DNA sequences

Short Tandem Repeats (STRs)

Short Tandem Repeats are short stretches of DNA, usually several hundred bases long, which contain repeated sequences.

This STR has repeats of the bases TTAT:

The repeats in STRs can be of any length, from 2:

or 3:

to 50 or more bases, but 4 base repeats are the easiest to work with using current techniques.

Different versions, or alleles,of STRs have different numbers of repeats. Allele 3 of this STR has 3 repeats of the sequence TTAT, and a total length of 30 bases in the DNA segment:

Allele 4 has 4 repeats, and a total length of 34 bases:

Allele 5 has 5 repeats, and a total length of 38 bases:

What is the length of allele 6?

DNA EVIDENCE

Short Tandem Repeats (STRs)