- The Washington Times - Tuesday, December 17, 2002

Seventy-five or so million years ago, men were, well, mice. So say the scientists who recently announced that they had fully unraveled the mouse genome the long sequence of chemical letters (base pairs) that form the basis for mice to be formed.

By untying those strands, the research teams (whose work was published in the journal Nature) discovered men and mice are more similar than previously thought they share about 99 percent of each other's genes, and have approximately the same number of them 30,000.

A couple of distinctions should be made: Living organisms are composed of billions of smaller parts called cells. Within those cells are protein "machines" that the cell needs to function properly to gain nutrition, to grow, to reproduce. Genes are the assembly and operations manuals for those protein machines. Those sentences and paragraphs of those instructions are written in letters of DNA and stored in chromosome "volumes."

However, like the writings of many columnists (including probably this one) most of what is in those chromosomes seems to have no meaning. The important parts, the genes, form only a small fraction of what is actually in the genome.

So, while the genes of men and mice are quite similar, their genomes are actually rather different only about 5 percent of the mouse genome matches man's precisely. The mouse genome is also about 15 percent shorter (2.5 billion base pairs vs. 2.9). Mice nose out men in olfactory sensitivity, thanks to having more nasal genes. They also have more genes for immune system function and for controlling mating behavior, which could go a long way toward explaining all their scurrying about.

Notwithstanding those differences, mice are the closest relatives to man to have their genome mapped. Comparing the two has helped scientists discover about 1,200 new human genes and 9,000 new mouse genes. That is especially important when it comes to uncovering the root cause of many hereditary diseases, most of which are thought to arise from defective protein machines thus, damaged DNA passed on from one generation to another.

By knocking out specific mouse genes and examining what happens to the unfortunate creatures, scientists should be better able to understand some inherited diseases in humans, such as heart disease, some cancers, and possibly even Alzheimer's and Parkinson's.

For the same reason, areas of extremely tight correspondence between human and mice DNA are particularly interesting to scientists because it means that some sort of pressure is on them to stay virtually unchanged for longer even than Dick Clark. Tiny alterations in those areas result would seem to result in a fate worse than becoming a one-hit wonder. Researchers are particularly intrigued by the close similarities between mouse and human DNA on chromosome 21, the genes on which could play important roles in embryonic development, since defects there are believed to be responsible for at least 30 diseases, ranging from cataracts to Down's syndrome.

It will likely be some time before exact genetic roots of those diseases are fully uncovered, much less treatments made against them. Unraveling the mouse genome alone took more than 200 scientists more than three years, and the way to designer cures for inherited diseases is a maze with more than a few (mouse) traps along the way.

Still, there's something truly exciting about man's ability to use an ancient ancestor to discover new ways to aid his fellows. It's astonishing that so many have used the unraveling of the genome to see so much mouse in man. Not that there isn't a place for humility most men will be doing plenty of squeaking when they see their holiday bills. Still, the Nature paper proves that men are much more than mice.

Indeed, by discovering the mysteries of the mouse genome, it can be truly said that man, once a mouse, has truly roared.

Charles Rousseaux is an editorial writer for The Washington Times.

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