A Kevin Duerinck Genetic Migrations Page
Posted: Friday, May 18, 2001
In some of the strongest evidence yet to support the RNA world—an era in early evolution when life forms depended on RNA—scientists at the Whitehead Institute for Biomedical Research have created an RNA catalyst, or a ribozyme, that possesses some of the key properties needed to sustain life in such a world.
The new ribozyme, generated by David Bartel and his colleagues at the Whitehead, can carry out a remarkably complicated and challenging reaction, especially given that it was not isolated from nature but created from scratch in the laboratory. This ribozyme can use information from a template RNA to make a third, new RNA. It can do so with more than 95 percent accuracy, and most importantly, its ability is not restricted by the length or the exact sequence of letters in the original template. The ribozyme can extend an RNA strand, adding up to 14 nucleotides, or letters, to make up more than a complete turn of an RNA helix.
These results, described in the May 18 issue of Science, suggest that RNA could have had the ability to replicate itself and sustain life in early evolution, before the advent of DNA and proteins. The findings will ultimately help evolutionary biologists address questions about how life began on earth more than three billion years ago.
Until almost two decades ago, many researchers thought that RNA was nothing more than a molecular interpreter that helps translate DNA codes into proteins. Then scientists discovered that not all enzymes were proteins—some were made of RNA. Over the past decade, they have developed techniques for producing new ribozymes in the lab, and a series of studies by the Bartel lab at the Whitehead has been lending credence to the notion of an RNA world. Still, none of the ribozymes generated by the Bartel lab or others in the field possessed the sophisticated properties needed to accurately replicate RNA. The finding reported in Science this week narrows that gap. More
Send page by E-Mail Fewer than 50 people founded the entire population of Europe
Posted: Wednesday, May 9, 2001
Fewer than 50 people founded the entire population of Europe, according to a new and accurate way to read demographic history from the genome.
Scientists previously believed that the 500 million people that live in Europe today are descendants of about 10,000 people who left Africa around 100,000 years ago.
But scientists from the Whitehead Institute at MIT in Cambridge, Massachusetts have found so much genetic evidence of inbreeding, they believe all Europeans probably descended from fewer than about 50 people who interbred together over about 30 generations. This select group may have left Africa about 60,000 years ago.
Their data comes from maps of single nucleotide polymorphisms (SNPs), which are the single letter differences in DNA which can exist between people.
The discovery is good news for medicine because the unexpectedly low degree of genetic variation will make it far easier to isolate the genes that underpin common diseases. "I'm very, very excited about this," said Eric Lander of the Whitehead Institute. [More]
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