DNA Science

Genotyping and Interpretation

Short Tandem Repeats (STR) PCR products are labelled with fluorescent dyes, separated and detected by 3100 capillary electrophoresis. The data collection results in a series of fluorescent peaks for each sample.

Genotyping is the process of converting this series of fluorescent peaks into named STR alleles. This is achieved using analysis software (GeneScan & Genotyper) and an analyst's manual interpretation.

Each STR in a sample will consist of either one allele peak (in the case of a homozygote), or 2 allele peaks (in the case of a heterozygote).

The combination of allelic peaks for each of the STR's in a sample is the STR Profile. Alleles are named according to the number of repeat units in the fragment.