Question

The frequency of alleles left behind at a crime scene are below. A suspect has all of those alleles (he is a match for all 4 alleles). What is the likelihood he would match the crime scene sample by chance?

Allele   Frequency of allele in the population
DSTF8   0.02
DSTF3   0.15
AFBM9   0.22
AFBM4   0.05
Hint: each allele is an independent event.

Answer 1

There are four alleles DSTF8, DSTF3, AFBM9, and AFBM4 that are present at the crime scene. Let the frequency of these alleles occurring in the population be p(A), p(B), p(C), and p(D), respectively.

Hence, we have:

Now, each allele occurs independently of each other. Hence the frequency that an individual will have all the four alleles will be:

Thus, the likelihood of the individual has all the four alleles is