LONDON, Aug 4: Scientists have mapped 98 percent of the genome of the mouse in a breakthrough that is expected to speed up the hunt for human genes and improve understanding of how they contribute to diseases.

A consortium of scientists from Britain, Canada and the United States collaborated on the genetic map — regarded as the most important since the human genome was sequenced — which was published on Sunday on Nature online, the website of the science journal Nature.

“It will help identify the common genes between the mouse and humans,” Simon Gregory, leader of the project at the Wellcome Trust Sanger Institute, said in an interview.

Mice and men have a similar number of genes, roughly 30,000, compared to the nematode worm with 18,000 and the fruitfly which has 13,000. But scientists do not know what percentage of genes humans share with the mouse or what all of the genes do.

The genome, or complete list of coded instructions needed to make a mouse, should provide some answers, as well as information that can be used in laboratory research to find the causes and cures for human diseases.

The map provides a framework on which researchers will now assemble the whole-genome shotgun sequence data, the article said.

“The human sequence may be used to facilitate construction of other mammalian genome maps using the same strategy,” and “as an added benefit, the mouse map may now be used as a reference to close gaps in the map of the human genome,” the team said.

When it is complete, the sequence of the mouse genome “will have a huge impact on biological research and human health,” they went on.

MAJOR MILESTONE: Professor Steve Brown, of Britain’s Medical Research Council’s Mammalian Genetics Unit, described the mouse genome as a major milestone in the study of genes in humans and mice.

“Together with the mouse draft sequence, it is transforming the science of mouse genetics and will enormously enhance our ability to understand the role of genes in human disease,” he said.

Scientists liken the genetic mouse map to a geographical atlas. It gives a picture of the landscape with indexes so users can easily focus on and explore a particular region of interest.

Mice are extensively studied in laboratories throughout the world because they breed very quickly and share many genes with humans. Scientists use mouse models to study human diseases and to develop and test new treatments.

The mouse genome is about 10 percent smaller in size than its human equivalent. Gregory said the map will be improved and further developed and should be completed in 2005.

Researchers are already using the mouse genome, which is publicly available, to study diabetes and cancer. It may also lead to advancements in gene therapy — replacing faulty genes with normal versions.

“You can accelerate (the research) from the perspective that you can work on genes in the mouse that hadn’t previously been worked on in humans,” Gregory said.

“Obviously if it is working in a mouse model it gives you better confidence that this particular gene and this particularly method of inserting a gene in DNA successfully may be applied to humans.”

Researchers are also mapping the genome of the cow, pig, rat, cat and other animals.

“One of the key features of this project was using the human genome sequence to accelerate the process of mapping out the mouse genome. The enormous success of this approach points the way for tackling many other mammalian genomes,” Dr David Bentley, the head of Human Genetics at the Wellcome Trust Sanger Institute, said in a statement.

Such a map is an essential guide for navigation allowing the location of any gene or other landmark in the chromosomal DNA, the article in Nature said.

The mouse is a key biological model used by researchers worldwide to determine how diseases occur and evolve in humans as the rodents can develop or be induced to develop a large number of human ailments.

The unravelling of the mouse’s genetic material is an important stage in understanding the specificity of the human genome. The two mammals — mice and men — only recently diverged in the evolution of the species and possess up to 90 percent of identical genes.—Reuters