Question

QUESTION 28

Certain viruses are instrumental in converting proto-oncogenes to oncogenes. This conversion most commonly results because:

A. the proto-oncogenes are more likely to undergo mutation or recombination within a virus.

B. viruses contain the remainder part of the DNA that is added to the proto-oncogene to form the oncogene.

C. only viruses contain genes that can convert proto-oncogenes into oncogenes.

D. viruses specifically infect cells that contain proto-oncogenes.

Answer 1

The correct answer is (A). The proto-oncogenes are more likely to undergo mutation or recombination within a virus. The oncoviruses incorporate the proto-oncogene into their own genome. Then, such a transduced gene undergoes mutation and gets converted into an oncogene. These genes which were previously inactive turn active by the mutation. They may also undergo recombination to become transcriptionally active. Examples of such genes are v-myc and c-myc.

Other options are incorrect. Viruses don't contain the remainder part of human proto-oncogenes. Rather, they take it up from host itself. Other factors could also cause activation of proto-oncogenes. Chromosome rearrangements, gene amplification are involved in the process. Proto-oncogenes are present in all cells. They have the function of cell cycle regulation and play a role in cell death. Thus, virus do not specifically affect them.