The gene Src normally is activated by extracellular signals called growth factors. When the growth factors are present, Src instructs the cell to divide. A mutant form of Src is found in many cancer tumors. The mutant form of Src is active in the absence of growth factors. The mutated Src is a

A. Tumor suppressor gene

B. Oncogene

C. Cancer gene

D. Proto-oncogene

B. Oncogene

Explanation:

A gene that makes the body cells to divide in an uncontrolled manner is called an oncogene. An oncogene is responsible for the development of tumors due to disturbed regulation of cell division. The gene src makes the cells to enter the process of cell division in response to the growth factors.

However, the mutant src gene does not require the presence of growth factors and signals the cells to enter the process of cell division even in the absence of the growth factors. Since the mutant src gene causes uncontrolled cell division, it represents an oncogene.