Nick Lane

It's a process called Muller's ratchet, but it's basically, these mutations are kind of somewhat screened from selection by being compensated for by clean copies that you have of other copies.

So how do you get rid of those mutations that are building up over time?

Well, the answer is what you need to do is increase variants of mitochondrial genes.

What you need to do is effectively segregate into these cells all the mutants and into those ones all the wild-type ones.

Yeah.

So you can do that by multiple rounds of cell division, but it helps if you've got two sexes that effectively only one sex passes on the mitochondria.

So you're already sampling.

So you're already increasing the variance and you're increasing visibility to selection.

So basically it's about the quality of mitochondrial genes.

So we're talking about variance between cells.

So if you imagine that you have 100 cells and they all come from the same parent, let's say, and you randomly give each cell, if you give all the mitochondria that you have kind of straight into a single cell without changing any of the ratios there,

then it's exactly the same as you are.

It's fully clonal.

But if you give, if you take a small subsection of those and you say you take a random 10%, you give 10% to this one, a random 10% to that one, a random 10% to this one, randomly, this cell is going to happen to have got all the good copies.

Yeah.

And this cell is going to happen to have got all the bad copies.

And now you subject these 100 cells to selection and say, how are you doing?

And the one that got all the good copies, that does well, that gets on.

So what you're doing is increasing the variance between this kind of next generation of cells.

So the ones that got all the mutants, they get hit.