Negative correlation between heterozygosity and potential fertility in the Eveny population of Iakutiia

The relationship between heterozygosity of 9 polymorphic loci and fertility of women surviving beyond the menopause was studied in the North-Siberian tribe Eveny. The number of pregnancies negatively correlated with the individual heterozygosity (r = -0.2913 + 0.1302, P less than 0.05). Drastic fertility reduction in heterozygous women was observed for G1M, ACP and HP loci.     

Reduced heterozygosity depresses sperm quality in wild rabbits, Oryctolagus cuniculus

When close relatives are forced to reproduce, the resulting offspring inherit above average homozygosity and reduced fitness. Biologists now recognize inbreeding depression in the wild, a phenomenon that will probably increase as natural populations become depleted and fragmented. Inbreeding depression is most commonly expressed as compromised fertility and embryogenesis, but actual mechanisms remain poorly understood, especially for wild populations. Here, we examine how reduced heterozygosity influences spermatozoal and gonadal traits in wild rabbits (Oryctolagus cuniculus) sampled across the United Kingdom. By using a suite of 29 microsatellite markers (analyzed to confirm representation of individual heterozygosity across our sample), we found a significant negative relationship between heterozygosity and the production of normal sperm; the relationship was significant both between (n = 12) and within (n = 91 [total males], 42 [island], 49 [mainland]) populations. Reduced heterozygosity was also associated with decreased testis size across males (n = 112), but no relationship was seen at the population level, suggesting environmental confounds. Our results show, for a wild mammal, that inbreeding is associated with decreased sperm quality, confirming suggestions of links between inbreeding and elevated sperm abnormalities in rare felids . These findings could explain why inbreeding depression so frequently arises via compromised fertility and embryogenesis .     

Population genetics study of differential fertility in humans (based on an example of habitual abortion). II. Distribution of genotypes and heterozygosity levels for a variety of biochemical markers

Hereditary variation of 21 blood proteins coded by 22 monomorphic and 9 polymorphic loci was compared in 171 couples and 120 women with repeated spontaneous abortions in anamnesis (experimental group) and 183 couples with normal fertility (control group). Significant elevation of frequency of rare protein electrophoretic variants, marked deviation in distribution of genotypes for polymorphic loci, alteration in observed heterozygosity level were not found in experimental group. Statistically significant decrease in average value of D index (D = (hobs-hexp)/hexp; hobs, hexp--observed and expected heterozygosity per locus) was found in women of experimental group.     

Allozyme variation of Cyclobalanopsis championii (Fagaceae), a narrowly distributed species in southern Taiwan

Allozyme genetic variability in five natural populations of Cyclobalanopsis championii (Fagaceae) in Taiwan was investigated using 12 loci from 9 enzyme systems. The average values of parameters describing within-population variation, expected heterozygosity (He = 0.151), the percentage of polymorphic loci per individual (P = 50%), the average number of alleles per locus (A = 1.7), effective number of alleles per locus (Ae = 1.25), and the average number of alleles per polymorphic loci (AP = 2.2) are comparable to those of other long-lived woody plants. The overall fixation index (Fis = 0.208) indicates a significant deficiency of heterozygotes at the population level. Allelic frequency deviation from Hardy-Weinberg equilibrium was found for different loci in different populations. An exact test for population differentiation using the Tools for Population Genetic Analyses program also indicates that allelic frequencies among populations are significantly different (P < .001). Among-population variation, Gst, accounted for 9.2% of the total heterozygosity. The population at Shouchia and the southernmost population Nanjenshan had higher inbreeding coefficients (0.177 and 0.153, respectively) than did the northern populations. Genetic drift is supported by the observations of the variance components of linkage disequilibrium and a large proportion of loci in Nanjenshan and Shouchia that show pairwise locus disequilibrium. We believe continuous genetic drift in the southern populations will increase genetic divergence among populations of C. championii in Taiwan. Significant correlation was found between elevation and expected heterozygosity. We therefore inferred that temperature is the most important ecological factor to influence the genetic diversity of C. championii.     

Genetic heterogeneity and population structure of Gond-related tribes in the Vidarbha region of Maharashtra.

