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Getting a grip on the opposable thumb

Medicine@Yale, 2008 - Nov Dec

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The term “junk DNA” is itself headed for the scrapheap, as scientists discover thousands of sequences in these genetic stretches that control gene expression.

A team led by James P. Noonan, Ph.D., assistant professor of genetics, has now found that changes in a mere 13 genetic “letters” in one such sequence may have unleashed the momentous evolutionary changes that enable humans to manipulate tools and walk upright.

As reported in the September 5 issue of Science, the human version of the sequence strongly activates a reporter gene in the developing limbs of embryonic mice, but nearly identical sequences from ape and monkey genomes do not, suggesting that the 13 differences in the human form helped drive the emergence of the human hand and foot.

“The long-term goal is to find many sequences like this and use the mouse to model their effects on the evolution of human development,” says Noonan.