Genome of Fruit Fly Finished

The genetic blueprint of the fruit fly - the classic organism for laboratory research - has been completed.

Federally funded scientists at Baylor College of Medicine helped map the two chromosomes that comprise 80 percent of the genome of the fruit fly, Drosophila melanogaster. They collaborated with researchers at the Department of Energy's Lawrence Berkeley National Laboratory in Berkeley, Calif., the University of California at Berkeley and Roswell Park Cancer Institute in Buffalo, N.Y.

Their work, reported in the March 24 issue of the journal Science, completes the genetic map of the fruit fly when combined with data about the rest of the genome provided by other researchers.

For more than a century, the fruit fly has been a major laboratory model for understanding genetics. Because the fruit fly reproduces every two to three days, it is ideal for studying the effects of genetic mutations.

With the entire genetic blueprint now available, researchers can trace virtually any change in the fruit fly's structure and function to specific genes or mutations and draw conclusions about how genetic instructions are transmitted similarly in humans.

The genome is the total collection of genetic information in an organism. In humans, the genome consists of 3 billion base pairs, or chemical units, on 23 pairs of chromosomes. The fruit fly genome, consisting of four chromosomes, is about the size of one human chromosome. Most of the fruit fly's genetic information is on chromosomes 2 and 3, which are mapped in the Science paper.

"Even though the human genome is much more complex, the fruit fly is a lot more like humans than many of us may want to acknowledge," says Dr. Steve Scherer, Baylor assistant professor of molecular and human genetics and senior author of the Science paper. "We share many of the same genes and biochemical pathways."

The approach used to compile the fruit-fly genome has implications for sequencing the human genome, Dr. Scherer says.

The publicly funded researchers divided the genome into moderate-sized sections using bacterial artificial chromosomes (BACs). Then they combined three techniques to create a map showing the location of chemical units on small sections of the genome and how they fit together.

This method differs from the "whole genome shotgun sequencing" approach that the privately funded Celera Genomics Group used to sequence the fruit-fly genome. For the shotgun approach, researchers randomly picked pieces of the genome to sequence and then relied on a computer to assemble them into the "big picture."

Dr. Scherer says the genome map his group constructed served as a "scaffolding" on which the Celera researchers could position their random bits of information.

"As we've seen with the fruit-fly genome, you still need a physical map in order for the shotgun approach to be useful," he says. "And that's likely to become even more evident with the human genome, which is 20 times the size of the fruit-fly genome."

Other researchers at the Baylor Human Genome Sequencing Center who are co-authors of the Science paper are Andrew Arenson, James Durbin, Robert David, Paul Tabor, Michael Bailey, Denise DeShazo and Dr. Richard Gibbs, director of the Center.

The National Human Genome Research Institute of the National Institutes of Health funded the study.

- B. J. ALMOND

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©2006 Texas Medical Center

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