Every STR has multiple alleles, or variants, each defined by the number of repeat units present or by the length of the sequence. ... Flanking regions are important because knowing their sequences enables geneticists to isolate the STR using polymerase chain reaction, or PCR, amplification.

Why are flanking sequences important?

Flanking regions of the gene are often found to be of importance in determining the pattern and level of expression of the gene. ... The site of expression of a gene may be influenced by factors other than the patterns of expression of tissue–specific transcription factors.

What is flanking sequence in PCR?

Two primers are used in each PCR reaction, and they are designed so that they flank the target region (region that should be copied). That is, they are given sequences that will make them bind to opposite strands of the template DNA, just at the edges of the region to be copied.