Question

Why are some viral and cellular oncogenes so similar to each other? Retroviruses do not need oncogenes to survive and replicate so why do some viruses have oncogenes?

Answer 1

Because proto-oncogenes are involved in the process of cell growth, they can turn into oncogenes when a mutation permanently activates the gene. In other words, oncogenes are mutated forms of proto-oncogenes. The mutation could be the result of virus invasion.

Viral oncogenes were first discovered in animal tumor viruses and correspond to mammalian genes that have been incorporated into the viral genome through genetic recombination. Alterations in the coding sequence of these genes result in constitutively active proteins that are expressed as viral oncogenes.