Question

Explain why a gain-of-function mutation to a proto-oncogene (or its promoter) may be associated with increased risk of cancer. (b) Explain why a loss-of-function mutation to a tumor suppressor gene may be associated with increased risk of cancer.

Answer 1

a)proto-oncogene are the genes which promote in the cell division or prevents cell death so when such genes or it`s promoter is mutated such that it`s expression increase it will increase the risk of cancer because the cells will divide more and more or cell will not undergo apoptosis. these type of mutations which increases it`s expression make protooncogene an oncogene. Increased cell division and no cell death leads to cancer.

b) tumour suppressor genes are those genes which control cell growth or genes which induce apoptosis when these genes are mutated such that it losses it`s function there will be no control over cell growth so cells divide more and more leading to cancer so loss of function mutations in tumour suppressor gene may be associated with increased risk of cancer, there are many other factors controlling cell division so loss of function mutation in tumour suppressor genes increases the chance or cancer.