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Allelic frequencies of two DNA restriction fragment length polymorphism systems collected from an undefined population : application to DNA profiling Bonnycastle, Lori L.C.


Restriction fragment length polymorphisms (RFLPs) within the deoxyribonucleic acid molecule were analysed to determine the extent of their ability to provide discriminating human DNA profiles for forensic identification. The two types of RFLPs studied were variable number of tandem repeats (VNTR), the technique commonly used by North American forensic laboratories, and dimorphic restriction endonuclease recognition site (RES) developed in this laboratory. Data bases showing allele frequencies were collected for four VNTR hypervariable regions, D2S44, D16S85, INS, and D14S13 from an undefined population group obtained from the Greater Vancouver Area. Allele frequency distributions from this group were similar to the larger and more statistically defined allele distributions obtained by other laboratories, the RCMP Molecular Biology Unit in Ottawa and Promega associated laboratories in all of which analysed Caucasian populations. An alternative technology to VNTR was based on the selection of five regions within the human genome that contain dimorphic restriction endonuclease recognition sites (RES). A nucleotide sequence of approximately one kilobase that contained the RES was selected from the genes of the following proteins: adenine phosphoribosyltransferase (APRT), prealbumin (PALB), adenine deaminase (ADA), carbonic anhydrase II (CAH) and lipoprotein lipase (LPL). After amplification of the nucleotide sequence by the polymerase chain reaction (PCR), the presence or absence of the internal RES was analysed by restriction endonuclease digestion followed by agarose gel electrophoresis. From the pattern (size and number) of the restriction fragments generated, it is possible to make genotype assignments with respect to the RES. Restriction endonuclease activity was monitored by the presence of a control DNA fragment which is also cleaved by the restriction endonuclease used for each specific analysis. Statistical calculations demonstrated that by using 16 unlinked dimorphic RES, rapid individual identification to a certainty of one in 6.5 million is possible. Analysis of casework and/or laboratory simulated forensic specimens indicate that both the VNTR and RES system are discriminating and can be applied to non-ideal specimens. However, the RES system offers a much simpler and more reliable methodology.

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