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Researchers study why many life forms discard pieces of their DNA as they develop


Because the phenomenon is quite common, they are looking for a selective advantage:

A surprisingly wide array of creatures, all the way up to some vertebrates, dump significant stretches of DNA during early development, so the stretches don’t end up in most of their body cells.

To date, scientists have observed the phenomenon in various insects, in lampreys and hagfish, in hairy one-celled life forms called ciliates, in parasitic roundworms and tiny crustaceans called copepods. They’ve seen it in rat-like marsupials called bandicoots and in songbirds — probably all songbirds, according to recent work. And they expect to find many more cases.

Alla Katsnelson, “The curious case of the shrinking genome” at Knowable Magazine (October 21, 2021)

The reproductive cells retain all of their genes and the retained genes in other cells are all active. Thus, one hypothesis is that discarding is a way of preventing inactive genes from hanging around and causing trouble. But then, why don’t these life forms use gene silencing tags, as other life forms do?

Another weird thing researchers discovered is that the fungus gnat has an extra genome, apparently that of another species, inside its germ cells.

Overall, it’s not nearly as simple as we might have expected.

Very interesting article that leaves you scratching your head. As I scratch my head, I wonder if what is seen here is related to a view I've been coming to over the last year or so: namely, that DNA is a storage device that RNA uses, with RNA being the real driver of life processes. When you consider all the different sized, differently-functioning RNAs that are out there, and further consider that it is an RNA molecule that is responsible for fertilization (or so I read a few years back), I think it makes more sense to think of RNA directing DNA to do what RNA needs to do to keep organisms alive. Without further elaboration, what might be happening here is that the later deleted chromosomes contain important ncDNA which, when translated into RNA molecules, continue to exist in the body cells through normal cell division (passed on from one generation to the next), so that these 'large' chromosomes are no longer crucial to life being sustained once the embryo reaches some size, and so, are deleted (one has to consider that the use of these ncDNA molecules could interfere with the normal cell machinery and so become dangerous--an idea that some of these authors propose as the reason for these wholesale deletions). In any event, just some thoughts.PaV
October 23, 2021
12:23 PM

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