Of the two classes of genes associated with cancer, tumor-suppressor genes and oncogenes, mutations in which group can be considered gain-of-function mutations? In which group are the loss-of-function mutations? Explain.

Verified step by step guidance

1. Understand the two classes of genes associated with cancer: tumor-suppressor genes and oncogenes. Tumor-suppressor genes normally act to inhibit cell division or promote apoptosis, preventing uncontrolled cell growth. Oncogenes, on the other hand, promote cell division and survival when activated.
2. Recall the definitions of gain-of-function and loss-of-function mutations. Gain-of-function mutations result in a gene product with enhanced or new activity, while loss-of-function mutations reduce or eliminate the normal activity of the gene product.
3. Analyze oncogenes: mutations in oncogenes typically lead to gain-of-function, meaning the mutated gene is overactive or constitutively active, driving excessive cell proliferation. This is because oncogenes are like the 'gas pedal' for cell growth.
4. Analyze tumor-suppressor genes: mutations here are usually loss-of-function, meaning the gene loses its ability to regulate or inhibit cell growth. This loss removes the 'brakes' on cell division, allowing uncontrolled growth.
5. Summarize that gain-of-function mutations are characteristic of oncogenes, while loss-of-function mutations are characteristic of tumor-suppressor genes, explaining their roles in cancer development.

Key Concepts

Oncogenes and Gain-of-Function Mutations

Oncogenes are mutated forms of proto-oncogenes that promote cell growth and division. Gain-of-function mutations in these genes lead to their overactivation or constant activity, driving uncontrolled cell proliferation and contributing to cancer development.

Tumor-Suppressor Genes and Loss-of-Function Mutations

Tumor-suppressor genes normally inhibit cell growth or promote apoptosis to prevent tumor formation. Loss-of-function mutations in these genes disable their protective roles, allowing cells to grow unchecked and increasing cancer risk.

Difference Between Gain- and Loss-of-Function Mutations

Gain-of-function mutations enhance or create new gene activity, often dominant in oncogenes, while loss-of-function mutations reduce or eliminate gene activity, typically recessive in tumor-suppressor genes. Understanding this distinction is key to grasping how different gene classes contribute to cancer.