Question

Ras is a GTP-binding protein that is often defective in cancer cells. A common

mutation found in cancer cells causes Ras to behave as though it were bound to
GTP all the time, which will cause cells to divide inappropriately. From this
description, the normal Ras gene is _______.
(a) a tumor suppressor.
(b) an oncogene.
(c) a proto-oncogene.
(d) a gain-of-function mutation.

Answer 1

The normal Ras gene is a proto-oncogene, which can mutate to become an oncogene, contributing to the growth of cancer cells through unregulated cell division when it behaves as if permanently bound to GTP.

Step-by-step explanation:

The normal Ras gene is best described as a proto-oncogene. Proto-oncogenes are genes that normally help cells grow. When a proto-oncogene mutates (changes) or there are too many copies of it, it becomes a sort of 'bad' gene that can become permanently turned on or activated when it is not supposed to be. When this happens, the gene can become an oncogene, which can lead to the growth of cancer cells. In the case of Ras, a common mutation found in cancer cells causes Ras to behave as though it were continuously bound to GTP. This mutation in the Ras gene means it no longer properly regulates cell division, forcing the cell into a state of uncontrolled proliferation which is a characteristic of cancer. The correct answer to the question is therefore (c) a proto-oncogene.