Mutations across species reveal clues to ageing

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A study suggests that how long animals live is related to how quickly their genetic code changes.

Researchers found that mammals have the same number of changes by the time they die.

The analysis of 16 species shows that short-lived animals burn through their allowance more quickly.

It helps explain why we age and sheds light on one of cancer's most puzzling mysteries.

The findings were thought to be staggering and thought provoking.

The instruction manual for building and running our bodies contains changes to our genes.

It has been known for a long time that those genes are the root of cancer, but whether they are important for aging has been debated for decades. The first experimental evidence suggests they are.

They looked at how quickly different life expectancies change. They looked at the genetics of a cat, dog, ferret, giraffe, horse, human, lion, mouse, naked mole rat, rabbit, rat, ring-tailed lemur and a tiger.

The study showed that mice have an average of 800 mutations a year, which lasts just under four years.

The longer the animals live, the less they change.

A lion 160 and a giraffe 99 are the annual variations of dogs. Humans averaged 47.

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One of the researchers, Dr Alex Cagan, said the pattern was "striking" and that all the animals in the study had at least 3,200 different genes.

We would die with more than 50,000 genetic alterations if people's genes were the same as that of mice.

Despite having different lifespans, the mammals had the same number of mutations at the end of life, according to Dr Cagan.

This is the number, but what does it mean? He said it was a mystery to them.

It could be that the cells in the body reach a critical number of changes. Somecells start to take over critical tissue, such as in the heart, as we age, so organs do not function properly.

It is unlikely that aging is down to a single process inside our cells.

Epigenetic changes are thought to play a role. The question of whether or not there are ways of slowing the genetic damage or even repairing it is posed by this.

The researchers want to know if this pattern holds true for all life or just mammals. They want to add fish to the analysis, including a shark that can live over 400 years old.

There is a question of why big, long-living animals have high rates of cancer.

The more cells you have in your body, the more likely you are to get cancer. This should be bad news for elephants and whales.

Whales have more cells than we do. They shouldn't exist as they would have cancer before they were grown up.

The researchers say that the paradox is not as simple as it seems because big animals tend to live longer.

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Despite being thousands of times larger, Naked mole rats and giraffes live to broadly the same age.

You would expect the giraffe's mutation rate to be even lower, but it's like body size doesn't matter.

The researchers argue that other methods of suppressing cancer must have evolved. Elephants have more copies of a piece of DNA that suppresses tumours.

The difference between a human's 47 mutations a year and a mouse's 800 was huge.

This difference is staggering, given the large overall similarities between human and mouse genomes.

These results are thought- provoking.

Dr Simon Spiro, a wildlife veterinary pathologist at the Zoological Society of London, said that animals live longer in zoos than they do in the wild, so their vets spend a lot of time dealing with old age related conditions.

The genetic changes identified in this study suggest that diseases of old age will be the same across a wide range of mammals.