In genetics, complementary DNA (cDNA)'s DNA synthesized from a mature mRNA template in a reaction catalyzed by the enzyme reverse transcriptase. cDNA's often used to clone eukaryotic genes in prokaryotes. When scientists want to express a specific protein in a cell that doesn't normally express that protein (for example, heterologous expression), they'll transfer the cDNA that codes for the protein to the recipient cell. cDNA's also produced by retroviruses (such as HIV-1, HIV-2, Simian Immunod… (More on Cdna)