StemCell Therapy

Modern biology relies on relatively homogeneous building blocks to encode genetic information, said Seohyun Kim, a postdoctoral researcher in chemistry and first author on the paper. If Szostak and Kim are right and Frankenstein molecules came first, why did they evolve to homogeneous RNA?

Kim put them to the test, pitting potential primordial hybrids against modern RNA and manually copying the chimeras to imitate the process of RNA replication. Pure RNA, he found, is more efficient, more precise, and faster than its heterogeneous counterparts. In another surprising discovery, Kimfound that the chimeric oligonucleotides like ANA and DNA could have helped RNA evolve the ability to copy itself. Intriguingly, he said, some of these variant ribonucleotides have been shown to be compatible with or even beneficial for the copying of RNA templates.

If the more efficient early version of RNA reproduced faster than its hybrid counterparts, it would, over time, out-populate its competitors. Thats what the Szostak team theorizes happened in the primordial soup: Hybrids grew into modern RNA and DNA, which then outpaced their ancestors and, eventually, took over.

No primordial pool of pure building blocks was needed, Szostak said. The intrinsic chemistry of RNA copying would result, over time, in the synthesis of increasingly homogeneous bits of RNA. The reason for this, as Seohyun has so clearly shown, is that when different kinds of nucleotides compete for the copying of a template strand, it is the RNA nucleotides that always win, and it is RNA that gets synthesized, not any of the related kinds of nucleic acids.

So far, the team has tested only a fraction of the possible variant nucleotides available on early Earth. So, like those first bits of messy RNA, their work has just begun.

Read the rest here:
Study likens Earth's evolution to creation of Frankenstein's monster - Harvard Gazette

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