Say whether each change is a gain of function of an oncogene (an accelerator stuck on) or a loss of…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say whether each change is a gain of function of an oncogene (an accelerator stuck on) or a loss of function of a tumour suppressor gene (a brake cut).
- A mutation makes a growth factor receptor send a signal even when there is no growth factor.
- A mutation destroys the gene for p53.
- A mutation changes Rb so that it can no longer bind E2F.
- A mutation makes a cell produce a cyclin all the time.
- A viral protein binds p53 and switches it off.
Need a reminder? The key ideaShow
Cancer cells ignore the checkpoints. A proto-oncogene codes for an accelerator of the cycle, and a mutation can turn it into an oncogene (a gain of function). A tumour suppressor gene such as that for Rb or p53 codes for a brake, and a mutation can cut it (a loss of function). A tumour that doubles its cells every days needs doublings to reach cells.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Oncogene. It is a gain of function.
Step 2. (b) Tumour suppressor lost. It is a loss of function.
Step 3. (c) Tumour suppressor lost. Rb can no longer hold E2F, so the brake is cut.
Step 4. (d) Oncogene. The accelerator is on all the time.
Step 5. (e) Tumour suppressor lost. The effect is the same as a loss of p53.
Answer: (a) oncogene; (b) loss; (c) loss; (d) oncogene; (e) loss.
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