Mouse's genetic code published

LOS ANGELES DEC. 4. Scientists in six countries have published almost the entire genetic make-up of the mouse, an accomplishment they say could reveal new insights into how humans have evolved.

The working draft, which lays out the laboratory animal's startling similarity to people, should also streamline the fundamental role that mice already play in the study of human diseases.

The draft code of the mouse, 2.5 billion DNA letters long, comes nearly two years after the human genome was sequenced. Side-by-side, comparisons of the two are already yielding new insights into the human genome, which scientists have unravelled but not fully deciphered.

``We still need help interpreting this book of life,'' said Kerstin Lindblad-Toh of the Whitehead Institute/MIT Center for Genome Research. Mr. Lindblad-Toh is the senior programme manager of the Mouse Genome Sequencing Consortium.

Celera Genomics completed its own draft of the mouse genome more than a year ago, but has made it available only to paying subscribers. The international mouse genome project is being freely published on the Internet, and details will appear in Thursday's issue of the journal Nature. Initial comparison of the mouse and human genomes shows the species are closely related at a genetic level, even though the two last shared a common mammal ancestor 75 million years ago, when dinosaurs still roamed the Earth. The mouse genome is about 14 percent smaller than its human counterpart, but each species has about 30,000 genes — far fewer than estimates of just two years ago. A full 99 percent of a mouse's genes have counterparts in humans, including genes that cause mice to have tails. Researchers said more than 90 percent of genes associated with disease are identical in humans and mice, underscoring the value of the latter in laboratory experiments. Scientists chose the mouse for sequencing because of the rodent's 100-year history as a laboratory instrument.

Another 2.5 percent of each genome, previously discounted as junk, is shared between the mouse and humans but does not contain the codes for genes. These sections may somehow be important in regulating the function of genes, scientists said.

``There's a lot more that matters in the human genome than we realised,'' said the MIT biologist, Eric Lander, director of the Whitehead Institute. Comparing the two genomes allows for the quick identification of those and other important regions because they are most likely to have been preserved since the species diverged.

Identification of a gene does not automatically spell out its function, however. Genetic manipulation of those genes in mice, already commonplace, allows scientists to evaluate their purpose. Genomic comparisons are expected to shed more light on evolutionary history and biological diversity.

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