At an autosomal STR locus, allele 12 has a population frequency of 0.02. An evidence sample shows the genotype 12,12 and matches the suspect at this locus alone. Assuming Hardy-Weinberg equilibrium and unrelated individuals, what is the random match probability at this single locus?
- A 0.04
- B 0.02
- C 0.0004 ✓
- D 0.00008
Correct answer: C. 0.0004
Explanation
For a homozygous genotype under Hardy-Weinberg equilibrium the genotype frequency equals the square of the allele frequency: 0.02 squared gives 0.0004, meaning roughly 1 person in 2500 would share this genotype by chance. Option A applies 2p, which is the heterozygote frequency formula, and option B simply restates the allele frequency. Full casework multiplies such single-locus values across all typed loci.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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