Oncogenes and proto-oncogenes

Proto-oncogene is a normal gene that have many different functions in the cell. Some proto-oncogenes provide signals that lead to cell division. Other proto-oncogenes regulate programmed cell death (apoptosis). Apoptosis leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells.

When a proto-oncogene becomes mutilated it becomes a oncogene. This causes the cell to divide in an unregulated manner. An oncogene may contribute to the growth of a tumor, which may be cancerous.

Occasionally, however, a gene mutation causes a change that increases the activity of a positive regulator. For example, a mutation that allows the Cdk gene to be activated without being partnered with cyclin could push the cell cycle past a checkpoint before all of the required conditions are met. If the resulting daughter cells are too damaged to undergo further cell divisions, the mutation would not be propagated and no harm would come to the organism. However, if the atypical daughter cells are able to undergo further cell divisions, subsequent generations of cells will probably accumulate even more mutations, some possibly in additional genes that regulate the cell cycle.

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