degenerate primer

A single-stranded synthetic oligonucleotide designed to hybridize to DNA encoding a particular protein sequence. As the mapping of codons to amino acids is many-to-one, the oligonucleotide must be made as a mixture with several different bases at variable positions. The total number of different oligos in the resulting mixture is known as the degeneracy of the primer. Such primers are widely used in screening a genomic library or in degenerate PCR, to identify homologues of already known genes.