Biomedical subjects

J Mountain

Publications and source records attributed to J Mountain.

12 recordsLinked to original sources

PubMed2000

Distinguishing recombination and intragenic gene conversion by linkage disequilibrium patterns.

Deterministic theory suggests that reciprocal recombination and intragenic, interallelic conversion have different effects on the linkage disequilibrium between a pair of genetic markers. Under a model of reciprocal recombination, the decay rate of linkage disequilibrium depends on the distance between the two markers, while under conversion the decay rate is independent of this distance, provided that conversion tracts are short. A population genetic three-locus model provides a function Q of two-locus linkage disequilibria. Viewed as a random variable, Q is the basis for a test of the relative impact of conversion and recombination. This test requires haplotype frequency data of a sufficiently variable three-locus system. One of the few examples currently available is data from the Human Leukocyte Antigen (HLA) class I genes of three Amerindian populations. We find that conversion may have played a dominant role in shaping haplotype patterns over short stretches of DNA, whereas reciprocal recombination may have played a greater role over longer stretches of DNA. However, in order to draw firm conclusions more independent data are necessary.

Gene Conversion↗

PubMed1999

Global sequence diversity of BRCA2: analysis of 71 breast cancer families and 95 control individuals of worldwide populations.

The aim of this study was to evaluate the prevalence of simple sequence variation in the BRCA2 gene. To this end, 71 breast and breast-ovarian cancer (HBC/HBOC) families along with 95 control individuals from a wide range of ethnicities were analyzed by means of denaturing high-performance liquid chromatography (DHPLC) and direct sequence analysis. In the coding (10 257 bp) and non-coding (2799 bp) sequences of BRCA2, 82 sequence variants were identified. Three different, apparently disease-associated BRCA2 mutations were found in six HBC/HBOC families (8%): two splice site mutations in introns 5 and 21, and one frameshift mutation in exon 11. In the coding region, 53 simple sequence variants were found: 35 missense mutations, one 2 bp deletion (CT) resulting in a stop at codon 3364, one nonsense mutation with a stop at codon 3326, one deletion of a complete codon (AAA) resulting in the loss of leucine, and 15 silent mutations. In the non-coding region, 26 polymorphisms were detected. Of the 79 sequence variants that were not obviously disease-associated, eight were detected only in HBC/HBOC families. The remaining 71 variants were identified in both HBC/HBOC families and control individuals. Sixty three sequence variants (80%) were specific for a continent. Forty two percent (33 out of 79) of the sequence variants were detected exclusively in Africa, though only 13% of the 332 chromosomes screened were of African origin. Our data indicate that, in BRCA2, simple sequence variation is frequent [in the coding region 1 in 194 bp (straight theta = 2.2 x 10(-4)), and in the non-coding region 1 in 108 bp (straight theta = 4.4 x 10(-4)), respectively].

Africa↗

PubMed1997

The rough guide to electives overseas.

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Adaptation, Psychological↗

PubMed1995

Genetics and the origin of European languages.

A new set of European genetic data has been analyzed to dissect independent patterns of geographic variation. The most important cause of European genetic variation has been confirmed to correspond to the migration of Neolithic farmers from the area of origin of agriculture in the Middle East. The next most important component of genetic variation is apparently associated with a north-south gradient possibly due to adaptation to cold climates but also to the differentiation of the Uralic and the Indo-European language-speaking people; however, the relevant correlations are not significantly different from zero after elimination of the spatial autocorrelation. The third component is highly correlated with the infiltration of the Yamna ("Kurgan") people, nomadic pastoralists who domesticated the horse and who have been claimed to have spread Indo-European languages to Europe; this association, which is statistically significant even when taking spatial autocorrelations into account, does not completely exclude the hypothesis of Indo-European as the language of Neolithic farmers. It is possible that both expansions were responsible for the spread of different subfamilies of Indo-European languages, but our genetic data cannot resolve their relative importance.

Alleles↗

PubMed1989

Genetic and linguistic evolution.

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Biological Evolution↗

PubMed1988

Reconstruction of human evolution: bringing together genetic, archaeological, and linguistic data.

The genetic information for this work came from a very large collection of gene frequencies for "classical" (non-DNA) polymorphisms of the world aborigines. The data were grouped in 42 populations studied for 120 alleles. The reconstruction of human evolutionary history thus generated was checked with statistical techniques such as "boot-strapping". It changes some earlier conclusions and is in agreement with more recent ones, including published and unpublished DNA-marker results. The first split in the phylogenetic tree separates Africans from non-Africans, and the second separates two major clusters, one corresponding to Caucasoids, East Asians, Arctic populations, and American natives, and the other to Southeast Asians (mainland and insular), Pacific islanders, and New Guineans and Australians. Average genetic distances between the most important clusters are proportional to archaeological separation times. Linguistic families correspond to groups of populations with very few, easily understood overlaps, and their origin can be given a time frame. Linguistic superfamilies show remarkable correspondence with the two major clusters, indicating considerable parallelism between genetic and linguistic evolution. The latest step in language development may have been an important factor determining the rapid expansion that followed the appearance of modern humans and the demise of Neanderthals.

Archaeology↗

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