Nonrandom association of genetic markers in a sample of South African blacks

According to classical genetic theory, allelic genes at one locus are expected to segregate and be manifested independently of allelic genes at another locus. At the population level any significant deviation from this general hypothesis resulting from specific biologic and genetic effects can be recognized in the form of nonrandom associations between genetic markers. The present data, consisting of 24 genetic polymorphisms determined from a sample of 998 unselected and unrelated South African blacks, offers an opportunity to test whether or not any such nonrandom associations exist between the genetic markers. After appropriate statistical calculations on the population data, we found that 13 pairs of genetic polymorphisms demonstrate a nonrandom association (statistically significant). Because the results cannot be explained in terms of known biologic mechanisms, we conclude that the associations observed could be due to random statistical effects (repeated application of the chi-square test) and/or to real (as yet unknown) biologic phenomena in the population studied. This tentative conclusion can serve as a guideline for more specific investigations.     

Leptospires in wildlife from Trinidad and Grenada

Serum samples from 894 wild animals (representing 31 species) from Trinidad and Grenada were examined by the microscopic agglutination test for leptospiral antibodies; 198 were positive. These included 39 bats, 88 mongooses, six opossums, 10 peridomestic rodents, 15 forest rodents, 10 lizards, and 30 toads. Thirteen pathogenic serogroups were involved. Thirty-nine Leptospira isolates were reported from mongooses, opossums, rodents and toads.     

A genetic study of immunoglobulin E

Path analysis gives evidence of genetic heritability (.425) for serum IgE levels. Complex segregation analysis indicates, in addition to significant polygenic heritability, a major regulatory locus RE, with homozygotes re/re maintaining persistently high levels of IgE. The gene frequency of re is .489, and the displacement is 1.67 standard deviations.     

A genetic study of Hirschsprung disease

Hirschsprung disease, or congenital aganglionic megacolon, is commonly assumed to be a sex-modified multifactorial trait. To test this hypothesis, complex segregation analysis was performed on data on 487 probands and their families. Demographic information on probands and the recurrence risk to relatives of probands are presented. An increased sex ratio (3.9 male:female) and an elevated risk to sibs (4%), as compared with the population incidence (0.02%), are observed, with the sex ratio decreasing and the recurrence risk to sibs increasing as the aganglionosis becomes more extensive. Down syndrome was found at an increased frequency among affected individuals but not among their unaffected sibs, and the increase was not associated with maternal age. Complex segregation analysis was performed on these family data. The families were classified into separate categories by extent of aganglionosis. For cases with aganglionosis beyond the sigmoid colon, the mode of inheritance is compatible with a dominant gene with incomplete penetrance, while for cases with aganglionosis extending no farther than the sigmoid colon, the inheritance pattern is equally likely to be either multifactorial or due to a recessive gene with very low penetrance. A model of gene action with random effects during morphogenesis is compatible with our observations.     

Microsatellite-aided detection of genetic redundancy improves management of the International Cocoa Genebank, Trinidad

Cacao (Theobroma cacao L.), the tree from which cocoa butter and chocolate is derived, is conserved in field genebanks. The largest of these ex situ collections in the public domain is the International Cocoa Genebank, Trinidad (ICG,T). Reduction of genetic redundancy is essential to improve the accuracy and efficiency of genebank management. This study examined the pedigree and genetic diversity in a subset of 387 accessions in this collection. Sibship reconstruction of this subset revealed 56 full-sib families nested within 189 half-sib families. Sixteen centers of interconnectivity were identified, which suggested a high level of genetic redundancy in the collection. Generally, consistent phylogenetic trees were obtained using different genetic distance measures. However, a principal coordinate analysis of the D _est differentiation measure elicited the best representation of accession group clustering, and we recommend this approach when probing fine-scale genetic differentiation among cacao accessions. The composite genetic diversity of 414 cacao accessions was contained in a core set of 59 unique accessions. These results have significant implications in the conservation of genetic resources of the ICG,T and other cacao genebanks. The approach developed in this study is recommended as a strategy to curators in guiding conservation management practices of cacao and other similar ex situ genebanks.     

A genetic study of syndactyly in Utah

Abstract

Pregnancy histories of 470 ever‐married women aged 40 years and older from three endogamous groups of marine fishermen of Puri, Orissa, are analyzed to estimate Crow's index of opportunity for selection. All these populations are migrants. The value of I ranges from 0.63 to 1.08. The results are interpreted in the light of their ethno‐historical, migratory backgrounds, degree of isolation, and population sizes. A comparison with published Indian data is also made.     

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.     

A molecular genetic study of natural strains of Saccharomyces isolated from Asturian cider fermentations

AIMS: To analyse the genetic diversity and the dynamics of Saccharomyces strains in spontaneous fermentation in ciders. The effect of the cellar, harvest and cider-making technology were evaluated. METHODS AND RESULTS: The ecology of spontaneous cider fermentations in the same cellar (Asturias) was studied for two consecutive harvests (2000 and 2001) by using mtDNA restriction analysis. Our results showed that there was a succession of genetically different strains of Saccharomyces during cider production. In general, strains of Saccharomyces bayanus species predominated at the early fermentation steps (begining and/or tumultuous fermentations), while Saccharomyces cerevisiae yeasts were the most abundant at the end of the fermentation. Five S. bayanus strains (patterns III, VII, VIII, XV and XVII) were present at significant frequencies in all the experimental tanks during the two consecutive years. The results of the cluster analysis (unweighted pair group method using average linkage) showed higher similarities for the patterns III, XV, VII and VIII. Therefore, these strains should be considered associated with the microbiota of this cellar. CONCLUSIONS: A high polymorphism within populations of Saccharomyces was found throughout the different stages of Asturian production of cider. In all the cider fermentations, a variable number of S. bayanus and S. cerevisiae strains was always present. Our results indicate, over the period of time studied, the existence of the natural microbiota in the cellar. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has allowed us to gain a better understanding of the role of wild Saccharomyces yeast in Asturian cider fermentations.