STR (Short Tandem Repeat) | DNA Testing Glossary
A short tandem repeat (STR) is a type of genetic marker where a short sequence of DNA — usually 2 to 6 base pairs long — repeats in a row at a specific location on a chromosome. The number of repeats varies from person to person, making STRs useful for distinguishing individuals. STR analysis is the standard method used in DNA relationship testing and forensic identification, including the FBI's CODIS database. During a paternity test, the lab examines STR loci in both the child and the alleged father. Because a child inherits one copy of each STR from each biological parent, matching repeat counts across multiple loci provides strong evidence of a biological relationship.
Related Terms
Genetic Marker, Locus, Allele, PCR (Polymerase Chain Reaction), Electropherogram
