Birds are different from most vertebrates. Aside from the obvious distinctions like wings and feathers, birds have only about half as much DNA per cell as mammals and reptiles. Many biologists had assumed that the diminished bird genome was simply the legacy of some ancient genetic accident, when a huge chunk of DNA was somehow deleted in an ancestral bird. But Austin and Marianne Hughes, a husband-and-wife team of molecular biologists at Penn State, have found evidence that the dearth of DNA in bird cells is no accident. They say it is more likely a crucial adaptation for flight.
The Hugheses compared genetic material from humans and chickens. In both types of bipeds, the Hugheses found, the DNA that actually codes for proteins was about the same length. But in chickens, introns--regions of DNA that don’t seem to code for anything--were on average less than half as long as the ...
