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.
Når forskere ønsker at udtrykke et specifikt protein i en celle, der ikke normalt udtrykker det protein (dvs. et heterologt udtryk), vil de overføre den cDNA, der koder for proteinet, til modtagercellen. cDNA produceres også naturligt af retrovira (såsom HIV-1, HIV-2, Simian Immunodeficiency Virus, osv.) og integreres derefter i værtens genom, hvor det skaber en provirus.