Also get revertants resulting in deletion of the retrovirus, and restoration of the dark coat color. The presence of the retrovirus causes abberant splicing. 4.Insertion of proviral genes may result in new antigenic specificty on the cells. or resistance to infection by other retroviruses. 5.Evolutionary spreading of the virus through the host genome by reverse trancriptase. Some proviruses are under very tight cellular control.they never express themselves under normal conditions, but can be induced by a variety of chemicals,including halogenated deoxyriboside, mitogens inhibitors of protein synthesis etc.
Different inducers induce different endogenous retroviruses.
Viral infection with complex etiology. 1963 it was observed that one type of cancer predominated in E.Africa. This was Burkitt's lymphoma. It was endemic in certain areas, and originally suggested that it was associated with insect transmission. In 1967 a similar disease found in New Guinea,with similar type of distribution.