New paper out on the genome of the giant lungfish. I've not had time yet to read the whole thing, but thought i'd share it ahead of that because it's very significant for two reasons:
One is that lungfish, as part of the lobe-finned fishes, have been proposed to be the closest living species to tetrapods. The fossil record here, including famed intermediates like Tiktaalik, is pretty clear. The genome gives us the chance to test whether the present day evidence is consistent with the fossil record. In news that shouldn't surprise anyone, it is: "Phylogenomic analyses ascertained that lungfish occupy an evolutionary key-position as closest living relatives to tetrapods." They also see some indications of things that would be adaptive for tetrapods pre-existing their split from lobe-finned fishes. These included a limb-like pattern of homeobox gene expression, additional copies of genes associated with air breathing, and more odorant receptors that work in air.
The second thing is an oddity that's specific to lungfish: their genomes are enormous. This genome is 17x the size of the human genome, and there's no obvious (or even unobvious) explanation for why that extra DNA is needed. Well, we now know where it comes from: mobile genetic parasites are still active in the genome, and most of the extra DNA is simply copies of these parasites inserted between genes and within the introns that are deleted from mature RNAs. This is exactly the sort of thing we'd expect to see if we treat junk DNA as a scientific hypothesis and derive predictions from it.
May have more once i read the paper, but it's open access, so anyone can have a look for themselves.
https://www.nature.com/articles/s41586-021-03198-8
One is that lungfish, as part of the lobe-finned fishes, have been proposed to be the closest living species to tetrapods. The fossil record here, including famed intermediates like Tiktaalik, is pretty clear. The genome gives us the chance to test whether the present day evidence is consistent with the fossil record. In news that shouldn't surprise anyone, it is: "Phylogenomic analyses ascertained that lungfish occupy an evolutionary key-position as closest living relatives to tetrapods." They also see some indications of things that would be adaptive for tetrapods pre-existing their split from lobe-finned fishes. These included a limb-like pattern of homeobox gene expression, additional copies of genes associated with air breathing, and more odorant receptors that work in air.
The second thing is an oddity that's specific to lungfish: their genomes are enormous. This genome is 17x the size of the human genome, and there's no obvious (or even unobvious) explanation for why that extra DNA is needed. Well, we now know where it comes from: mobile genetic parasites are still active in the genome, and most of the extra DNA is simply copies of these parasites inserted between genes and within the introns that are deleted from mature RNAs. This is exactly the sort of thing we'd expect to see if we treat junk DNA as a scientific hypothesis and derive predictions from it.
May have more once i read the paper, but it's open access, so anyone can have a look for themselves.
https://www.nature.com/articles/s41586-021-03198-8
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