Chicken genome should shed light on human DNA

By Malcolm Ritter

updated 1:00 p.m. ET Dec. 8, 2004

Here's something to ponder when you bite into your next chicken wing: A new study says about 60 percent of the genes in the critter you're eating have close cousins in your own DNA.

In fact, the recently deciphered chicken genome should prove a valuable tool for learning about the human version, researchers say in their first detailed analysis of it.

The work is presented by an international team of scientists in Thursday's issue of the journal Nature. The chicken's genome is the first from a bird to be "sequenced," which means scientists identified the 1 billion letters of its DNA code. That job was completed and results made available earlier this year.

Scientists sequence animal genomes in part because they provide points of comparison for shedding light on the human genome. Since the chicken and human genomes have been evolving separately for about 310 million years, it's at a "sweet spot" on the evolutionary tree for such comparisons, said Richard K. Wilson of the Washington University School of Medicine in St. Louis.

Wilson, senior author of the Nature paper, said such analyses can help identify chemical switches that turn genes on and off, for example.

Bones and bird flu
In fact, the new analysis revealed that people have genes related to chicken genes for eggshell proteins, which evidently play a role in bone formation.

Wilson said the chicken genome may also help scientists learn about bird flu, the viral disease found in chickens that might someday set off a deadly worldwide outbreak of human flu. And the genome should also help agricultural scientists track down genes for commercially desirable traits, Jeremy Schmutz and Jane Grimwood of the Stanford Human Genome Center wrote in a Nature commentary.

Wilson and colleagues sequenced and analyzed the genome of the red jungle fowl, the progenitor of domesticated chickens. Its DNA contains only about one-third as many letters as human DNA does, but roughly the same number of genes, 20,000 to 23,000.

One surprise was that chickens have more genes related to sensing odors than expected, suggesting a sharper sense of smell than scientists believed, Wilson said. On the other hand, they have fewer genes devoted to sensing tastes than mammals do, especially for bitter sensations, researchers found.

Unanswered questions
Not surprisingly, chickens were found to lack any version of the human genes for milk, saliva and tooth enamel. These genes were, as the scientists put it in a presentation for reporters, as rare as hen's teeth.

Unfortunately, the new analysis shed no light on a mystery that has long bedeviled humanity: Why does the chicken cross the road?

"That question," Wilson observed in an interview, "is still out there to be answered."