f years of evolutionary history, an indication that it performs a biologically important function. But sometime after the human lineage diverged from its last common ancestor with chimpanzees 5 to 7 million years ago, HAR1 began to change rather dramatically.
"We found 18 differences between chimps and humans, which is an incredible amount of change to have happened in a few million years," Pollard said.
The researchers obtained preliminary evidence that HAR1F was active in the brain. Around that time, Pierre Vanderhaeghen, a neuroscientist at the University of Brussels, visited UCSC to give a seminar. Salama convinced him to include the new gene in a set of experiments he was planning, which would screen for active genes in a series of human embryonic brain sections.
"I had a half-hour meeting with him and gave him a DNA probe for HAR1 to take back to Belgium. I didn't hear anything for a few months, and then I got an e-mail from him saying that it gave a really interesting pattern of expression in the brain," Salama said.
HAR1F was first detected at seven and nine gestational weeks in the part of the embryonic brain that gives rise to the cerebral cortex. In subsequent experiments, collaborators in France looked at the corresponding gene in another primate, a macaque, and found a very similar pattern of expression in the developing macaque brain.
Unlike most known genes, HAR1F does not encode instructions for making a protein to carry out its function. Researchers are discovering a growing number of such "noncoding" genes, many of which produce functional RNA molecules. HAR1F appears to be a novel type of RNA gene, Salama said.
In the typical process by which genes are expressed or activated, the gene's DNA sequence is transcribed to produce a messenger RNA molecule, which then guides the synthesis of a specific protein. The encoded protein carries out the gene's function. Some genes, however,Page: 1 2 3 4 Related medicine news :1
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