Question

Explain why an oncogene is associated with a gain-of-function and a mutation in a tumor suppressor gene is associated with a loss-of-function.

Short answer

An oncogene is associated with a gain-of-function because a mutation or overexpression of the gene can enhance the cell’s ability to proliferate and grow. A mutation in a tumor suppressor gene, however, is associated with a loss-of-function, because the gene loses its ability to regulate cell division and prevent the formation of tumors.

Step-by-step solution

Understanding Oncogenes

Oncogenes are genes that have the potential to transform a cell into a tumor cell. In normal cells, these genes promote cell growth and division. However, when mutated or overexpressed, they can cause cells to divide uncontrollably and become cancerous. A gain-of-function mutation implies that the oncogene is activated, meaning it's doing more than it should be, leading to overstimulation of cell proliferation and growth.

Understanding Tumor Suppressor Genes

Tumor suppressor genes normally help keep cell division under control or repair DNA mistakes. When a tumor suppressor gene is functioning correctly, it helps regulate the cell cycle, prevent uncontrolled cell growth, and helps trigger apoptosis or programmed cell death. However, a loss-of-function mutation implies that the gene is not working properly or has been switched off, meaning it is unable to carry out its usual role. This lack of control can lead to increased cell division and the development of tumors.