Opinion ID: 1506658
Heading Depth: 1
Heading Rank: 37

Heading: The Polymarker (PM) Test

Text: The PM test works like the DQ Alpha test, but instead of testing for the composition of one gene, it tests for six genes. The six genes tested in the PM test are: LDLR (low density lipoprotein receptor), GYPA (glycophorin A), HBGG (hemoglobin gammaglobulin), D7S8, and GC (Group Component). Each of those genes consists of combinations of either two or three different alleles. A blue-dot test, similar to that used in the DQ Alpha test, determines the genotype for each gene. As explained by Ms. Cooper, one of the State's experts, the PCR test begins by amplifying the amount of DNA. Then, the DNA is passed over a polymere test strip. When the DNA finds its type on that locus, the dot changes color. Each combination of alleles is associated with a population frequency that is expressed as a percentage. After ascertaining a sample's genotypes and population frequencies for each of the five individual genes, a mathematical formula known as the product rule reveals the likelihood that another individual in the relevant population would share the test subject's genotype for all five targeted genes. The product rule, which gives the profile frequency in a population as a product of coefficients and allele frequencies, rests on the assumption that a population can be treated as a single, randomly mating unit. NRC Report, supra, at 5. Under the product rule, the population frequencies for each of the six genotypes are multiplied by one another. Defendant's genotype for LDLR is present in 56% of the African-American population, his GYPA in 50%, his HBGG in 27%, his D7S8 in 45%, his GC in 17%, and his DQ Alpha in 11.9%. Applying the product rule, the prosecution's expert testified that one-in-170 African Americans would share defendant's genotype for the LDLR, GYPA, HBGG, D7S8, and GC loci. The product rule equation would be: .56 x .5 x .27 x .45 x .17 = .0058, or, expressed as a ratio, about one-in-170 African Americans. By including defendant's DQ Alpha genotype frequency in the product rule equation along with the polymarker loci, only one-in-1400 African Americans would share defendant's composite genotype for all six genes. The product rule equation would be: .56 x .5 x .27 x .45 x .17 x .119 = .00069. Expressed as a ratio, the result is about one-in-1400 African Americans.