A 'gammaretrovirus' is a
genus of the
retroviridae family. Many species contain
oncogenes and cause
sarcomas and
leukemias.
Examples are the
murine leukemia virus, the
feline leukemia virus, the
feline sarcoma virus, and the avian
reticuloendotheliosis viruses.
Many
endogenous retroviruses, closely related to exogenous gammaretroviruses are present in the DNA of mammals (including humans), birds, reptiles and amphibians.