“I think this is interesting, because when notice like this is taken, and a direction initiated, things can build up steam quickly! Especially when the government (FDA for instance) is involved.”[/B]
HLA DNA TYPING The HLA loci are the most polymorphic genes in the human genome (the HLA-B locus has > 800 alleles) and there are extensive datasets (i.e. dbMHC, curated by the NCBI) on the frequency distributions of allelic variants in many different human populations.1,2Much of these data were generated as part of an international collaboration (the genetic diversity/anthropology component of the 13thand 14thInternational Histocom-patibility Workshops) coordinated by our colleague, Dr. Steve Mack. These genetic typings of population samples were all carried out using a technology we had developed in the late 1980s that involved the PCR amplification of HLA genes from the DNA sample using labeled (biotinylated) oligonucleotide primers. The labeled and amplified target DNA was then denatured and hybridized to an immobilized panel of oligonucleotide probes on a nylon membrane (the linear array assay). The pattern of probe binding to the amplified target DNA was then detected using streptavidin-HRP and a chromogenic substrate. The HLA genotype could then be determined by the pattern of blue lines (probe binding to target DNA), not unlike a barcode. In fact it was our genetic typing of an HLA gene, the HLA-DQA1 locus, using this PCR/probe technology that was the basis for the first forensic use of DNA typing in the United States (Pennsylvania v. Pestinikis, 1986) as well as the first post-conviction review case (Gary Dotson Case, Illinois, 1987). This HLA-DQA1 forensics test became the first commercial PCR test in 1991. Our current HLA typing systems are significantly more informative (more probes, more distinguishable alleles) than our initial HLA-DQA1 test. We were able to PCR amplify and type the HLA-DRB1, the HLA-DQB1, and the HLA-B loci from the sample provided by Sgt. Dostie. In the four digit nomenclature for the HLA loci, the HLA-DRB1 genotype was DRB1*0407/*0407, the DQB1 genotype was DQB1*0302/*0302 and the HLA-B genotype was B*3905/*3905. Thus, this sample was homozygous for each HLA locus typed. The frequency of this genotype is extremely rare in most global populations (< 0.01% for DRB1 and DQB1) while it is much higher in Native American populations from Mexico (20-30% for a Mayan population) and Central America. For Native Americans in North America, the genotype frequency is 1-2% and among various Asian populations ranges from 0.01-0.04%. The observed HLA-B genotype of the DNA sample is also much more frequent in Native Americans from Mexico and Central America than in other parts of the world. Because the HLA-B locus is linked to and is in linkage disequilibrium with the HLA-DRB1 and DQB1 loci, the frequencies of alleles at these loci are not statistically independent so that the probabilities of being in a given population group based on the individual loci cannot be multiplied. Based on the population frequencies of HLA-B-DRB1-DQB1 haplotypes, the data from HLA-B genotyping are consistent with and strengthen the inference of geographic origin based on HLA-DRB1 and DQB1 genotyping. Our interpretation of the HLA typing data is that Mexico and Central America are the most likely geographic origin for the Native American individual whose body was found in the grave in the Shady Rest campground.
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