood groups, and serum proteins representing 42 separate loci, are reported for two Guaymi communities in Southeastern Costa Rica. These two settlements, Limoncito and Abrojo, are of recent origin, having been established by Panamanian migrants in the last 50 years. Detailed data on the provenance of these migrants permits an analysis of how these settlement patterns differ from those typical of less acculturated Amerindians from the lowlands of South America. The genetic compositions of these two communities are compared with those of previous Panamanian Guaymi samples, and several points are established: (1) One of the localities, Limoncito, contains families from both Guaymi dialect groups (eastern and western), and the allelic frequencies are intermediate between those of the dialect groups. (2) The other settlement, Abrojo, is quite similar to the western Guaymi, as expected from historical reconstruction of its antecedents. (3) In general, the degree of infratribal genetic diversity is less than that found in lowland South American tribes, and the difference may be due to a diffuse settlement pattern among the Guaymi. (4) The Guaymi are also compared genetically with other tribes in low Central America and northern South America, and appear to be similar to their immediate Chibcha neighbors to the east and west. The implications of a pair of "private polymorphisms" are discussed in the context of the time of dialectic and tribal divergence in this zone.     

Construction of phylogenetic profiles based on the genetic distance of hundreds of genomes

Phylogenetic profiles have been widely applied in functional genomics research, especially in the prediction of protein-protein interactions (PPIs). A key issue in phylogenetic profiling is how to effectively select reference organisms from the available hundreds of genomes. In this study, we performed an assessment of reference organism selection based on the genetic distance between the target organism and 167 reference organisms. We found that inclusion of reference organisms from all distance levels had better performance in the prediction of PPIs than that at each distance level. The PPI prediction reached an optimal level when 70% of the reference organisms at all distance levels were selected; and this performance was similar to that in the optimal condition based on the taxonomy tree in our previous study. Because measurement of genetic distance is direct and simple compared to the topology of the taxonomy tree, we suggest selecting reference organisms based on genetic distance in the construction of phylogenetic profiles.     

A twin study of dental dimension. II. Independent genetic determinants

To demonstrate the presence of independent genetic determinants of multiple correlated tooth dimensions from twin data, a multivariate analysis was performed on the covariance matrices of monozygotic and dizygotic within-pair differences for mesiodistal and buccolingual dimensions of 28 teeth of the secondary dentition. The results provided strong evidences that the correlation among tooth dimensions is primarily genetic in origin, probably attributable to the pleiotropic action of either independent genes or groups of genes. Among the genetic factors that were identified, one appeared to affect the maxillary teeth in general while a second influenced primarily the anterior mandibular teeth. There was a striking tendency for homologous measurements on the right and left sides to be associated with the same genetic factor. In contrast, genetic determination of the maxillary and mandibular dentition seemed to be independent of each other, and a wider range of genetic factors were found to influence the mandibular than the maxillary teeth, suggesting that a differential degree of evolutionary stability may have been achieved in the teeth of the two jaws.