It was definitely not a science fiction movie. The animal in the laboratory was real. Besides having two forward-looking eyes, it also had eyes on its knees and eyes on its hind legs. It even had eyes on the back of its head! Yet as strange as it looked, this animal was not a monster. It was simply a fruit fly with eyes in some very strange places. These eyes looked like the fly's normal compound eyes, but a mouse gene transplanted into the fly's own DNA had produced them. How could a mouse gene produce extra eyes in a fly?

As you read this chapter, look for clues to explain how a gene that normall controls the growth of eyes in mice could possibly cause a fly to grow eyes in unusual places.

Then, solve the mystery!