Sonntag, 13. Mai 2007

Neue IQ-Gene entdeckt?

Der New Scientist schreibt:

It seems you owe your brains to your parents. Inherited variations in two genes are linked with reasoning, memory and brain volume. One of the genes is also involved in Alzheimer's disease. (...)

Sudha Seshadri at Boston University and colleagues assessed the cognitive abilities of 705 healthy adults with standard tests and used MRI scans to measure the volume of their brains. The researchers also scanned 100,000 single-nucleotide polymorphisms - small variations in the genome sequence - in participants' DNA for links to mental performance.

The strongest links were in the genes SORL, involved in abstract reasoning and the processing of amyloid protein in Alzheimer's disease, and CDH4, which seems to predict brain volume.

"A number of these genes have a role throughout life, perhaps in determining brain volume or the degree of age-related decline," Seshadri said at an American Academy of Neurology meeting in Boston on 2 May.

Und ein weiteres Lern- und Gedächtnis-Gen, KLK8, das Neuropsin II herstellt, unterscheidet uns offenbar von den Schimpansen und Orang-Utans (New Scientist):

Bing Su and his colleagues at the Kunming Institute of Zoology in China had earlier demonstrated that neuropsin II is made by humans but not by lesser apes and old-world monkeys. Now they have shown that orang-utans and chimpanzees don't make it either.

KLK8 is the first human-specific discovery of a "splice variant" - a gene that is roughly the same in different species but is "cut and pasted" differently when it is expressed, resulting in proteins with new functions. Su's team have shown that KLK8 arose through a single mutation in DNA when a thymine nucleotide was exchanged for an adenine.

This small change had a huge impact, causing 45 additional amino acids to be loaded into the protein that the gene expresses. The changes make humans' neuropsin II significantly different from the neuropsin made by other mammals.

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