The secrets of the shark genome unveiled | Cosmos



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The secret of the success of the great white shark (Carcharodon carcharias) can be in his DNA.

Researchers have revealed that the genome of the great white, whose ancestors evolved 45 million years ago, is one and a half times greater than that of humans. It contains adaptive genetic modifications that could explain the long history of the species, its life span and even its remarkable sense of smell.

Researchers say the shark genome is particularly well suited to staying healthy, given its length and repetition.

"Not only was there a surprisingly large number of genome stability genes that contained these adaptive changes, but there was also an enrichment of many of these genes, highlighting the importance of this genetic adjustment in white shark" says study author Mahmood Shivji, of the Nova Southeastern University (NSU) in Florida, United States.

Details appear in the log PNAS.

Shivji and his colleagues found that the white shark genome had one of the highest proportions of long interlinear nuclear elements (LINEs) found so far in all vertebrates. LINEs are a type of transposons, also called "jumping genes", capable of changing their location and effectively helping to repair the DNA and thus maintain its stability.

"Genome instability is a very important problem in many serious human diseases," says Shivji, "and we now discover that nature has developed clever strategies to maintain genome stability in these large, long-lived sharks. . "

The researchers suggest that it is "the molecular adaptive emphasis on genome stability" in Big White DNA that allows the superior predator to succeed.

"We still have a lot to learn from these wonders of evolution, including potentially useful information for fighting cancer and age-related diseases, and for improving wound healing treatments at home. the man, as we discover how these animals do it, "adds Shivji.

Consumption of shark cartilage, such as that found in their fins, has been touted as an alternative treatment for cancer, as it was once thought that sharks did not have cancer. (As one researcher told the website LiveScience"Even if they did not have cancer, eating shark products would not cure cancer more than me, eating Michael Jordan would make me better at basketball."

As a result, shark hunting has contributed significantly to the decline of many species – including the Great White, which is currently listed as vulnerable on the IUCN Red List.

"The decoding of the white shark genome will also contribute to the conservation of this shark and its sharks, many of which have a rapidly declining population due to overfishing," said co-author, Steven O. Brien, also to NSU.

"The genome data will be an important asset in understanding the dynamics of white shark populations to better conserve this amazing species that has captured the imagination of so many people."

Among the other highlights of genome sequencing, there is evidence that white shark genes offer superior wound healing capabilities and what could be the key to understanding their incredible sense of smell.

Researchers have discovered a large number of vomeronasal type 2 (V2R) genes that could explain why, even with "very few olfactory receptor genes," sharks are able to sense blood in the water.

"Molecular adaptation to wound healing was also evident, with positive selection of the key genes involved in the wound healing process," the researchers write.

Co-author Michael Stanhope adds, "We have discovered enrichments in positive selection and genetic content involving several genes related to some of the most fundamental pathways of healing, including a key gene for blood clotting.

"These adaptations involving wound healing genes may underlie the much vaunted ability of sharks to effectively heal even large wounds."

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