What is "complementary dna"

n. single-stranded DNA that is complementary to messenger RNA or DNA that has been synthesized from messenger RNA by reverse transcriptase [syn: cDNA]

In genetics, complementary DNA (cDNA) is double-stranded DNA synthesized from a single stranded RNA (e.g., messenger RNA ( mRNA) or microRNA ( microRNA)) template in a reaction catalysed by the enzyme reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes. When scientists want to express a specific protein in a cell that does not normally express that protein (i.e., heterologous expression), they will transfer the cDNA that codes for the protein to the recipient cell. cDNA is also produced naturally by retroviruses (such as HIV-1, HIV-2, Simian Immunodeficiency Virus, etc.) and then integrated into the host's genome, where it creates a provirus.

The term cDNA is also used, typically in a bioinformatics context, to refer to an mRNA transcript's sequence, expressed as DNA bases (GCAT) rather than RNA bases (GCAU).

The number of introns present in a cDNA is zero, since it is derived from eukaryotic mRNA which does not contain introns (polycistronic).