Your Inner Fish: Handy Jeans

This chapter.
It was quite interesting chapter. It pretty much just spoke about finding one gene consistent in all animals with limbs. DNA lies the same for different species, but there are genetic switched that turn on and off specific genes during development. Some species have a gene that is turned on while others have it off. Nowadays, experimenters have tried to see if they can turn on some of these genetic switches themselves. They worked with chicken eggs and found that they created another wing by taking a little piece of pinky tissue and moving it to the pointer finger. They then began working with flies. They found a gene that separated the head and wings that was very similar to the one found in chickens. They named this gene "sonic hedgehog".

They found that every limbed animal have this "sonic hedgehog" gene active. They tested it with many other animals and found that they all contained this same gene, all turned on.

ps. i can spell genes. the title was, although without reason, intentionally spelled that way.