Scientists have sequenced the largest known animal genome, which is 30 times larger than the human genome.
The genome belongs to a South American lungfish (Lepidocerin Paradoxprimitive, air breathing Fish Fish “jump” from water onto land using strange, limb-like fins. Researchers have found that the fish’s DNA has expanded dramatically over the past 100 million years of evolutionary history, accumulating the equivalent of one human genome every 10 million years.
These findings may help shed light on how genomes expanded across the tree of life.
Lungfish are sometimes called “living fossils” because they have been around for hundreds of millions of years. They are thought to be Species most closely related to the first tetrapodsthe ancestor of all vertebrates. These ancestors likely grew limbs and crawled on land about 370 million years ago during the Devonian period (419 million to 359 million years ago), Science mentioned.
Previously, scientists have sequenced the genomes of other lungfish species, including the Australian lungfish (Neoceratodus foresteri). Next on the list was the African lungfish (Protopterus anectinus) and (L. Paradoxa), whose genome is twice the size of its air-breathing relatives from other continents.
The team described the genome of the South American lungfish on August 14 in the journal natureIt turns out that these air-breathing fish carry up to 91 billion base pairs, or letters, of DNA in their genomes.
That’s enough letters to fill 100,000 books. However, only 20,000 genes encode proteins, meaning the rest are likely mostly junk, the study found. More than 90 percent of genetic material is made up of Movable items (TEs), or highly repetitive “jumping” genes that have been copied from elsewhere in the genome.
Scientists have also identified the cause. Lungfish genomes have expanded dramatically over the past 100 million years. South American lungfish have been shown to have key genes that suppress antiviral effects, which the organisms may have inherited from viruses long ago.
Carrying too much genetic baggage can be a problem.
“That must be a huge cost to the animal.” Axel Mayeran evolutionary biologist at the University of Konstanz, He told Science magazine“All but one of the chromosomes in this lungfish are about the size of the entire human genome, so copying this DNA requires a lot of energy. The nucleus and the cell it encases must be even larger.”
On the other hand, the extra DNA could be useful when animals need to adapt to changing environments, Meyer said. That’s because the genetic elements can increase or decrease the expression of genes, allowing for faster adaptation.
While the lungfish may hold the record for the largest known animal genome, it does not have the largest genome ever. That honor goes to Strange fern has 160 billion letters in its genome – More than 50 times more letters than are found in human cells.
This lungfish may not hold the record for the largest animal genome for long. The marbled lungfish (Protopterus aethiopicus) It may have a genome 50% larger than this, Klaus Peter Stelzer“Of course, this species would need to have its genome sequenced before this could be confirmed,” an evolutionary biologist at the University of Innsbruck in Austria who was not involved in the study told Science.
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