Gene control

Human and chimpanzee genes differ by a mere 1.2 per cent, which is insufficient to explain the differences between the two species. About 30 years ago, Mary-Claire King and Alan Wilson had proposed it is not genes but their expression that differentiates us from primates. Now, Matthew Rockman of Duke University, USA, and colleagues have found experimental evidence to support the proposition.

DNA sequences called cis-regulatory elements control how genes express themselves into proteins, in which cells and at what rate. These regulatory elements occur on the same DNA molecule as the gene they control. Rockman and colleagues compared the regulatory evolution of prodynorphin -- a gene expressed in multiple brain and endocrine cell types. They sequenced and analysed prodynorphin regulatory DNA from 74 human chromosomes and 32 primate chromosomes.

They found humans had four copies of the cis-regulatory elements while primates had just one. Further, the human copies also carried five mutations (changes) indicating the evolution of this regulatory element. Similar, other cis-regulatory elements were also found in greater numbers in humans than in primates. The findings appear in PLOS Biology (Vol 3, No 12, December, 2005).

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