Interpreting Single-Source Profiles

Question 1

What differences will we see in a crime scene profile and a reference sample profile?

Answer 1

• There are two types of samples with differing quality issues associated with each.
  
  • We should not anticipate seeing a mixture in a reference sample.
  • In the case of the crime scene sample, it is not unusual to have mixed and degraded DNA

Question 2

What is random match probability?

Answer 2

What is the (a) chance that a (b) randomly chosen, (c) unrelated person (d) might happen to have the same DNA profile (e) that we find associated with an evidence sample?

Question 3

What is the product rule for heterozygous loci?

Answer 3

• The formula is simply 2 x P x Q
• At any loci where the individual is heterozygous

P is the frequency of the alleles we find in this particular profile at this locus.

Q is the frequency of one of the alleles we find in this particular profile at this locus.

Question 4

What is the product rule for homozygous loci?

Answer 4

The formula used when an individual is homozygous at a locus is P²

We multiply the frequency of P by itself.