[1] Many endogenous retroviruses, closely related to exogenous gammaretroviruses, are present in the DNA of mammals (including humans), birds, reptiles and amphibians.

[2] Many also share a conserved RNA structural element called a core encapsidation signal.

The double stranded DNA is highly stable and easily integrated into a host genome.

One specific gammaretrovirus that is commonly used as a retroviral vector is the Moloney murine leukemia virus.

[7][9] A specific gammaretrovirus called xenotropic murine leukemia virus-related virus (XMRV) has been found to infect prostate cancer tissue in laboratories.

[13] Alleged discovery of XMRV in blood cells of patients with chronic fatigue syndrome in 2009 caused a controversy and eventual retraction.

Gammaretroviruses are considered zoonotic viruses because they are found in many different mammalian species, such as mice, cats, pigs, primates, cows, and birds.

The Tursiops truncates endogenous retrovirus original invasion dates back to approximately 10–19 million years ago, and was identified in killer whale endogenous gammaretrovirus which invaded over 3 million years ago.

The nucleocapsid is a nucleic acid protein assembly within the virus particle, it is a substructure of the virion.

Reverse-transcriptase is the enzyme responsible for the transformation of RNA to DNA during the virion replication cycle.

The virus will then begin uncoating, and a linear double-stranded DNA molecule is formed from the single-stranded RNA(+) genome via reverse transcription.

The unspliced viral RNA translation produces env, gag, and gag-pol polyproteins.

Next the virion is assembled in the host cell membrane, and the viral RNA genome is packaged.

This colony is on high alert that their populations of koalas could be extinct in the near future, researchers are concerned that an epidemic may break out in Queensland.

In June 2002, researchers began testing animals for the presence of feline leukemia virus, since the concern arose that viral infection could cause a major health problem in Namibia's cheetah population.

This protein will block replication of some murine leukemia virus strains following reverse transcription.