mtDNA, QUICK QUESTION PLEASE HELP

[spherelin]

Okay, I'm really confused?
I'm hearing that mtDNA mutates quickly - quicker than nDNA...
but then some commercial papers think otherwise (their answers indicate that it doesn't)...
so does it?

Thanks everyone!

[Jenny_2108]

Okay, I'm really confused?
I'm hearing that mtDNA mutates quickly - quicker than nDNA...
but then some commercial papers think otherwise (their answers indicate that it doesn't)...
so does it?

Thanks everyone!

LOL this ques was asked on Douchy's page
Here's his ans

"That's not an easy question to answer. (they asked it on the exam a couple of years ago - but then gave everyone a mark). The answer is a bit complex. Firstly, it needs to be said that some regions of DNA mutate faster than others even within a single chromosome. That said, overall, the rate of mutation is higher in mtDNA because there is no proof-reading enzyme in mitochondria. (this is also true of prokaryotes) so mistakes during replication are more likely to go unchecked. BUT there are also no introns in mtDNA, so mutations that occur are more likely to have a negative impact on function, and will be removed by purifying selection. So basically, it all depends on which part of the DNA you are comparing. If you just compare non-coding sequences, then mtDNA accumulates mutations faster but if you just compare coding sequences, then chromosomal DNA accumulates mutations faster. On average, mutations happen at a higher rate in mtDNA but changes accumulate faster in chromosomal DNA. But even that is controversial - as different regions of coding DNA (for example) seem to mutate faster than others.

I could be wrong... i frequently am... when I make predictions, but I would be a little surprised if an exam question expected you to say which has the higher mutation rate - because they got in trouble last time they tried to ask that. lol. If they did as such a thing, I think they would phrase the question very very carefully ... so that it was not ambiguous like last time" (Douchy)

[spherelin]

Okay, I'm really confused?
I'm hearing that mtDNA mutates quickly - quicker than nDNA...
but then some commercial papers think otherwise (their answers indicate that it doesn't)...
so does it?

Thanks everyone!

LOL this ques was asked on Douchy's page
Here's his ans

"That's not an easy question to answer. (they asked it on the exam a couple of years ago - but then gave everyone a mark). The answer is a bit complex. Firstly, it needs to be said that some regions of DNA mutate faster than others even within a single chromosome. That said, overall, the rate of mutation is higher in mtDNA because there is no proof-reading enzyme in mitochondria. (this is also true of prokaryotes) so mistakes during replication are more likely to go unchecked. BUT there are also no introns in mtDNA, so mutations that occur are more likely to have a negative impact on function, and will be removed by purifying selection. So basically, it all depends on which part of the DNA you are comparing. If you just compare non-coding sequences, then mtDNA accumulates mutations faster but if you just compare coding sequences, then chromosomal DNA accumulates mutations faster. On average, mutations happen at a higher rate in mtDNA but changes accumulate faster in chromosomal DNA. But even that is controversial - as different regions of coding DNA (for example) seem to mutate faster than others.

I could be wrong... i frequently am... when I make predictions, but I would be a little surprised if an exam question expected you to say which has the higher mutation rate - because they got in trouble last time they tried to ask that. lol. If they did as such a thing, I think they would phrase the question very very carefully ... so that it was not ambiguous like last time" (Douchy)

Thanks for that. Do you think that if VCAA asked for the positives of using mtDNA, i should just stick to the idea that it does not undergo recombination and is passed down the maternal line?
Also, do these positives just enable a more efficient/accurate way of determining evolutionary relationships?
Thanks!!!!