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 (300+ words):
Tumor suppressor genes play a crucial role in regulating cell growth, DNA repair, and apoptosis (programmed cell death). These genes act as the “brakes” of the cell cycle, ensuring that cells do not proliferate uncontrollably. When functioning properly, tumor suppressor genes prevent the development of cancer by repairing damaged DNA or by initiating cell death in potentially harmful cells.
However, when tumor suppressor genes are inactivated through mutations, this protective mechanism is lost. For cancer to develop due to a tumor suppressor gene, both copies (alleles) of the gene—one inherited from each parent—must be mutated or deleted. This concept is referred to as the “two-hit hypothesis,” which was first proposed by Alfred Knudson in his study of retinoblastoma, a childhood eye cancer. According to this model, a person may inherit one mutated copy of a tumor suppressor gene (the first “hit”) and acquire a second mutation in the other allele later in life (the second “hit”), leading to the loss of gene function and possibly cancer.
Because both alleles must be mutated for the gene to lose its function and lead to cancer, tumor suppressor genes are considered recessive at the cellular level. This is in contrast to oncogenes, which are typically dominant, requiring a mutation in only one allele to promote cancer through a gain of function (e.g., constant cell division signaling).
The mutation in a tumor suppressor gene results in a loss of function, meaning the gene product (usually a protein) no longer performs its normal role in controlling cell proliferation or repairing DNA. Examples of tumor suppressor genes include TP53, RB1, and BRCA1/BRCA2. Loss of function in these genes removes vital checks and balances, increasing the risk of uncontrolled cell growth and tumor formation.
Understanding this mechanism is key in cancer genetics, diagnostics, and developing targeted therapies