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?
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.
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.
NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators.
Argonne National Laboratory, Division of Educational Programs, Andrew Skipor, Ph.D., Interim Division Director.