Genetic heterogeneity in nine polymorphic loci is observed among Gond-related tribes in the Vidarbha region of Maharashtra. Pardhans, with their high ABO*A2 gene frequency (4.01%), low m gene frequency (57%), high P*1 gene frequency (42.7%), and high HbS trait (31.58%), differ significantly from other tribes. Per locus average heterozygosity among the studied tribes ranged from 36.24% to 40.37%, with Pardhans being more heterozygous. Analysis by FST and the empirical relationship between average allele frequencies and the ratio of within-gene to total gene diversity show that the tribes are isolated and that differentiation among them is at an early stage and approximately in conformity with expected differentiation under genetic drift. However, distances and principal components analysis reveal that Pardhans are far removed from the other tribes and from other central Dravidian tribes. Furthermore, of the various demographic parameters estimated, the high average heterozygosity in Pardhans is significantly correlated with mean marital distance (MMD), regression of MMD on wife's age, and effective population size. There is congruence between genetic and demographic data, showing that Pardhans are distinct. This conforms with Haimendorf's (1979) contention based on cultural traits that Pardhans are Gonds by historical accident and are later migrants to the Gond area from the north. The most significant and practical observation of the present study is that migration from an originally nontribal (Pardhan) to a tribal (Gond) area and admixture lead to severe disease course, differential selection pressure, and hence highly elevated HbS trait frequency.     

Analysis of heterozygosity levels at P1,TF, PGM1, ACP1, HP, GC, GLO, C3, and ESD loci in pulmonary tuberculosis patients with different treatment outcomes]

Heterozygosity at nine genetic loci (PI, TF, PGM1, ACP1, HP, GC, GLO1, C3, and ESD) was analyzed in pulmonary tuberculosis patients with good (group 1, N = 71) and poor (group 2, N = 35) response to treatment. The observed heterozygosities were compared with the expected values, which were calculated from allele frequencies in a control sample of healthy individuals (N = 328 with all but one locus and 78 with ESD) according to Hardy-Weinberg expectations. The analysis showed that the observed heterozygosities gl of patients significantly differed from the expected values hl in the case of four loci (GC, PI, C3, and ACP1). The observed heterozygosity was higher than expected in three cases (PI, C3, and ACP1) and lower then expected (GC) in one case. When data on each individual locus were compared using Fisher's exact test, both groups of patients proved to significantly differ (PF < 0.05) from the control group in the same four loci. No difference in observed heterozygosity was detected between the two groups of patients. The mean expected heterozygosity was h = 0.386 +/- 0.00674; the mean observed heterozygosity was g = 0.415 +/- 0.02 in group 1, g = 0.402 +/- 0.026 in group 2, and g = 0.371 +/- 0.00955 in the control group. The t test did not reveal a significant difference between the mean values of expected observed heterozygosities. Heterozygosity at individual loci, rather than mean heterozygosity, was proposed as an integral nonspecific indicator of the genetic control of a disease, because the former directly implicates individual marker loci in the development of a disorder, whereas effects of individual loci may eliminate each other when mean heterozygosity is computed. Based on the results obtained, a genetic control was assumed for the development of the tuberculosis process in the lungs.     

Colonization, genetic diversity, and evolution in the Swedish sand lizard, Lacerta agilis (Reptilia, Squamata)

The Swedish sand lizard ( Lacerta agilis ) is a relict species from the post-glacial warmth period. From the geological history of this region, and more recent data on population fragmentation due to disturbance by man, it can be surmised that the Swedish sand lizards passed through at least one population bottleneck in relatively recent times. We tested this hypothesis by investigating the amount and structuring of genetic variability in six microsatellite loci in ten lizard populations from different parts of Sweden. We contrasted these data against those from a Hungarian population which we have reason to assume strongly resembles the founder population for Swedish sand lizards. The average number of alleles per locus in Sweden was 3.3, and these alleles were common in almost all populations, whereas the average number of alleles in the Hungarian population was 8.0. Likewise, the level of expected heterozygosity was lower in the Swedish populations (0.45) compared to the Hungarian population (0.70). The lower variability in Swedish populations is probably a consequence of a common population bottleneck during the immigration subsequent to the latest glacial period. The remaining variability is strongly subdivided between populations (F_ST=0.30) with the main genetic differences being between rather than within populations. Despite the marked isolation of the populations and the present small population sizes (N= 10–300 adults), the Swedish relict populations show a surprisingly high level of observed heterozygosity, indicating that small population size is probably a recent phenomenon.     

