M. Pescarmona

A Study of Y-Chromosome Microsatellite Variation in Sub-Saharan Africa: A Comparison between F ST and R ST Genetic Distances

Seven Y-chromosome microsatellite loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393) were analyzed in three populations from sub-Saharan Africa: the Bamileke and Ewondo populations from Cameroon and the Hutu from Rwanda. Complete typing was obtained for 112 individuals, and a total of 53 different haplotypes was observed. The single-locus gene diversity, averaged across populations, ranges from 0.100 for the DYS392 locus to 0.610 for the DYS389I locus. The haplotype diversity ranges from 0.832 (Ewondo) to 0.965 (Hutu), with an intermediate value of 0.918 in the Bamileke. The diversity among Bamileke, Ewondo, Hutu, and other sub-Saharan populations selected from the literature was analyzed using both a classical (FST) and a stepwise-based (RST) genetic distance method. The pattern of interpopulational diversity based on FST was congruent with anthropological knowledge, while that based on RST revealed unexpected and unconvincing population affinities. From a practical point of view, our study indicates that Y-chromosome microsatellite data may provide useful information for analyses of interpopulational diversity among sub-Saharan populations if an adequate number of loci and individuals along with an appropriate genetic distance method are used. On a theoretical ground, we propose that the lesser performance of RST compared to FST could be explained by the important role played by genetic drift in shaping the relationships among examined populations.

Estimating allele frequencies of hypervariable DNA systems

Several polymorphisms of human DNA have been shown to be hypervariable due to the recurrence of a variable number of tandem repeats (VNTRs) in the lengths of allelic restriction fragments. The recurrence of allelic variants in this novel class of polymorphisms seems to comply well with a model of continuous random variables. Based on this assumption, we have compiled some simple algorithms for classification of continuous data and estimation of classes of relative frequencies and have implemented these routines for the management of databases storing hypervariable single locus DNA genetic systems. The algorithms are compiled in BASIC language and can be incorporated in task-oriented computer programs. Three procedures are discussed, based in turn on: (a) using predetermined, arbitrary classes; (b) point estimations of frequencies for single fragments using error measurements associated with the kilobase value assignment; (c) estimates of phenotype frequencies according to error measurements. Error measurements are obtained from a statistic of values pertaining to several restriction fragments (genomic controls) repeatedly tested in different experiments. Problems related to these approaches are discussed.

A repository of 14 PCR-loci Italian gene frequencies in the world wide web

A collection of 6830 typing results produced by the Immunohematology Laboratory at the UCSC, pertaining to 11 STRs (FES/FPS, vWA31, HUMTH01, F13A1, MBP, D21S11, D7S460, D18S51, CD4, TPOX, CSF1PO) and 3 AmpFLPs (D1S80, APO-B, COL2A1), is publicly available as an electronic archive at a website.

Exclusion of an individual charged with rape by allele-specific DNA profiling on fetal tissues

A mentally handicapped young woman was raped by an unknown individual, who repeatedly abused of her. The crime was discovered only after she fell pregnant and aborted. By gestational age (16–18 weeks), the fetus was assumed to have been conceived when the woman was hospitalized. Hencefrom, a nurse was suspected to be her rapist, and was prosecuted. During the trial, our laboratory was asked to perform DNA profiles over some fetal tissues, the woman and the suspect. Following the analysis detailed here, evidence was given that the alleged rapist could not be the father.

Allele frequencies distribution of two VNTR markers (YNH24; YNZ22) in PST I digests from random Italian individuals (population of Rome)

Since the first report of a highly polymorphic locus in Man (Wyman and White, 1980), numerous hypervariable DNA sequences have been described. These markers have been given the name VNTR (Nakamura et al, 1987), and represent nowaday a major tool in forensic biology and paternity testings.

On the effectiveness of three DNA probes in hybridization experiments over HINF I blots containing aged/degraded samples

Several DNA probes recognizing variable number of tandem repeats (VNTR) polymorphisms have been recently introduced in the analysis of forensic specimens. They include lambda MS1/31/43/G3 (Wong et al, 1987), alpha globin 3’HVR (Fowler et al, 1988) and YNH24 (Nakamura et al, 1987).