An oncogene is

a- a viral gene with no relation to the host cell's gene
b- a mutated form of a proto- oncogene
c- a bacterial gene that causes cancer in the host
d- a gene that turns off cellular reproduction

Correct B

Hint: "proto-" means "original" or "primitive" --> like a PROTOtype is an original design idea for a product

When a proto-oncogene mutates it can become an oncogene (a gene that, when expressed, blocks normal cell death and therefore allows an irregular cell to continue to survive and proliferate). Cancerous tumors can then form as this cell continues to grow uncontrollable and divide.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.