Individual fertility rate among minor tribal populations from Andhra Pradesh,India

Abstract

The Individual Fertility Rate (IFR), a measure of current fertility status in small and illiterate preindustrial societies, is estimated for five tribal populations from Andhra Pradesh, India. The Andhra tribes exhibit high individual fertility rates ranging between 49.62 ± 1.76 (Konda Dora) and 66.63 ± 3.16 (Manzai Mali) and fall in the high‐fertility category. The differences in IFR values between affinal and consanguineous couples are not significant. A direct positive relation between IFR and tribal hierarchy is observed with relatively higher IFR values recorded for socially higher‐ranked tribes in an ascending order from lower‐ to higher‐ranked groups.     

The heterozygosity for the biochemical and immunological markers of genes and the variability of morphophysiological traits in man

The relationship between heterozygosity of 9 biochemical and 5 blood group loci and variability of body length and age of menarche were studied in 467 women and 336 men from Moscow population. High and low levels of individual heterozygosity were shown in men to be associated with the maximal values of the coefficient of variation (CV) of body length, while in women strong positive correlation between the CV of body length and individual heterozygosity was demonstrated. The highest level of heterozygosity was revealed in medium-height men and low-height women. Highly heterozygous women were characterized either by early or by late age of menarche; early onset of menarche causes growth retardation. Positive correlation between the CV of body length and heterozygosity in women is due to the accumulation of low-height individuals having early age of menarche. The results are discussed in terms of Lerner's concept of genetic homeostasis. It is concluded that an average level of heterozygosity is optimal for a population.     

Protein polymorphism and genetic divergence in slow loris (genusNycticebus)

In this study, protein electrophoresis was assayed to detect genetic variation in GenusNycticebus. A total of 29 samples (2N. coucang and 27N. pygmaeus) were analyzed for 42 genetic loci. In the 27 samples ofN. pygmaeus, 4 loci were observed to be polymerphic. Therefore, the estimatedP value (proportion of polymorphic loci) is 0.095, theA value (average number of alleles each locus) is 1.045, and theH value (mean individual heterozygosity) is 0.040. After comparing theH ofN. pygmaeus with those of other primates reported, we found that the protein variation inN. pygmaeus is slightly lower than the average level. Additionally, we also observed obivious allele difference betweenN. pygmaeus andN. coucang. There are no shared alleles between these two species in eight loci. TheNei's genetic distance between them was calculated as 0.2541, which falls in the spectrum of genetic difference between species in primates.     

Analysis of the enzyme polymorphism in a plaice, Pleuronectes platessa L., population from the north-west coast of Brittany, France

A study of enzyme polymorphism by electrophoretical techniques permitted the genetic structure and the homogeneity degree of the plaice population present in the Abers Wrac'h and Benoit along the north-west coast of Brittany to be determined. Thirteen enzymic systems encoded by 21 loci were analysed and nine of these loci were polymorphic at the 5% level. The comparison of allelic frequencies and of observed heterozygosity h _obs did not show significant differences between these two individual groups. Nei's genetic identity ( I = 0.998) and distance ( D = 0.002) as estimated from allelic frequencies showed that the plaice of the two estuaries are very similar.
Thus, the plaice of A. Wrac'h and of A. Benoit belong to the same population in which the average level of polymorphism per locus P is 47% and the observed average heterozygosity per individual H _obs is 0.163 ± 0.094.     

