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时差N小时:遗传错误和大脑理论 Genetic Error and the Big Brain Theory

When cells divide to create copies of themselves or to makesperm and eggs, there is always a chance of genetic error.

Gene duplication, when a regular geneis copied twice, is one of those mishaps.

Gene duplication is usually detrimental and can lead to deformation and death if not caught by thecell’s repair machinery.

But in rare instances, it may also be evolutionarily important.

Scientists researching genes important in brain development believe they have found duplicationerrors that reveal how the human brain increased in size during evolutionary history.

Whilestudying SRGAP2, a gene linked to epileptic seizures, scientists found that the gene had not onlyduplicated once, but a number of times throughout human lineage.

Analysis of the SRGAP2 genes determined that duplications occurred 3.4 and 2.4 million years ago,during which time chimp like ancestors were evolving into the first pre humans and human likeancestors.

To test the function of the duplicated genes, scientists inserted human copies into mice.

The micedidn’t grow larger brains, but their brain cells looked more like human cells with thicker, longer andmore numerous spines to connect with other neurons.

The neurons also grew more quickly,suggesting they could migrate farther during development and enable the brain to become larger.

About 30 genes have undergone gene duplication since humans and chimps diverged from acommon ancestor about six million years ago.

Many of these genes control brain development.Researchers suspect that gene duplication is the key to unlocking the mysteries surroundinghuman brain evolution.

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