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Scientists ask: was it once an RNA world?

For scientists, the question isn't just how life began. The real question might be: How many times did life begin?

In the early years of Earth's existence, there were so many cataclysmic events like meteor impacts that the oceans would repeatedly boil away and nascent life forms would be wiped out. So the fact that life seems to have started 3.5 billion years ago -- relatively soon after the planet was formed -- indicates that life may have started several times before it had enough time to evolve. Meanwhile, the chances of having the right components fall together in the right configuration seem unbelievably small.

David Bartel, assistant professor of biology, explained to visiting teachers that biologists have wrestled with a chicken-and-egg problem. What was around first: protein, the building blocks of living matter, or nucleic acid, the building blocks of genetic material?

RNA, formed on a DNA template, plays a crucial role in protein synthesis and enables genetic material to replicate itself.

Although there's no question that it's now a protein world, was it an RNA world way back when? "It's the molecular biologist's dream -- and the chemist's nightmare -- that we can deduce that RNA played more of a role than it does today," Professor Bartel said.

To answer questions like these, he and his colleagues are engineering a ribosome to carry out slow, simple reactions in the hope that it will provide clues to whether and how RNA nucleotides can join to another piece of RNA to form different sequences and increase its length. A ribosome is a small cell component in very simple organisms where the sequence of amino acids in a polypeptide chain is specified.

"We're having a lot of fun seeing what RNA can do," Professor Bartel said. "We're using the same techniques that exist in nature to find out about this ultimate evolutionary experiment."

A version of this article appeared in MIT Tech Talk on July 15, 1998.

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