In the theory of carcinogenesis, the inactivation of which genes contributes to cancer?

The theory of carcinogenesis involves multiple genetic changes that lead to the development of cancer, particularly through the inactivation of certain types of genes. Tumor-suppressor genes and DNA repair genes are critical in this process.

Tumor-suppressor genes, when functioning normally, regulate cell division and can prevent tumor formation. If these genes are inactivated, cells can grow uncontrollably because the checks and balances that typically prevent excessive cell proliferation are lost. Classic examples include the p53 gene, which is involved in cell cycle regulation and apoptosis.

DNA repair genes are responsible for fixing any mutations that occur in the DNA. When these genes become inactivated, the ability of the cell to correct errors in DNA replication diminishes, leading to an accumulation of mutations. This can further contribute to cancer development as the genetic stability of the cell is compromised.

Thus, the inactivation of both tumor-suppressor genes and DNA repair genes creates a permissive environment for the development of malignancy. The correct answer reflects the importance of both gene types in the carcinogenesis process.