Oncogenes

• Most oncogenes are mutations of proto-oncogenes. Proto-oncogenes stimulate a cell to divide when growth factors attach to a protein receptors on its cell-surface membrane. This then activates the genes that cause DNA to replicate and the cell to divide.
• If a proto-oncogene mutates into an oncogene, it can become permanently activated for two reasons : the receptor protein on the cell-surface membrane can be permanently activated, so cell division is constantly switched on, OR, the oncogene may code for a growth factor that is then produced in excessive amounts, stimulating excessive cell division.
• If an oncogene becomes permanently activated, the body cells will divide too rapidly and out of control, causing a tumour/cancer to develop.
• Most cancer-causing mutations associated with oncogenes are acquired, not inherited.