Question

a researcher isolates cells from a tumor and studies them. the researcher observes that the cells continue dividing, even when dna is damaged, when the cells become crowded, or even when nutrients run low. these observations lead the researcher to suspect that the cells:

• contain a proto - oncogene.
• contain a mutated tumor suppressor gene.
• are breast cancer cells.
• are infected by a virus.
• contain an oncogene.

Explanation:

Tumor suppressor genes regulate cell growth. When mutated, they lose this function, allowing cells to divide uncontrollably (even with DNA damage, crowding, or low nutrients). Proto - oncogenes (when mutated become oncogenes) promote cell growth but the key here is the loss of regulation (tumor suppressor gene role). Breast cancer cells are too specific without evidence. Viral infection is not indicated. Oncogenes promote growth but the description aligns more with loss of tumor suppressor function.

Answer:

contain a mutated tumor suppressor gene.