June 27, 2000

READING THE BOOK OF LIFE

Studying Model Organisms

By THE NEW YORK TIMES

esearchers have studied the genomes of particular organisms in order to improve sequencing and analysis techniques. These genomes are powerful sets of data against which to compare the human genome.

	HAEMOPHILUS INFLUENZAE (Bacterium) Genome Size 1.8 million base pairs Estimated Genes 1,740 Sequence Completed 1995 Haemophilus was the first independent organism whose genome was sequenced and assembled, opening the door to identifying and understanding genes.
	SACCHAROMYCES CEREVISIA (Yeast) Genome Size 12.1 million base pairs Estimated Genes 6,034 Sequence Completed 1996 A gene known to govern the rate of aging in yeast cells has been found to be active in mice, yielding a new insight into why mice and people age and, possibly, ways of enhancing life span.
	CAENORHABDITIS ELEGANS (Roundworm) Genome Size 97 million base pairs Estimated Genes 19,099 estimated genes Sequence Completed 1998 Human genes that, in defective form, cause Alzheimer's disease and colon cancer have counterpart genes in C. elegans.
	ARABIDOPSIS THALIANA (Member of the mustard family) Genome Size 100 million base pairs (to date) Estimated Genes 25,000 estimated genes (to date) Sequence Still in Progress Arabidopsis uses a chemical, glutamate, much as it is used in the human brain. The plant has genes that encode for glutamate receptors. In the human brain, glutamate acts as a chemical messenger, playing a role in acquiring and storing memories, and possibly contributing to certain mental health ailments. Glutamate also acts as a messenger in plants, communicating the presence of light and regulating light-dependent processes.
	DROSOPHILA MELANOGASTER (Fruit fly) Genome Size 185 million base pairs Estimated Genes 13,061 estimated genes Sequence Completed March 2000 Of the 289 genes known to cause human disease in mutated form, 177 have counterparts in the fly.
	MUS MUSCULUS (Laboratory mouse) Genome Size 3000 million base pairs Estimated Genes At least 50,000 genes Almost every human gene has a counterpart in the mouse, with similar DNA sequences and basic functions. If the 23 pairs of human chromosomes were broken into smaller blocks, those pieces could be reassembled to produce a serviceable model of the mouse genome. HUMANS Genome Size 3000 million base pairs Estimated Genes At least 50,000 genes

Sources: Human Genome Project; Department of Energy