A gene that codes for a positive cell cycle regulator is called a(n)_. a. kinase inhibitor b. tumor suppressor gene c. proto-oncogene d. oncogene
The Correct Answer and Explanation is:
The correct answer is c. proto-oncogene.
Explanation:
Proto-oncogenes are genes that play a critical role in regulating the cell cycle and normal cell growth. These genes code for proteins that promote cell division and prevent cell death, which is essential for normal development, tissue maintenance, and repair.
Proto-oncogenes are essentially “precursors” to oncogenes. When a proto-oncogene undergoes mutations or overexpression, it can transform into an oncogene, which has the potential to drive uncontrolled cell division, leading to cancer. This transformation often involves changes that increase the activity or amount of the protein product of the gene, resulting in abnormal cell growth.
For instance, proto-oncogenes often code for growth factors, receptors, or proteins involved in signal transduction pathways that regulate cell division. One well-known example is the ras gene, a proto-oncogene that encodes a protein involved in cell signaling pathways. Mutations in the ras gene can cause it to become constitutively active, leading to unchecked cell division and potentially contributing to the development of tumors.
While oncogenes are mutated versions of proto-oncogenes, causing them to promote excessive cell growth and division, tumor suppressor genes do the opposite. They help prevent cells from becoming cancerous by inhibiting cell division or promoting cell death (apoptosis). Kinase inhibitors are not directly related to the gene itself but are substances that can inhibit specific kinases involved in the regulation of the cell cycle.
In summary, proto-oncogenes are normal genes that, when altered, can become oncogenes and lead to cancer by promoting abnormal cell growth.
