The colorful patterns on a butterfly's wings can be mysterious and beautiful. Add a jellyfish gene to a butterfly's genetic makeup, and the result might be even more awe-inspiring.

The jellyfish gene directs production of a chemical compound that glows green when exposed to blue or ultraviolet light. In an African butterfly, addition of this gene makes the butterfly's eyes glow green.

All cells contain long, complicated molecules called DNA. This material provides the instructions that determine what a cell is like and control what a cell does. A gene is a piece of a DNA molecule that has a particular function, which can be passed on from parents to offspring.

In their butterfly experiment, researchers from the State University of New York at Buffalo and Western Kentucky University started with a gene—a snippet of DNA—that allows jellyfish to produce a chemical compound that glows green. They put this DNA snippet into each of more than 10,000 butterfly eggs. About 5 percent of the eggs survived.

Of the eggs that survived and developed to adulthood, about 15 percent had offspring with glowing green eyes when researchers looked at them under ultraviolet light. Our eyes can't see the green glow on their own.

This was the first time that researchers had successfully changed a butterfly's genetic makeup. Others had previously added jellyfish genes to create glowing green eyes in houseflies and some other insects.

Now that they know it's possible, scientists want to try to change butterflies in other ways. One goal is to understand how genes control the development of spots on the insects' wings.

There may be as much information and biology as beauty and mystery in those dramatic streaks of color flitting by on a sunny spring day.—E. Sohn