Damaged Chromosomes

[ODorDO]

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Hello everyone, I just ran into a random question while my buddies and I were studying... What will happen to the process of mitosis/meiosis when one of the chromosomes was damaged?

 

[RogueUnicorn]

not really within scope of the mcat... and what do you mean by damage? breakage? basepair mutation?

 

[Thomas Hearns]

Hello everyone, I just ran into a random question while my buddies and I were studying... What will happen to the process of mitosis/meiosis when one of the chromosomes was damaged?

does it say how theyre damaged?

they're trying to see how much you undeerstand about the processes, and what will happen when you take out a certain functioning part.

 

[Charles_Carmichael]

I agree with bleargh that this is not in the scope of the MCAT and if something like this does show up on the MCAT, it won't be a stand-alone and the passage will give you the info you need to answer it.

However, if you just want to know for the sake of knowing, two things could happen depending on how severe the damage is. If the damage/mutation/whatever isn't extensive, a normal cell will stop the cell cycle, repair the damage, and then, proceed through the cell cycle. If the damage is beyond repair, various intrinsic pathways will be activated (an important player is p53) that will arrest the cell cycle and lead to apoptosis. There are several checkpoints in the cell cycle that arrest the cell cycle if DNA damage is sensed. Hope this helps.

 

[RogueUnicorn]

I agree with bleargh that this is not in the scope of the MCAT and if something like this does show up on the MCAT, it won't be a stand-alone and the passage will give you the info you need to answer it.

However, if you just want to know for the sake of knowing, two things could happen depending on how severe the damage is. If the damage/mutation/whatever isn't extensive, a normal cell will stop the cell cycle, repair the damage, and then, proceed through the cell cycle. If the damage is beyond repair, various intrinsic pathways will be activated (an important player is p53) that will arrest the cell cycle and lead to apoptosis. There are several checkpoints in the cell cycle that arrest the cell cycle if DNA damage is sensed. Hope this helps.

once you start mitosis, though, i am not aware of any intrinsic arrest mechanisms... are you? on a diffeerent note, i would guess the question is asking about some sort of breakage involving the centromeres that prevents proper chromatid separation or something.

 

[Charles_Carmichael]

once you start mitosis, though, i am not aware of any intrinsic arrest mechanisms... are you? on a diffeerent note, i would guess the question is asking about some sort of breakage involving the centromeres that prevents proper chromatid separation or something.

Actually, during mitosis, there's a spindle-assembly checkpoint to make sure that there's proper attachment of the spindle microtubules to the chromosomes (the checkpoint components are located on the kinetochores). Also, there's a chromosome segregation checkpoint, which senses the location of segregating chromosomes at the end of anaphase and regulates exit from mitosis.

However, even if a cell with damaged DNA successfully goes through mitosis, this damage will be recognized in the G1 checkpoint and arrests the cell from proceeding through another division. The p53 I mentioned earlier is very critical here and in several other DNA damage checkpoints later on in the cell cycle.

(FYI: On a side note, there's frequently a loss of p53 function in cancer cells. p53 is so critical in regulating the decision to commit to mitosis or not that loss of this protein, which is a tumor suppressor, is the mutation that pushes a lot of tumor cells into full-blown malignancy.)

Hope this helps.