Definition of Oncogenes, Proto-oncogenes,
& Tumor Suppressor Genes

Oncogenes

Oncogenes are mutated genes that are resident in cellular chromosomes. These are genes whose action positively promotes cell proliferation. The normal non-mutant versions are properly called proto-oncogenes. The mutant versions are excessively or inappropriately active.

 

Proto-oncogenes

Segments of DNA, originally responsible for cell growth and proliferation, which remain dormant until activated.

• Over 50 such segments currently identified.
• Cellular oncogenes, "c-onc" have 3 letter code.
• Chromosomal location known for many human oncogenes.
• Often produce a protein product - enzyme with regulatory activity.
  

Tumor suppressor genes

Tumor suppressor gene products inhibit cell proliferation. Mutant versions in cancer cells have lost their function.