Chapter 3: Handy Genes

Shubin opens the chapter by discussing the experiments of Randy Dahn, a researcher that manipulated the embryos of sharks and skates by injecting vitamins into the eggs. He explains that studying the structures of simpler creatures often opens a window to new discoveries about our own bodies. I found it interesting that he mentioned that "genetic switches" can control the activity of genes in our cells and how genes turn on and off like a concerto composed of various instruments. Shubin also said that the ZPA, a patch of tissue, allows the "pinky side to be different from the thumb side." He also notes that errors in the Sonic Hedgehog can cause multiple defects in the hand, leading the reader to speculate the importance of these genes. Even the reference to Randy and Tabin's discoveries about the connection between the genes of various animals to ourselves further establishes the connection between human beings and all other living creatures. Even though we all all different in many ways, there is something that connects us all together, starting with the ZPA.