Question

question 3
you isolate cells from a tumor and study them. you observe that the cells continue dividing, even when dna is damaged, when the cells become crowded, or even when nutrients run low. these observations lead you to suspect that the cells.
a contain a proto - oncogene.
b contain an oncogene.
c contain a mutated tumor - suppressor gene.
d are infected by a virus.
e are breast - cancer cells.
question 4
proto - oncogenes encode proteins that __.
a stimulate cell division.
b suppress tumors.
c restrict cell division.
d control programmed cell death.

Explanation:

• Question 3: Tumor - suppressor genes normally regulate cell growth and division, preventing cells from dividing inappropriately (e.g., when DNA is damaged, cells are crowded, or nutrients are low). If a tumor - suppressor gene is mutated, it loses its function, and cells may continue to divide under these abnormal conditions. Proto - oncogenes (A) are normal genes that can become oncogenes (B) when mutated, but oncogenes typically promote cell division in a more "active" (gain - of - function) way rather than the loss - of - function (tumor - suppressor gene mutation) scenario described. There is no evidence in the question to suggest a viral infection (D) or specifically breast - cancer cells (E).
• Question 4: Proto - oncogenes encode proteins that stimulate cell division. When they are mutated to become oncogenes, this stimulatory function is often enhanced. Tumor - suppressor genes (B) suppress tumors (opposite of proto - oncogenes). Genes that restrict cell division (C) are more in line with the function of normal tumor - suppressor genes (before mutation). Genes controlling programmed cell death (D) are related to apoptosis, not the direct function of proto - oncogenes.

Answer:

Question 3: C. contain a mutated tumor - suppressor gene.
Question 4: A. stimulate cell division.