Tuesday, January 09, 2007

Some ethnic differences could be down to the same genes behaving differently

Erika Check:

From dark skin to fiery red hair, the world's ethnic groups all have characteristic physical features. But how does our genome code for these differences? New research shows that it isn't just because different groups carry different genes — some of the variation is down to the same genes being expressed differently.

The study is the latest contribution to the popular new field that uses modern genomic tools to unravel the genetic basis of variation between ethnic groups. Such analyses have only become possible recently, thanks to tools such as the International HapMap Project, published last year, which charts the prevalence of single DNA-letter differences (called single-nucleotide polymorphisms, or SNPs) between different ethnic groups.

Such work has spotted many genetic differences between groups — some of the genes that determine skin or eye colour, for example, have been unpicked. But scientists usually study one trait at a time, and only find a genetic explanation after years of painstaking work.

Richard Spielman, Vivian Cheung and their team at the University of Pennsylvania in Philadelphia, took a much faster approach, screening thousands of traits at once and working back to their genetic roots in mere months.

The team chose a set of 4,197 genes expressed by a single cell line. They then measured the degree to which each gene was active in this cell type in each of three ethnic groups: Caucasians, Chinese and Japanese. The Japanese and Chinese groups gave very similar results, they found. When these were lumped together and compared with the third group, the team found that 1,097 genes, or 25% of the total, were expressed very differently between Asians and Caucasians.

Ethnicity tied to gene expression

Same genes expressed differently behind races looking different

Differences in gene expression between Asians and Europeans

The HapMap and copy number variation

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