Ch 3: Handy Genes

I enjoyed reading this chapter more than the previous two because it talked about genes. I never knew that certain genes turn on and off in certain cells, making the cells look and behave differently. I learned that in our limbs, certain cells that make up the ZPA tissue have the active Sonic hedgehog gene that causes the tissue to release proteins which allow the pinky and the thumb to be different. And the proof that this gene is found in other creatures like chickens and skates and functions in the same way in their limbs as in ours was interesting because it shows that humans have similar genes as these simpler creatures. After reading that the injection of Vitamin A in the embryos caused the fingers to be duplicated, the idea that as the simpler creatures without wrists and fingers lived, maybe something like the vitamin A caused the hedgehog gene to be active in a creature's cells which resulted in that creature to develop digits. Reading about how when the protein formed from the ZPA tissue was blocked from the cells, digits weren't formed properly, I learned how important our genes are. So overall, I learned a lot about how creatures have similar genes that affect the formation of our appendages. (: