Which of these classes of genes is normally involved in positively influencing cellular growth and survival? (Hint: gain of function mutation potentially results in tumor growth).
A None of these answers
B Tumor Suppressors
C Oncogenes
D DNA Repair Genes
The correct answer and explanation is:
The correct answer is C) Oncogenes.
Oncogenes are genes that, when mutated or overexpressed, can drive the uncontrolled growth of cells, contributing to cancer development. These genes are typically involved in promoting cellular growth, survival, and division. In their normal, unmutated form, they regulate processes such as cell signaling, growth factor reception, and intracellular communication. However, when these genes undergo a gain-of-function mutation, they become hyperactive or overly expressed, pushing the cell to divide uncontrollably, leading to tumor formation.
Oncogenes can result from mutations in proto-oncogenes, which are the normal, non-mutated counterparts of oncogenes. Proto-oncogenes help regulate important functions such as cell cycle progression and apoptosis (cell death). A gain-of-function mutation might result in these genes producing an abnormal version of the protein or an excessive amount of it, which leads to tumorigenesis. For example, mutations in genes like HER2 or Ras are common in various cancers.
In contrast, tumor suppressors (B) are genes that normally act to prevent abnormal cell growth and suppress tumor formation. When tumor suppressor genes are mutated, they lose their ability to control cell division and prevent cancer, but tumor suppressors are typically inactivated rather than being overactive.
DNA repair genes (D) are responsible for repairing damaged DNA and maintaining genome stability. Mutations in these genes can also lead to cancer due to the accumulation of DNA errors over time, but their role is not directly related to promoting growth.
Thus, oncogenes are specifically involved in promoting cell growth and survival, and mutations in them can lead to the development of tumors by continuously stimulating the cell cycle.