Chapter 3: Handy Genes

The concept of genes, which are stretches of DNA enclosed in every cell of our body, has always grasped my attention. The most interesting thing that caught my attention in this chapter was the fact that you can add a very small amount of chemicals or ingredients to an object's cells and recieve dramatic outcomes resulting in a totally different function. For example, when Mary Gasseling took a little patch of tissue from the pinky side of the chicken's limb bud, and transplanted it to the opposite side, the chicken's wing had a full duplicate set of digits. The pattern of the replica were mirror images of the normal set. The zone of polarizing activity (ZPA) is simply a patch of tissue, however, it is capable of controlling the formation of fingers and toes. In the diagram, you can see that moving a slight patch of tissue, ZPA, causes the fingers to be duplicated receiving a mirror image (50). Another thing that appealed to me was that the DNA recipe to build upper arms, forearms, wrists, and digits is virtually identical in every creature that has limbs. Therefore, humans and various creatures are all similar in one way or another. Also, it was very surprising to learn that the skeletal structures of a sharks' appendages are not similar to Owen's "one bone-two bone-lotsa blobs-digits pattern." Although, they are referred to as bones, they are actually made of cartilage. (sharks are cartilaginous fish, since their skeletons never turn into hard bone).