Figure E.1 illustrates the results of an electrophoretic analysis of 13 CODIS STR markers on a DNA sample and identifies the alleles for each gene. Table E.2 lists the frequencies for alleles of three of the STRs shown in the figure. Use this information to calculate the frequency of the genotype for STR genes FGA, vWA, and D3S1358 given in Figure E.1.

Key Concepts

Electrophoresis

Electrophoresis is a laboratory technique used to separate DNA fragments based on their size and charge. In the context of genetic analysis, it allows for the visualization of specific DNA markers, such as Short Tandem Repeats (STRs), which are crucial for forensic and paternity testing. The results can indicate the presence of different alleles at specific loci, which are essential for calculating genotype frequencies.

Short Tandem Repeats (STRs)

Short Tandem Repeats (STRs) are repeating sequences of 2-6 base pairs of DNA that are highly variable among individuals. These variations make STRs useful for genetic profiling, as they can serve as genetic markers. Each individual inherits two alleles for each STR locus, one from each parent, and the combination of these alleles constitutes the individual's genotype.

Genotype Frequency Calculation

Genotype frequency calculation involves determining how common a specific genotype is within a population. This is done by multiplying the frequencies of the alleles that make up the genotype, according to the Hardy-Weinberg principle. For example, if the frequencies of two alleles at a locus are known, the frequency of the homozygous genotype can be calculated by squaring the frequency of one allele and multiplying it by the frequency of the other allele for heterozygous genotypes.