Hello. My name is Toomas Kivisild and I'm
a human geneticist working in the Department of Human Genetics at KU Leuven.
This talk is about evolution of human mitochondrial DNA variation.
To talk about the origin of mitochondria in our cells,
we need to go back in time more than
two billion years to the origin of life on Earth,
and the first split into two major domains,
the bacteria and the archaea.
It is only after these two domains had evolved that
our eukaryotic origins emerged as a merger between the archaea and the bacteria.
We have inherited our nuclear genes predominantly from our archaeal ancestors,
and we have got our mitochondria from
a specific branch of the bacteria, the alpha purple bacteria,
so that our cells contain these two distinct forms of life.
The mitochondria in our cells are very important.
They're important for the energetic purposes of our cells,
and they have enabled the eukaryotic organisms to diversify in cell type and cell size.
During these two billion years since the origins of eukaryotes,
there has been an ongoing process of transfer of mitochondrial genes to the nucleus.
As a reminder of these two distinct origins,
there are differences in the code.
For example, in the mitochondrial DNA,
the TGA codon means tryptophan,
whereas in the nuclear language it means a stop code.
When we look at each cell of a eukaryote,