SIMPLE COMPOUND COULD HAVE KNITTED DNA, RNA TOGETHER

Chemists at Scripps Research have demonstrated that a simple compound diamidophosphate (DAP}, which was present before life arose on Earth, could have chemically knitted together tiny DNA building blocks called deoxynucleosides into strands of primordial DNA, Science Daily reported.

In a study published in the chemistry journal Angewandte Chemie, they said the finding raises the possibility that DNA and its close chemical cousin RNA arose together as products of similar chemical reactions, and that the first self-replicating molecules -- the first life forms on Earth -- were mixes of the two.

"This finding is an important step toward the development of a detailed chemical model of how the first life forms originated on Earth," says study senior author Ramanarayanan Krishnamurthy, PhD, associate professor of chemistry at Scripps Research.

The finding also nudges the field of origin-of-life chemistry away from the hypothesis that has dominated it in recent decades: The "RNA World" hypothesis posits that the first replicators were RNA-based, and that DNA arose only later as a product of RNA life forms.

A strand of RNA can attract other individual RNA building blocks, which stick to it to form a sort of mirror-image strand -- each building block in the new strand binding to its complementary building block on the original, "template" strand.

If the new strand can detach from the template strand, and, by the same process, start templating other new strands, then it has achieved the feat of self-replication that underlies life.

But while RNA strands may be good at templating complementary strands, they are not so good at separating from these strands.

Modern organisms make enzymes that can force twinned strands of RNA -- or DNA -- to go their separate ways, thus enabling replication, but it is unclear how this could have been done in a world where enzymes didn't yet exist.

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