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Mutation and proto-oncogenes

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nfg05

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Which of the following is NOT a characteristic of an oncogene?
A. A mutation causes it to gain a new function.
B. A mutation changes it to a proto-oncogene

Those are the two answers I was between, and the answer is supposedly B.

As I understand it, a proto-oncogene is a gene that, if mutated, causes cancer. This type of mutation is classified as a gain of function mutation.

So it makes sense to me that an oncogene could back-mutate and go back to a proto-oncogene, while a mutation to an oncogene would likely cause is to lose a function, not gain a new one, making A the better answer to the question. Anyone care to provide some explanation?
 

seraph524

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Whoa...first of all, I think that is a very bad question overall...

If you ask me, in my opinion, I think both possibilities are possible. It is possible for an oncogene to have mutations that can enhance its functions, but also (if you are lucky enough) to have it "mutate" back into a proto-oncogene. However, given that most proto-oncogenes require multiple mutations in order to become an oncogene in the first place, it is more likely that a single mutation will add functions rather than revert it back to its proto-oncogene state.

Also, I think a third possible choice could be a loss of function. What if the oncogene has a mutation in a critical catalytic residue? That would almost certainly inhibit its function.
 

ThePandaFactor

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the answer's B, proto-oncogene is just a gene that often develops cancerous mutations (like ras genes), once mutated it is definitely not characteristic to have to randomly just revert back, I doubt that's even happened since oncogene mutations mess them up basically completely. Also even if it did I don't know you'd say that it changed back into a proto-oncogene.
 
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