The great white shark is one of the most recognized marine creatures on Earth. This shark possesses notable characteristics, including its massive size (up to 20 feet and 7,000 pounds) and diving to nearly 4,000 foot depths. Great whites are also a big conservation concern given their relatively low numbers in the world’s oceans. In a major scientific step to understand the biology of this iconic apex predator and sharks in general, the entire genome of the white shark has now been decoded in detail.
Decoding the white shark’s genome revealed not only its huge size – one-and-a-half times the size of the human genome – but also a plethora of genetic changes that could be behind the evolutionary success of large-bodied and long-lived sharks. The researchers found striking occur- rences of specific DNA sequence changes indicating molecular adaptation (also known as positive selection) in numerous genes with important roles in maintaining genome stability – the genetic defense mechanisms that counteract the accumulation of damage to a species’ DNA, thereby preserving the integrity of the genome.
These adaptive sequence changes were found in genes intimately tied to DNA repair, DNA damage response, and DNA damage tolerance, among other genes. The opposite phenomenon, genome instability, which results from accumulated DNA damage, is well known to predispose humans to numerous cancers and age-related diseases. The findings are reported in the ‘Latest Articles’ section of the journal Proceedings of the National Academy of Sciences, USA.
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