On the genetic uniqueness of the Ami aborigines of Formosa.

In the attempt to reconstruct the prehistory of Pacific and Indian Ocean populations, Taiwan's aborigines appear to be of particular interest. Linguistic and archeological evidence indicates that the dispersal of Austronesian speakers throughout the islands of Oceania and Southeast Asia may have originated from Taiwan about 5,000 years ago. The Ami are Taiwan's largest aboriginal group. Here, we report on six polymorphic point mutation loci in Ami individuals and compare allelic frequencies to worldwide populations. In order to examine the genetic characteristics and relationships of the Ami aborigines, we used the allelic frequency data to generate expected heterozygosities, power of discrimination values, maximum likelihood phylogenetic trees, principal component maps, and centroid gene flow plots. These analyses argue for the genetic isolation and uniqueness of the Ami people. Data supportive of limited gene flow and/or small population size, as well as genetic similarities to Native Americans, were observed.

Single-nucleotide polymorphism in repetitive sequences of the human deleted in azoospermia complex.

A simple and inexpensive single-nucleotide polymorphism (SNP) analysis procedure is described that uses the Fotodyne Analyst System equipped with the Gel-Pro Analysis software to compare the relative fluorescent intensity of ethidium bromide stained and MboI restricted amplicons from male individuals. The different intensity ratios reflect the ratio of repetitive elements with and without an MboI restriction enzyme site. The polymerase chain reaction (PCR) products represent a reiterated sequence within the Y-linked deleted in azoospermia (DAZ) complex involved in male fertility in humans. This procedure was utilized to determine the ratio of MboI(+) and MboI(-) repetitive sequences in 32 male individuals from two human populations, the Buryat from Mongolia and the Mayan from Yucatan. The proportion of wildtype to mutant amplicons was found to vary from 0 to 100% among individuals. This technique is well suited for large-scale analysis of the locus investigated in this manuscript and other similar polymorphisms. This approach may contribute to the study of recent human evolution based on Y-chromosome analysis as well as medical and developmental issues concerning the significance of these repetitive elements in male infertility.

Single-nucleotide variant in multiple copies of a deleted in azoospermia (DAZ) sequence - a human Y chromosome quantitative polymorphism.

The evolution of the deleted in azoospermia (DAZ) gene family supports prevalent theories on the origin and development of sex chromosomes and sexual dimorphism. The ancestral DAZL gene in human chromosome 3 is known to be involved in germline development of both males and females. The available phylogenetic data suggest that some time after the divergence of the New World and Old World monkey lineages, the DAZL gene, which is found in all mammals, was copied to the Y chromosome of an ancestor to the Old World monkeys, but not New World monkeys. In modern man, the Y-linked DAZ gene complex is located on the distal part of the q arm. It is thought that after being copied to the Y chromosome, and after the divergence of the human and great ape lineages, the DAZ gene in the former underwent internal rearrangements. This included tandem duplications as well as a T > C transition altering an MboI restriction enzyme site in a duplicated sequence. In this study, we report on the ratios of MboI-/MboI+ variant sequences in individuals from seven worldwide human populations (Basque, Benin, Egypt, Formosa, Kungurtug, Oman and Rwanda) in the DAZ complex. The ratio of PCR MboI- and MboI+ amplicons can be used to characterize individuals and populations. Our results show a nonrandom distribution of MboI-/MboI+ sequence ratios in all populations examined, as well as significant differences in ratios between populations when compared pairwise. The multiple ratios imply that there have been more than one recent reorganization events at this locus. Considering the dynamic nature of this locus and its involvement in male fertility, we investigated the extent and distribution of this polymorphism.