Brainstorm how you think mutations occur in proto-oncogenes and tumor suppressor genes that can lead to cancer.

Mutations in proto Oncogenes make it an oncogene and mutation in Tumour suppressor gene makes proteins which cannot stop a cell division. Both of these reasons lead to cancer.

A proto oncogene is present in each an every cell of a human. Now the proto Oncogenes code for the proteins that help in cellular growth. A mutation in this gene lead to uncontrolled secretion of proteins that initiate uncontrolled cellular growth. This causes cancer.

A Tumour suppressor gene codes for proteins that help in checking the cell division when there is a contact with nearby cell. This phenomenon is called contact inhibition. Now as this gene is mutated, the protein that is produced is defective and is unable to control the cell division when there is contact with nearby cell. Thus, this uncontrolled cell growth leads to cancer.