Ask A Scientist Molecular Biology Archive

name         Tor
status   student
age           20s

Question -   Since the mitochondria DNA  is inherited entirely from
your mother, would my mitochondric DNA be the  same as my great
grandmothers? How does this DNA change?
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Mutations in DNA occur at random.  Usually there has to be some  mutagen (ie. 
radioactivity, UV rays) or a mistake in copying in just the right  place to 
cause a mutation.  This doesn't necessarily happen at a regular  rate.  But we 
can say that over a very long period of time, say a million  years, or 
100,000, or 10,000 years) a certain number of mutations are likely to  have happened. 
 The longer period of time between two sequences of DNA that  are being 
compared, the greater likelihood there is that a mutation will have  happened.  So, 
if you compare Neanderthal DNA to modern human DNA you see  about 20 
differences on average.  Between any two unrelated modern humans  there are about 6-8. 
 But mitochondrial DNA passes intact between mother  and child.  So your 
grandmother should have gotten her mtDNA intact from  her mother (your 
great-grandmother).  And so on.  It is unlikely that  in that small amount of time a 
mutation will have occurred mathematically  speaking.  COULD it have happened?  
Sure.  But it isn't  likely.  
 
K VanHoeck
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Assuming no mutation, yes. I don't know what the mutation rate of mitochodrial DNA is, 
but I would "guesstimate" that about one in 1,000 individuals would carry a newly 
arising mutation when compared compared to their mother. You might try doing a search 
on Google for "mitochondrial DNA mutation rate".

Ron Baker, Ph.D.
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