To cause cancer, tumor suppressor genes require allele(s) to be mutated and therefore are considered The mutation results in a of function.
The correct answer and explanation is :
To cause cancer, tumor suppressor genes require allele(s) to be mutated and therefore are considered “loss of function” mutations.
Explanation:
Tumor suppressor genes are critical for regulating cell growth, repair, and apoptosis (programmed cell death), acting as the brakes on cellular proliferation. These genes encode proteins that help prevent the formation of tumors by inhibiting excessive cell division or repairing damaged DNA. Common tumor suppressor genes include TP53, BRCA1, BRCA2, and APC.
Normally, tumor suppressor genes function by:
- Inhibiting cell cycle progression at checkpoints to ensure proper cell division.
- Inducing apoptosis when cells are damaged beyond repair, preventing them from becoming cancerous.
- Repairing damaged DNA to maintain genetic stability.
A loss of function mutation in a tumor suppressor gene means that the gene no longer produces a functional protein or any protein at all. This mutation can occur in one or both alleles of the gene. However, for a tumor suppressor gene to fully lose its protective function, both copies (alleles) of the gene must typically be mutated (a phenomenon known as the two-hit hypothesis). The first mutation may occur in one allele, but the cell can often still function normally if the second, functional allele is intact. A second mutation in the second allele can completely eliminate the tumor suppressor protein’s activity, leading to uncontrolled cell division, which is a hallmark of cancer.
For example, the TP53 gene, which encodes the p53 protein, is involved in controlling cell cycle checkpoints and apoptosis. When TP53 is mutated, cells with damaged DNA are allowed to continue dividing, which can lead to the accumulation of further mutations and eventually cancer. In hereditary cancers, individuals often inherit one mutated allele, and the second mutation occurs in a somatic cell, triggering cancer development.
Thus, tumor suppressor genes are critical in preventing cancer, and their loss of function due to mutations significantly increases the risk of tumorigenesis.