The Chicken’s Genetic Code Is Cracked

In a strut forward for biology and agriculture, scientists on Wednesday unveiled the first detailed analysis of the genetic blueprint of the chicken -- revealing few surprises, but suggesting that the fowl has the same number of genes as a human and, perhaps, a comparable sense of smell.

The toils of the International Chicken Genome Sequencing Consortium, published today in the journal Nature, usher in a “new era of the molecular genetics of the chicken,” consortium member Jerry B. Dodgson of Michigan State University said at a news conference Wednesday.

The genetic sequence, derived with public funds at Washington University in St. Louis and then analyzed by a larger consortium of scientists, will be “the fundamental tool ... or you might say, a bible” for those who seek to breed faster-growing birds, lower-fat breasts and more prolific egg-layers, Dodgson said.

The chicken analyzed was a red jungle jowl, Gallus gallus, from which all domesticated chickens were bred starting thousands of years ago.

Consortium members have only just begun to peck at the genome data, which have been available free on the Web since March.

So far they have found:

* Chickens have about 20,000 to 23,000 genes, equivalent in number to those of human beings, mice and rats.

* But the chicken genes are packed far tighter: Its genome is one-third the size of the human genome. That is because the human genome is stuffed with much more, seemingly useless, “junk” DNA.

* About 60% of the genes in chickens that code for proteins have counterparts in humans.

* The chicken consortium found that the birds have as many odor-receptor genes as humans, suggesting the chicken’s sense of smell may be better than believed, and at least as good as humans’.

Scientists predict that the chicken genome will aid in evolutionary studies because it is the first bird (and the first descendant of the dinosaurs) to have its genome analyzed.

Chickens and humans diverged down separate evolutionary paths about 310 million years ago -- long enough for nonessential parts of the genomes to have changed structure while the key portions remain the same. Comparing chicken and human DNA will help scientists identify the most essential regions for vertebrate development.

The chicken data should also be useful medically. The first tumor virus and the first cancer gene were both discovered in chickens. A chicken’s development is very similar to that of a mammal’s, but because it all takes place in an accessible egg it is far easier to study.

Also, there are many lines of chickens with genetic diseases to be investigated.

“There are dwarf chickens, there are muscular dystrophy chickens

“That’s been revolutionized,” she said. “It’s just fabulous.”