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posted by martyb on Saturday May 24 2014, @09:27AM   Printer-friendly
from the happened-twice-it-was-so-nice dept.

If you think that early animals started out simple and gradually evolved new features, and things like sponges branched off before the new features were added, you wouldn't be alone. Over the years, lots of researchers argued the same thing. But a recent genome sequence indicated that the oldest branch of the animal family tree that led to the comb jellies, with muscles, nerves, and tentacles, were an older branch than sponges. Now with a new paper on the comb jelly, researchers are starting to argue over what this actually tells us about the earliest animals.

The comb jellies' genome contains a variety of other indications that they are exceptional. Most of the innate immune system, which broadly recognizes pathogens like bacteria and viruses, is missing. So is the machinery that processes micro RNAs, which are used to control the expression of other genes. Key regulators of development, like hedgehog and JAK/STAT proteins, are also absent. So are key genes involved in the formation of muscles, suggesting that these, too, may have evolved separately in the ctenophores.

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  • (Score: 2) by Joe on Saturday May 24 2014, @09:52PM

    by Joe (2583) on Saturday May 24 2014, @09:52PM (#47188)

    As far as I know the main reasons why all life contains DNA are: it is great at storing information, it is structured in a way that enables faithful replication, and it is very stable. RNA is very close, but it fails to compete with DNA when it comes to stability. This is one of the reasons that RNA has an upper-cutoff of around 30,000nts in length (Coronaviruses, such as SARS and MERS, have RNA genomes in this range).

    The question really depends on your definition of life: DNA is obvious since all cellular life uses it, RNA can be used as viral genomes, and amino acids (that make-up proteins) can maintain structural information and prions can propagate that information.

    - Joe

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  • (Score: 2) by frojack on Saturday May 24 2014, @11:46PM

    by frojack (1554) Subscriber Badge on Saturday May 24 2014, @11:46PM (#47205) Journal

    You are still thinking inside the box.

    If DNA wasn't good at its job, we probably wouldn't be here.

    But there is no reason to assume it is the ONLY mechanism that could provide the same functionality.

    No, you are mistaken. I've always had this sig.