Short for complementary DNA. Term used for any DNA sequence which was reverse transcribed from RNA. The enzyme which does this is called reverse transcriptase. The DNA strand will bind the RNA strand it was created from. Creation of cDNAs is helpful in finding useful genes. A large collection of mRNAs from cells can be reverse transcribed, giving a cDNA with the approximate sequence of their original genes (minus introns). These cDNAs can then be used as probes to find the location of the original gene on a chromosome. HIV also creates a cDNA of its RNA genome as part of its cycle of infection.