Name: Unit 4 Evaluation Question 1: /7 points A naturally occurring dominant mutant in mice is the Doublefoot (Dbf) mutant. Below is an image of the bones from a wildtype (wt) and Doublefoot mutant mouse. a. List a conclusion that you can make from these data. Do you expect that Shh signaling is increased or decreased in these mice? To the right is in situ data of two different genes. One is Ptc1, which is a readout of Shh signaling (more signaling = more Ptc1, less signaling= less Ptc1). The other shows expression of Shh itself. b. What is the name (not just abbreviation) of the region where Shh is expressed in the limb bud? Shh c. List one conclusion you can make about Ptc1 and one conclusion you can make about Shh from these data. In the Shh signaling pathway, is the Dbf mutation upstream or downstream of the Shh protein itself? If you had an animal with both a Shh knockout and the Dbf mutation, would the animal have more or less digits than normal?
Question 2: /5 points To the right is an in situ for an important signaling molecule in the developing limb which is expressed right along the most distal end of the limb bud (in this case an early bud). a. Does this show RNA or protein? b. What is the name (not just abbreviation) of the structure highlighted by this gene s expression? c. Which signal is this? d. What would happen if you removed this structure? e. If you transplanted just this structure to another embryo of an older age, what would happen to that embryo s limb bud? Question 3: /3 points For each of the following, indicate the appropriate axis direction that is correct for the part of limb anatomy (choose one: dorsal, ventral, anterior, posterior, proximal, distal). a. Thumb: Pinkie: b. Palm: Knuckles: c. Stylopod: Autopod:
Question 4: /9 points Draw your own diagram of the mesoderm in an early embryo. You do not have to draw both sides of the body, just one. The neural tube (below) has been done already. Dorsal is up, ventral down. Include the following in your diagram: notochord, lateral plate mesoderm, intermediate mesoderm, paraxial mesoderm. Subdivide paraxial mesoderm into at least two of the three parts discussed in class, indicating where each is, what its name is, and list one type of tissue generated from each. Similarly, subdivide lateral plate mesoderm into its two parts indicating where each is, what each name is, and name a derivative from each. Finally, list a derivative that comes from intermediate mesoderm. Question 5: /4 points Which tissue type is specified by myod? What is the name of the progenitor cells for that tissue type? How must those cells change to differentiate into the mature form of this tissue? Why can you turn myod on once, and it stays on indefinitely?
Question 6: /9 points You discover a novel signaling molecule in newts that is not found in any other species. You want to know if this signaling molecule is: 1) Expressed in blastemas after amputation 2) Necessary for blastema formation 3) Sufficient to form a blastema in uninjured tissue. You generate a standard knockout of this signaling molecule and discover that it s important for gastrulation, so that method won t work. However, anything else discussed in class is fair game. For each of these three questions, outline one experiment that you would perform to address them, and what you would be looking for in each as a readout. Question 7: /3 points One of the most important transcription factors regulating heart development is Nkx2-5, originally called Tinman, because when you knock it out, the organism lacks a heart (just think about it for a minute). You are testing to see if isolation of just cardiac mesoderm into a dish causes a change in the levels of Nkx2-5 by using qpcr. Cardiac mesoderm in the embryo expresses Nkx2-5 at a Ct value of 12. Cardiac mesoderm cultured alone in a dish separate from the embryo now expresses with a Ct value of 15. Did Nkx2-5 expression go up or down? By how much? Is Nkx2-5 expression regulated cell-autonomously or nonautonomously?
Question 8: /5 points What are neoblasts and what species are they from? What type of potency do they have? How do we know that a single neoblast is sufficient to regenerate an entire organism? Is this an example of epimorphosis or morphallaxis? Question 9: /1 points If you take a bead soaked in VEGF and transplant it into an embryo, what do you think will happen? Question 10: /4 points a. The primary site of hematopoiesis changes several times during development. Name one area where hematopoiesis happens in the embryo, but not in the adult. Then, name where hematopoiesis happens in adult mammals. b. Many other changes happen to the circulatory system during development. Name one more thing about the circulatory system that is different in embryos and adults, and describe how it is different in the two.
Predicted Score: /50 Actual Score: /50