Why do unrelated cheetahs have the same DNA?

The cheetah has had a tough time in the last 12,000 years or so.

 

A mass extinction around 12,000 years ago saw Earth lose an estimated 75% of large mammals. Never to be seen again. Following this, only a handful of cheetahs survived. Great news! Sort of. With only a small number of cheetahs remaining, it was up to these select few to pass on their genes and continue the species, which they did very efficiently. However, the results of inbreeding have had a significant impact that can still be seen today.

Today you could analyse the DNA of two seemingly unrelated cheetahs and get results showing they may as well be twins. When looking at two unrelated cheetahs they actually share about 99% of their genes. In other species this figure is usually only around 80%.

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If the number of cheetahs worldwide keeps decreasing, the problem of inbreeding will only increase.

 

It doesn’t seem like a huge problem, cheetahs are happily going about their lives. And they still exist (despite other pressures such as habitat loss and hunting). However, sharing so many of their genes can have serious problems for the future. As a species, low genetic diversity can make cheetahs less adaptable, and more susceptible to disease. All it could take is one strain of disease to kill of an entire population. The lack of genes in the gene pool also lead to birth defects, and any potentially harmful mutant genes which would usually occur in the background, now have a higher chance of being expressed.

The result of this inbreeding can be seen through skin grafts. Two unrelated cheetahs are able to donate skin (and possibly organs) to other cheetahs without fear of rejection. A problem which is common in human transplant recipients.

The case of the cheetah is a really interesting one. Low genetic diversity has always been considered a major problem and one that must be avoided at all costs. Hence why zoos continually move animals around the world between organisations – to keep the gene pool varied. Studying the cheetah could help scientists determine a threshold for how much genetic diversity needs to be lost before a species faces extinction.