Did a Copying Mistake Build Man's Brain?

05-07-2012 • http://www.livescience.com, Jennifer Welsh

When tested out in mice, researchers found this "error" caused the rodents' brain cells to move into place faster and enabled more connections between brain cells.

When any cell divides, it first copies its entire genome. During this process, it can make errors. The cell usually fixes errors in the DNA. But when they aren't fixed, they become permanent changes called mutations, which are sometimes hurtful and sometimes helpful, though usually innocuous.

One type of error is duplication, when the DNA-copying machinery accidentally copies a section of the genome twice. The second copy can be changed in future copies — gaining mutations or losing parts.

The researchers scanned the human genome for these duplications, and found that many of them seem to play a role in the developing brain. [10 Fun Facts About the Brain]

"There are approximately 30 genes that were selectively duplicated in humans," study researcher Franck Polleux, of The Scripps Research Institute in La Jolla, Calif., said in a statement. "These are some of our most recent genomic innovations."

An extra copy of a gene gives evolution something to work with: Like modeling clay, this gene isn't essential like the original copy, so changes can be made to it without damaging the resulting organism.