Glossary of str terms and definitions

Below is a listing of terms and definitions most commonly used in our STR analysis reports. 

Allelic polymorphism: Allelic polymorphism is counting each of the heterozygous peaks and homozygous peaks in each sample and adding those together.  Each homozygous peak counts as 1, and each heterozygous peak counts as 2.

Allelic Imbalance
: Allelic Imbalance is reported when one allele is expressed 50% or greater than the other. Usually it corresponds to amplification, duplication or polyploidy within certain regions or an entire chromosome.

Partial profile
: A partial profile is noted when not all the alleles are able to be called from our raw data analysis.  Partial profiles are due in large part to low quality DNA, or an error during the amplification portion of the STR protocol.

t:  Microvariants are alleles that are not exact multiples of the basic repeat motif or sequence variants of the repeat motif or both.  Alleles with partial repeat units are designated by the number of full repeats and then a decimal point followed by the number of bases in the partial repeat

What raw data looks like:  

The GeneMapper software that we use for analysis converts the number of repeats at each loci into peaks, visualized as different colors. We use an allelic ladder that provides a standard of common alleles. Two peaks at a given loci represent a heterozygous genotype while one peak is homozygous. The top number in the small box under each peak is the number of repeats. A partial repeat would be a number with a decimal. The bottom number is the peak area. Allelic imbalances are determined using the peak areas, and if that expression level is discordant between the two alleles then we call that an allelic imbalance. Generally, we make an imbalance call when the area of one peak at a given loci is less than 50% of the area of the other. Allelic imbalance could be the result of chromosomal gains, losses, and/or amplification in a cell line.