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MCAT Content / Biosignalling / Oncogenes Apoptosis

Oncogenes, apoptosis

Topic: Biosignalling

Oncogenes are genes that cause cancer when mutated and apoptosis is programmed cell death.

The genes that code for the positive cell cycle regulators are called proto-oncogenes. Proto-oncogenes are normal genes that, when mutated in specific ways, become oncogenes: genes that contribute to a cell to becoming cancerous. There are many ways for this to happen. For example, a mutation can cause a change in the function, location, expression, or activation of a protein.

If the cell cannot reproduce with the oncogene mutation, it will not propagate to future daughter cells. However, if the mutation can be passed on, subsequent daughter cells may acquire even more mutations that will be increasingly detrimental.

Apoptosis is programmed cell death, a normal process that destroys cells no longer needed by the body. Apoptosis allows a cell to die in a controlled manner that prevents the release of potentially damaging molecules from inside the cell and allows cellular material to be recycled. Many checkpoints monitor a cell’s health, and if abnormalities are observed, a cell can initiate the process of apoptosis. However, in some cases, such as a viral infection or uncontrolled cell division due to cancer, the cell’s normal checks and balances fail. External signalling can also initiate apoptosis.


Practice Questions


MCAT Official Prep (AAMC)

Practice Exam 4 B/B Section Passage 6 Question 34

Key Points

• Proto-oncogenes are normal genes that regulate the cell cycle and become oncogenes when mutated.

• Oncogenes contribute to a cell becoming cancerous through a variety of pathways.

• Apoptosis is normal, programmed cell death. It can be disturbed by factors such as viral infection and cancer.

Key Terms

Proto-oncogene: a gene that positively regulates the cell cycle; becomes an oncogene after mutation

Oncogene: a gene that contributes to cancerous cell conversion when mutated or expressed at high levels

Apoptosis: normal programmed cell death

Gene: a section of DNA coding for a protein

Mutation: a change to the base sequence of DNA which is not intended

Daughter cells: the genetically identical cells produced from mitosis of parent cells

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