Biomedical subjects

Gunter Weiss

Publications and source records attributed to Gunter Weiss.

3 recordsLinked to original sources

PubMed2003

Testing substitution models within a phylogenetic tree.

Phylogenetic tree reconstruction frequently assumes the homogeneity of the substitution process over the whole tree. To test this assumption statistically, we propose a test based on the sample covariance matrix of the set of substitution rate matrices estimated from pairwise sequence comparison. The sample covariance matrix is condensed into a one-dimensional test statistic Delta = sum ln(1 + delta(i)), where delta(i) are the eigenvalues of the sample covariance matrix. The test does not assume a specific mutational model. It analyses the variation in the estimated rate matrices. The distribution of this test statistic is determined by simulations based on the phylogeny estimated from the data. We study the power of the test under various scenarios and apply the test to X chromosome and mtDNA primate sequence data. Finally, we demonstrate how to include rate variation in the test.

Animals↗

PubMed2002

Reduced Y-chromosome, but not mitochondrial DNA, diversity in human populations from West New Guinea.

To investigate the paternal population history of New Guinea, 183 individuals from 11 regional populations of West New Guinea (WNG) and 131 individuals from Papua New Guinea (PNG) were analyzed at 26 binary markers and seven short-tandem-repeat loci from the nonrecombining part of the human Y chromosome and were compared with 14 populations of eastern and southeastern Asia, Polynesia, and Australia. Y-chromosomal diversity was low in WNG compared with PNG and with most other populations from Asia/Oceania; a single haplogroup (M-M4) accounts for 75% of WNG Y chromosomes, and many WNG populations have just one Y haplogroup. Four Y-chromosomal lineages (haplogroups M-M4, C-M208, C-M38, and K-M230) account for 94% of WNG Y chromosomes and 78% of all Melanesian Y chromosomes and were identified to have most likely arisen in Melanesia. Haplogroup C-M208, which in WNG is restricted to the Dani and Lani, two linguistically closely related populations from the central and western highlands of WNG, was identified as the major Polynesian Y-chromosome lineage. A network analysis of associated Y-chromosomal short-tandem-repeat haplotypes suggests two distinct population expansions involving C-M208--one in New Guinea and one in Polynesia. The observed low levels of Y-chromosome diversity in WNG contrast with high levels of mtDNA diversity reported for the same populations. This most likely reflects extreme patrilocality and/or biased male reproductive success (polygyny). Our data further provide evidence for primarily female-mediated gene flow within the highlands of New Guinea but primarily male-mediated gene flow between highland and lowland/coastal regions.

Chromosomes, Human, Y↗

PubMed2002

Ancient DNA analyses reveal high mitochondrial DNA sequence diversity and parallel morphological evolution of late pleistocene cave bears.

Cave bears (Ursus spelaeus) existed in Europe and western Asia until the end of the last glaciation some 10,000 years ago. To investigate the genetic diversity, population history, and relationship among different cave bear populations, we have determined mitochondrial DNA sequences from 12 cave bears that range in age from about 26,500 to at least 49,000 years and originate from nine caves. The samples include one individual from the type specimen population, as well as two small-sized high-Alpine bears. The results show that about 49,000 years ago, the mtDNA diversity among cave bears was about 1.8-fold lower than the current species-wide diversity of brown bears (Ursus arctos). However, the current brown bear mtDNA gene pool consists of three clades, and cave bear mtDNA diversity is similar to the diversity observed within each of these clades. The results also show that geographically separated populations of the high-Alpine cave bear form were polyphyletic with respect to their mtDNA. This suggests that small size may have been an ancestral trait in cave bears and that large size evolved at least twice independently.

Animals↗