Week 2 Shubin Assignment (2S2) Read Chapter three in the Inner Fish, answer the following questions and prepare to discuss this material during week 3 class.
. Compare the genetic recipe that builds our hands with the recipe that build’s a fish’s fins. [this question covers the entire chapter – perhaps consider it last!]
2. TRUE or FALSE: All of the cells of our bodies – nerve cells, skin cells, bone cells, etc. – contain exactly the same DNA as each other.
3. What causes a skin cell to be different from, say, a bone cell?
4. At conception, we start out as a single cell (a sperm cell which has merged with an egg cell). Explain how the plan for our entire body unfolds from the DNA in that single fertilized egg cell (called a zygote).
5. What are limb buds and what will they develop into?
6. What happens to development of limbs when the ZPA (zone of polarizing activity) in the limb bud is removed during embryonic development? How does the timing of removal effect development of the limb?
7. What happens when the ZPA is transplanted to the other side of the limb bud?
8 What happens when a tiny piece of foil is placed between the ZPA patch and the rest of the limb? What conclusion can be made from this experiment?
9. What are the hedgehog and Sonic hedgehog genes and what do they do? Where are they active in the embryo?
10. What animals have the Sonic hedgehog gene?
11. TRUE or FALSE: The DNA recipe to build upper arms, forearms, wrists and digits is virtually identical in chickens (birds), frogs (amphibians), and mice (mammals).
12. Is the recipe that builds our hands new, or does it have deep roots in ancient ancestral creatures? Explain.
13. TRUE or FALSE: Sharks are the most ancient surviving fish that have paired fins and a skeleton (cartilage) inside.
14. Does Sonic hedgehog behave the same way in the development of skates’ (close relatives of sharks and rays) and sharks’ fins as it does in the development of our own hands? Explain.
15. Explain: How did scientists create “fingers” on skates using a protein from a mouse? What is significant about the results?
16. Did the ancient transition of fish fins into limbs involve new DNA? Explain.