Question

mutations in the kras gene are frequently found in colon cancer. these mutations are always missense mutations (snps that result in a different amino acid), primarily in codons 12 or 61. mutations in the apc gene are also associated with colon cancer. in this case, however, nonsense (snps that result in a stop codon) and frameshift (insertion/deletion) mutations are most common and are scattered throughout most of the coding region. based on this: (a) is kras more likely an oncogene or a tumor-suppressor gene? why? (b) is apc more likely an oncogene or a tumor-suppressor gene? why?

Answer 1

The KRAS gene is considered an oncogene because its mutations are missense and lead to a functional change in the protein, while the APC gene is regarded as a tumor-suppressor gene because its mutations result in nonfunctional or truncated proteins.

Step-by-step explanation:

KRAS Gene and Oncogene Versus Tumor-Suppressor Gene

Based on the information provided, the KRAS gene is more likely an oncogene. This is inferred from the fact that the mutations associated with KRAS in colon cancer are usually missense mutations leading to the production of a differently functioning protein, which is characteristic of oncogenes that have gain-of-function mutations. Oncogenes can cause the malignant phenotype of cancer cells by promoting unregulated cell proliferation or inhibiting apoptosis.

On the other hand, the APC gene is more likely a tumor-suppressor gene. APC gene mutations in colon cancer are generally nonsense or frameshift mutations, which tend to produce nonfunctional or truncated proteins that lose their ability to regulate the cell cycle. This loss of function is typical for tumor-suppressor genes, which normally work to inhibit cell division and promote repair mechanisms to prevent cancer.