Friday, April 29, 2016

Cheetah Genome Reveals Low Genetic Diversity

It goes without saying that genetic diversity is necessary for a species to survive in the long run. Genetic diversity in a large population greatly increases the chance of survival for many different events, like disease or a new predator introduced in the area. Also, with a high amount of genetic diversity, unfavorable genotypic and phenotypic traits can be 'weeded out' from generation to generation, increasing a species' survival.

Recently, the entire genome of Acinonyx jubatus (African cheetah) was sequenced by Dobrynin et al. in 2015, which reveals some surprising (and unfortunate) results. Of the approximate 30 mammals that have had their genome sequenced to date, the cheetah has the lowest amount of genetic diversity - lower than other wild cats, and even inbred domesticated dogs and cats. From an evolutionary standpoint this makes sense - cheetahs have been around for approximately 3 million years, and fossil records show at least two different periods (bottlenecks) where cheetahs were forced to interbreed in order to survive. The first period occurred about 100,000 years ago, and the second during the Pleistocene epoch. Due to these small populations breeding with each other, many of the same genotypic and phenotypic frequencies would carry onto subsequent generations, severely lowering genetic diversity in the long run.



This might not be such a big deal, except there are only around 10,000 cheetahs left in the world (and in captivity). In an experimental attempt to determine the amount of diversity within the species, scientists did skin grafts on several cheetahs, and none were rejected. The way Dobrynin and his other colleagues analyzed their genetic diversity was through use of SNVs, or single nucleotide variations. Compared to the genomes of domesticated cats, cheetahs are (on average) 95% homozygous, while domesticated cats are about 24%.


I hope this doesn't foreshadow the extinction of this species in the near future. Unfortunately, because African cheetahs are so genetically similar to one another, a newly introduced disease could easily wipe out the entire species if preventative action is not taken. In order to avoid extinction of this species, selective breeding/outbreeding should definitely be considered. This type of action has been used with the Florida panther (which is also very endangered), and so far it's been working. If the number of cheetahs continues to decline, biological effects like genetic drift or bottlenecks can have a drastic effect on the population (disease as well). With the right steps taken, the cheetah will not become just another extinct species.


Original article: http://www.nytimes.com/2016/03/01/science/in-dna-clues-to-the-cheetahs-speed-and-hurdles.html?_r=0

4 comments:

  1. This makes so much sense, since the cheetahs have been inbreeding due to their small population size there isn't enough diversity in their gene pool to have a variation in their genome to be able to withstand a disease that a species with a diverse genome could withstand.

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  2. Do you think it would be possible to increase the genetic variation by separating the populations of cheetahs from each other for a period of time and then after a few generations reintroduce the two separate populations back together? It may be difficult depending on how fast they are able to reproduce and how large a litter would be.

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  3. Do you think it would be possible to increase the genetic variation by separating the populations of cheetahs from each other for a period of time and then after a few generations reintroduce the two separate populations back together? It may be difficult depending on how fast they are able to reproduce and how large a litter would be.

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  4. The inbreeding among cheetahs makes sense due to the bottleneck effect. I was not surprised at all that cheetahs have the lowest genetic variation of the mammals' genomes that has been tested. I think that scientists need to take action in order to protect the species from extinction. Introducing new members to a population or separating the current population could add genetic variation. If no actions are taken, then a simple virus or bacteria outbreak could wipe out the entire species.

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