Genetics/Cancers

Readings

• Study guide:
• Wikipedia article: Oncogenes

Dominant Mutations in Oncogenes

Dominant mutations in oncogenes usually disrupt or constitutively activate signaling pathways that inform the cell about its environment. A mutation in an oncogene protein or a large excess of the normal protein makes it insensitive to upstream members of the pathway, which leads to constitutive activation of the pathway and unrestrained proliferation. These mutations are usually not inherited and arise during somatic growth.

Oncogenes can also be activated by insertion of a retrovirus at a nearby chromosome location.

Recessive Mutations

Tumor Suppressor Genes

Tumor suppressor gene mutations are mutations in signaling pathways or cell cycle progression which regulate cell cycle production. This type of cancer appears to be inherited as a dominant trait even though the original mutant is recessive.

p53 Mutations

P53 is a tumor suppressor gene. P53 functions as a checkpoint to prevent commitment to S phase if there is unrepaired DNA damage. If there is unrepaired damage, p53 activates production of the p21 gene and this prevents the cyclin/cdk complex from initiating S. If the damage remains unrepaired, p53 causes apoptosis in the cell, eliminating potential mutagenic effects.