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:
Correct Answer:
To cause cancer, tumor suppressor genes require both alleles to be mutated and therefore are considered recessive. The mutation results in a loss of function.
Explanation:
Tumor suppressor genes are a critical component of the body’s defense system against cancer. These genes normally function to regulate cell growth, repair DNA damage, and ensure that cells with severe damage undergo apoptosis (programmed cell death). When tumor suppressor genes are working properly, they prevent the uncontrolled cell proliferation that characterizes cancer.
For a tumor suppressor gene to contribute to cancer development, both copies (alleles) of the gene must typically be inactivated or mutated. This concept follows the “two-hit hypothesis”, first proposed by Alfred Knudson in the context of retinoblastoma, a childhood eye cancer. According to this hypothesis, the inactivation of both alleles of a tumor suppressor gene is necessary for the loss of function and subsequent progression toward cancer.
These genes are described as recessive at the cellular level because a mutation in just one allele does not usually result in a functional loss. The remaining normal allele is typically sufficient to maintain control over cell proliferation. However, when both alleles are mutated, the regulatory function is lost, allowing the cell to divide uncontrollably.
Furthermore, the mutation in tumor suppressor genes leads to a loss of function, as opposed to oncogenes, which cause cancer through a gain of function mutation. In oncogenes, a mutation in just one allele can drive cancerous changes because the resulting protein actively promotes cell growth or survival.
Examples of important tumor suppressor genes include TP53, RB1, BRCA1, and BRCA2. Mutations in these genes can significantly increase the risk for various types of cancer.
In summary, tumor suppressor genes contribute to cancer when both alleles are mutated (recessive), resulting in a loss of function, thereby removing critical regulatory mechanisms that prevent tumor growth.