Question

What are oncogenes? How were tumor retroviruses used to discover oncogenes? What are tumor suppressors? What are the differences between tumor suppressors and oncogenes? How does p53 function to induce cell cycle arrest and apoptosis in response to stress?

Answer 1

Oncogenes are specific fragments of DNA/genes with a capability to produce cancer in an organism, often due to mutation in these gene, they become hyper-expressive and cause cancer.

Oncogenes are first of all discovered in RNA viruses’ a.k.a retroviruses as they have potential to reverse transcription, DNA from RNA through and why this mechanism they can integrate with host (human) genome and cause deadly diseases like cancer.

Normally we don't get cancer even after exposure to oncogene due to p53 gene, which is tumor suppressor gene and inhibit the oncogene expression and prevent cancer formation. In case of actively functioned tumor suppressor gene it suppress the activity of oncogene so that they cannot cause cancer, if tumor suppressor gene is not working properly (switch off) then it way induce cancers.

Under normal condition, p53 gene maintain the equilibrium and nullify activity of various mutagenic, carcinogenic or oncogenic agents through cope up with cell stress due to endogenous or exogenous sources. It arrest the cell cycle when activated for the repair of the DNA bases if damaged, if unable to repair then induce apoptosis for removal of the damaged cell through extrinsic or intrinsic pathways(s).