Large animals mutate slowly


Throughout life, mutations accumulate in our DNA. Cells try to fix them, but over time, more and more mutations, and as a result, they trigger various diseases. The best-known and perhaps the most severe mutational nuisance is cancer, but aging in general is thought to be the result of an accumulation of uncorrected DNA defects. From this we can conclude that in those who live longer, mutations do not accumulate as quickly. And although the hypothesis about the relationship between rapid aging and the rate of accumulation of mutations arose almost in the middle of the last century, it has only been possible to correctly verify it only now.

The best thing here would be to take different types of mammals. Employees Sanger Institute they did just that: together with colleagues from the Zoological Society of London and the German Cancer Research Center, they analyzed mutations in sixteen animal species, including mice, tigers, giraffes, humans, and others. Cells were taken from the intestinal epithelium. There were more than two hundred such samples, and in each case, the researchers read the genome almost completely, and read it so that mutations from different species could be compared with each other.

In an article in Nature it is said that in different species the number of mutations increased linearly and in the same ways. Neither the way of life nor the diet influenced the mechanism of mutations, and there were no special jumps in them. The difference was in speed: in short-lived species, mutations accumulated faster than in long-lived species. That is, if you build the dependence of mutations on time, then for a mouse, and for a person, and for a giraffe, these will be straight lines, only for a mouse the line will be much steeper; and the molecular features of the DNA defects in all three will be very similar.

Another result concerns Peto’s paradox, which we wrote about several times: its essence is that in large animals the probability of oncological diseases should be greater than in small ones. Large animals have more cells, and since tumors arise from mutant cells, it is clear that for those who have more cells, a tumor is more inevitable, so to speak. The paradox is that elephants, for example, get cancer less often than humans. And now new data suggests that the number of mutations depends little on body weight.

That is, say, a giraffe is 40 thousand times larger than a mouse, and a person lives 30 times longer than it – however, the number of mutations with which they come to the end of life differs by about three times.

That is, mutations, firstly, are clearly one of the main factors of aging, and secondly, large animals must have some mechanisms that restrain the accumulation of mutations as their body weight increases. We talked about how elephants manage to avoid cancer and how naked mole rats, which are very small, but live much longer than other animals of the same size, manage to avoid cancer. Perhaps other large animals – giraffes, tigers, bears, etc. – have similar anti-mutation strategies, or perhaps not. In any case, it would be good to know how large animals manage to mutate slowly.


Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.

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