Which cell causes cancer?

Question

Herbie eats excessive amounts of hotdogs each week. They are preserved with sodium nitrite, but his stomach is slowly finding out as it's acid converts the sodium nitrite to nitrous acid, a weak mutagen. In the lining of Herbie's stomach three little cells each experience a mutation in their DNA and it happens to be in the very same gene--a kinase gene called src. (Src is an example of what Dr. Howard Temin called a "proto-oncogene.) But the three little cells each experienced a different kind of mutation in that gene:

Cell #1's src DNA was altered so that it's product is present in normal amounts, but no longer functions.

Cell #2's src DNA was altered so that it produces almost no gene product at all.

Cell #3's src DNA was altered so that it's gene product has normal function but is overproduced.

Which cell is more likely to become cancerous and why?

Answer 1

Cell 3

An oncogene is one that causes cancer. Src is a proto-oncogene, that is, it could potentially cause cancer. If you have too much Src protein present then that could lead to cancer.

On the other hand, if Src were a tumor suppressor (which it isn't) then either cell 1 or cell 2 would be the one to cause cancer.

Answer 2

In order to answer this question, you need to read and learn about the function of the src protein. I'm guessing that this information was presented either in your text or in a lecture about oncogenes and their role in cancer development.

Once you understand the role of the product of the src gene, you'll have no problem answering this question