Average allozyme heterozygosity in vertebrates correlates with Ka/Ks measured in the human-mouse lineage

It is well established that different allozyme proteins vary in heterozygosity in averages made over large numbers of species. For example, the enzyme 6-phosphogluconate dehydrogenase has a much higher average heterozygosity than glutamate dehydrogenase. Allozyme data alone provide insufficient power to determine the evolutionary cause of such a difference. Many studies have now been carried out on the DNA sequences coding for allozymes. These have identified diverse selective and nonselective causes of polymorphisms at individual loci. However the studies are mainly in a small number of model species; thus, it is difficult to identify from these DNA studies specific causes of global average heterozygosity differences among allozyme proteins. Here we demonstrate that estimates of average heterozygosity for 37 allozyme proteins in vertebrates correlate positively with Ka and Ka/Ks but not with Ks, measured in the human-mouse lineage. The values of Ka/Ks are less than 0.25, and Ka/Ks is negatively correlated with subunit number (quaternary structure), a measure of structural constraint. Proteins with lower levels of constraint have higher values of both Ka/Ks and heterozygosity. These results better support the hypothesis that differences in average allozyme diversity between proteins are more closely related to differences in the level of purifying selection than to differences in the underlying mutation rate or level of positive selection.     

Population genetics study of differential fertility in humans (based on an example of habitual abortion). III. Distribution of individual heterozygosity and genotype combinations for 9 polymorphic loci

Distribution of individual heterozygosity (the number of heterozygous loci per individual), wife/husband genetical differences and frequencies of genotypes formed by paired combination of eight polymorphic loci were studied in a group of couples and single women with repeated spontaneous abortions, and in a group of couples with normal fertility. No statistically significant differences were found for the first two parameters. Marked increase of genetical variability was shown for the women with repeated spontaneous abortions, as consequence of elevation of frequency of rare genotypic paired combinations. Therefore, differential fertility, as a component of stabilizing selection, alters the distribution of complex genotypes in human 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%.     

Population genetics of forest trees: Implications for the application of in vitro techniques

Summary Differences between forest trees and other organisms include higher DNA levels, higher levels of heterozygosity per individual, a greater proportion of polymorphic loci, a higher average number of alleles per loci, and generally lower levels of population structuring. Forest management practices are generally less intensive than those commonly applied to domesticated crop plants. Because of this and the long generation time and infrequent harvest schedule, the elements of risk are greater than for other domesticated plant species. Appropriate strategies for implementing in vitro techniques that take these differences into account are discussed.     

RAPD analysis of genetic diversity and population structure of Elymus sibiricus (Poaceae) native to the southeastern Qinghai-Tibet Plateau, China

Genetic diversity of Elymus sibiricus (Poaceae) was examined in eight populations from the southeast Qinghai-Tibet Plateau. We detected 291 RAPD polymorphic loci in 93 samples. The percentage of polymorphic bands (PPB) was 79%. Genetic diversity (H(E)) was 0.264, effective number of alleles (N(E)) was 1.444, Shannon's information index (H(O)) was 0.398, and expected Bayesian heterozygosity (H(B)) was 0.371. At the population level, PPB = 51%, N(E) = 1.306, H(E) = 0.176, I = 0.263, and H(B) = 0.247. A high level of genetic differentiation was detected based on Nei's genetic diversity analysis (G(ST) = 32.0%), Shannon's index analysis (33.7%), and the Bayesian method (θ(B) = 33.5%). The partitioning of molecular variance by AMOVA demonstrated significant genetic differentiation within populations (60%) and among populations (40%). The average number of individuals exchanged between populations per generation (N(m)) was 1.06. The populations were found to share high levels of genetic identity. No significant correlation was found between geographic distance and pairwise genetic distance (r = 0.7539, P = 0.9996). Correlation analysis revealed a significant correlation (r = 0.762) between RAPD H(E) found in this study and ISSR H(E) values from a previous study.     

Population genetic study of differential fertility in man (illustrated by habitual abortion). V. Distribution of individual heterozygosity and parameters of genotypic variability for a set of immunological genetic markers

Distribution of individual heterozygosity (the number of heterozygous loci per individual), frequencies of genotypes formed by paired combinations of 5 loci and values of linkage disequilibrium between 6 blood group loci were studied both in a group of couples and single women with recurrent abortions in anamnesis, and in a group of couples and single women with normal fertility. Statistically significant deficit of highly heterozygous individuals was found in the experimental group. Marked increase of genetical variability was shown for the women with repeated abortions, as a consequence of elevation of rare genotypic paired combination frequency. Therefore, differential fertility as a component of stabilizing selection alters the distribution of complex genotypes in human populations. Differences in values of linkage disequilibrium between women with repeated abortions and those of normal fertility were not found.     

