high-molecular-weight DNA Human Identification
In the early days of DNA-based identification, the hypervariable regions of interest were variable number tandem repeat (VNTR) loci, which had a high level of heterozygosity and were relatively large in size (300–10,000bp) (Nakamura et al., 1987; Budowle et al., 1991). VNTRs were analyzed using restriction fragment length polymorphism (RFLP), where high-molecular-weight target DNA is digested with a restriction enzyme that has recognition sites at both ends of the hypervariable region. The size of the DNA fragment resulting from the restriction enzyme digestion is dictated by the number of repeat elements. These fragments are separated by size using agarose or polyacrylamide gel electrophoresis and detected using a labeled VNTR probe. Analysis of multiple VNTR loci results in a unique pattern of DNA fragments on the gel. The patterns generated from a DNA sample of unknown origin and DNA of known origin are compared. Matching patterns indicate that the sources of the unknown and known DNA samples are likely the same. RFLP analysis of VNTR loci works well to resolve immigration and paternity disputes and for other applications where large amounts of intact DNA can be collected. However, RFLP is not ideally suited to forensic investigations because microgram amounts of high-molecular-weight DNA are required.Thus, VNTR analysis is limited to investigations where large amounts of DNA are recovered.
In the early days of DNA-based identification, the hypervariable regions of interest were variable number tandem repeat (VNTR) loci, which had a high level of heterozygosity and were relatively large in size (300–10,000bp) (Nakamura et al., 1987; Budowle et al., 1991). VNTRs were analyzed using restriction fragment length polymorphism (RFLP), where high-molecular-weight target DNA is digested with a restriction enzyme that has recognition sites at both ends of the hypervariable region. The size of the DNA fragment resulting from the restriction enzyme digestion is dictated by the number of repeat elements. These fragments are separated by size using agarose or polyacrylamide gel electrophoresis and detected using a labeled VNTR probe. Analysis of multiple VNTR loci results in a unique pattern of DNA fragments on the gel. The patterns generated from a DNA sample of unknown origin and DNA of known origin are compared. Matching patterns indicate that the sources of the unknown and known DNA samples are likely the same. RFLP analysis of VNTR loci works well to resolve immigration and paternity disputes and for other applications where large amounts of intact DNA can be collected. However, RFLP is not ideally suited to forensic investigations because microgram amounts of high-molecular-weight DNA are required.Thus, VNTR analysis is limited to investigations where large amounts of DNA are recovered.
