Mitochondrial DNA and the molecular clock, Douglas Wallace
Interviewee: Douglas Wallace. Geneticist Douglas Wallace explains a method of mapping a population's history using the mutations accumulated by its members. (DNAi Location: Applications > Human origins > Gene genealogy > A molecular clock? > the molecular clock)
The molecular clock basically is the simple concept that mutations accumulate in a piece of DNA at a roughly constant rate because they occur by chance. Therefore if you have a individual who then has children who have children who have children, over that time as generations move outward, there is a certain probability with each generation that a new mutation will occur, in that piece of DNA. So if you know the rough rate that those mutations occur by chance, then at some later time you can look at the DNA of the descendant from individual of line A and the descendant of line B, and examine the number of changes in their mitochondrial DNAs, or nuclear DNAs, compare them, and the number of changes will be roughly proportional to the time that they shared a common ancestor. So in fact than, by sequencing the mitochondrial DNA of a large number of people around the world, what we've been able to do is exactly determine the relative amount of time that it's been since each of them shared a common mother because we're using mitochondrial DNA. So you can then reconstruct the maternal ancestry of all the people around the world by simply comparing the number of ticks on the molecular clock, that is the number of mutations between any two pieces of mitochondrial DNA.
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Molecular geneticist Douglas Wallace talks about the way mitochondrial DNA is inherited.
Molecular geneticist Douglas Wallace talks about the origin of our mitochondria and the DNA within.
Geneticist Mark Stoneking speaks about the findings of early mitochondrial DNA studies.
Geneticist Mark Stoneking, one of the authors of a controversial 1987 paper on mtDNA, talks about our common female ancestor.
This illustration shows the two major mitochondrial DNA lineages. The lower branch includes only African populations. The upper branch has both African and non-African members.
Mitochondrial DNA pioneer Douglas Wallace speaks about the movement of different populations out of Africa.
Mitochondrial DNA research pioneer Douglas Wallace speaks about mitochondrial DNA and theories of human evolution.
Mutations and the molecular clock.
Geneticist Mark Stoneking talks about the difficulties of measuring time by mutations.
Mitochondrial DNA research pioneer Douglas Wallace speaks about the populations he samples and the direct application of the research.