Molecular cytogenetic study on the plants of Elymus nutans with varying fertility on the Qinghai-Tibet Plateau

A molecular cytogenetic investigation was conducted on plants of the allohexaploid species Elymus nutans with varying fertility on the Qinghai-Tibet Plateau. Molecular karyotyping revealed that chromosome variants were distributed unevenly among genomes and among different homologue chromosomes in each genome. The plants with varying fertility exhibited significantly higher numbers of chromosome variants than did the normal fertility samples, although both kinds of plants showed the same pattern of high-to-low polymorphism from the Y to St and H genomes. Heterozygosis and karyotype heterozygosity in the plants with varying fertility were 3- and 13-fold higher than those in normal samples, respectively. Significant negative correlations were found not only between seed setting rates and total genome heterozygosity but also between seed setting rates and heterozygosity of each genome in the plants of varying fertility. Chromosome pairing analysis was performed using genomic in situ hybridization in selected plants of different fertility levels. The pairing of chromosomes at meiotic metaphase I was mostly bivalent, although univalent, trivalent, quadrivalent, and other polyvalents also occurred; in addition, chromosome configuration forms and frequencies varied among the studied samples. ANOVA results showed that the average number of ring bivalents in the Y genome was significantly higher than those in the St and H genomes. Significant positive correlations between pollen grain fertility and ring bivalent number were found in the St and H genomes but not in the Y genome. Furthermore, chromosome configuration parameters (total bivalents, numbers of ring and rod bivalents) were found to be significantly correlated with heterozygosity and seed setting rates in the St and H genomes, respectively, but not in the Y genome. It was inferred that the seed setting rate and pollen grain fertility in E. nutans are strongly influenced by the heterozygosity of each genome, but the Y genome differs from the St and H genomes due to chromosome pair alterations. The St and H genomes may contain more chromosome structural variations than the Y genome in E. nutans.     

Correlations between heterozygosity and reproductive success in the blue tit (Cyanistes caeruleus): an analysis of inbreeding and single locus effects

To understand the mechanisms behind heterozygosity-fitness correlations (HFC), it is necessary to employ large numbers of markers with known function and independently estimate the variation in inbreeding in the population. Here we genotyped 794 blue tits with 79 microsatellites that were distributed across 25 chromosomes and that were classified either as "functional" (N= 58) or "neutral" (N= 21). We found a positive effect of individual heterozygosity at multiple loci on clutch size, on the number of eggs sired by males, and on the number of recruits produced by males and females. We documented the occurrence of some consanguineous matings and found evidence for a particular type of population structure that can contribute to the occurrence of inbreeding. As the set of "neutral" loci provided more power to detect HFC and identity disequilibrium, we argue that "neutral" markers are better predictors of the effects of inbreeding. The number of significant effects at single loci did not exceed the expected number of false positives and no strong effects were associated with heterozygosity at "functional" markers. Thus, the HFC found here cannot be attributed to strong effects of the loci under study.     

Genetic variation of Avicennia marina (Forsk.) Vierh. (Avicenniaceae) in Vietnam revealed by microsatellite and AFLP markers

Genetic variation of Avicennia marina in the costal area of Vietnam was examined using microsatellite and AFLP markers. By using five microsatellite loci a total of 21 alleles were detected. The average number of alleles per locus per population ranged from 1.667 to 3.000. The observed heterozygosity varied from 0.180 to 0.263, with an average of 0.210 indicating relatively low level of genetic variation comparing to the previous studies on A. marina in the worldwide range. The expected heterozygosity was larger than the observed heterozygosity leading to positive inbreeding coefficients in all the six populations. Highly significant departures from Hardy-Weinberg Equilibrium were detected in four populations. AFLP analysis revealed a total of 386 loci, of which 232 (60.1%) were polymorphic. In congruent with microsatellite markers relatively low levels of genetic variation were detected at both gene and nucleotide levels (H = 0.086; pi = 0.0054). Reduced level of genetic variation was found in the central population, and in the southern populations. Both microsatellite and AFLP markers revealed large genetic differentiation (F(ST) = 0.262 and 0.338, respectively) indicating strong genetic structure among regional populations. Pairwise genetic distance by AFLP showed two populations in the north and the other two in the south are closely related each other.