Question

Compare and contrast proto-oncogenes and tumor suppressor genes with respect to modes of action and examples

Answer 1

Comparison and contrast of proto-oncogenes and tumor suppressor genes are as follows:

Proto-oncogenes	Tumor suppressor genes
It is a gene whose gain-of-function mutation drives a cell towards cancer	It is a gene whose loss-of-function mutation drives a cell towards cancer
Mutation of a single copy of a proto-oncogene is sufficient for producing cancerous cell	Mutation of both copies of tumor suppressor gene is required for producing cancerous cell because mutation in this gene is recessive in nature
Proto-oncogene activates growth and divisions of cell and reducing sensitivity to cell death	Tumor suppressor gene inhibits cell growth and division and promote cell death
The protein encoded by this genes are growth factors, growth factor receptors, signal transducers and transcription factors	The protein encoded by this genes are cell cycle progression regulator/ inhibitor, receptor or signals that inhibits cell cycle progression, check point controller, apoptosis promoter and involved in DNA repair
Gene amplification, point mutation, chromosomal translocation and insertional activation of this genes are the main cause of cancerous cell formation	Deletion and point mutation of this genes are the main cause of cancerous cell formation
Mutations take place mainly in somatic cell (not inherited)	Mutations take place both in somatic cell and germ-line cell (inherited).
The examples of proto-oncogene are erbB, K-ras, myc, sis, abl and src etc.	The examples of tumor suppressor gene are p53, Rb, BRCA 1, NF1 and CDK 4 etc.
Very low tissue preference	High tissue preference
Mutation of this genes cause chronic mylogenous leukemia, Burkkitt’s lymphoma, lung cancer and kidney cancer etc,	Mutation of this genes cause colon carcinoma, breast cancer, neurofibromas, retinoblastoma and melanoma etc.