- 01 Introduction
- 02 Biology of DNA
- 03 Practical Issues Specific to DNA Evidence
- 04 Introduction to the Forensic DNA Laboratory
- 05 Assuring Quality in DNA Testing
- 06 Understanding a Forensic DNA Lab Report
- 07 Statistics and Population Genetics
- 08 Mitochondrial DNA & Y-STR Analysis
- 09 Forensic DNA Databases
- 10 Collection of DNA Evidence from Suspects and Arrestees
- 11 Pretrial DNA Evidence Issues
- 12 Victim Issues
- 13 Trial Presentation
- 14 Postconviction DNA Cases
- 15 Emerging Trends
Principles of Forensic DNA
for Officers of the Court
for Officers of the Court
Module 7 :: Statistics
Topic 3 :: Determination of Allele Frequencies
Estimating STR Profile Frequencies—The Product Rule
The product rule is used to estimate the chance of finding a given STR profile within a population. This is done by multiplying the frequency of each of the genotypes (combination of alleles) found at all loci in the STR profile.
In the case of Y-chromosome STRs and mitochondrial DNA (mtDNA) the product rule can not be used. For more information on Y-STRs and mtDNA, refer to Module 8.
The product rule requires using formulas defined by "Hardy-Weinberg Equilibrium," which predicts the probability of observing a particular homozygote (same allele inherited from each parent) profile or a heterozygote (different allele inherited from each parent) profile in a population.
Click here to view an example of how the product rule is used.
