Midterm 1 September 25, 2001
Part 1: 26 points total
Fill-in the blank (2 points each)
For some questions, there may be more than one correct answer. A list of possible answers is listed at the bottom of this page.
1. During ___________________ the blastomeres divide, but the embryo does not grow in size.
2. During gastrulation, three germ layers are established. The inner-most layer is ______________________, and the outer-most layer is _____________________.
3. Phospholipase C splits PIP2 to yield two active compounds. One of them, ______________________, stimulates the release of calcium. The other product of this reaction is ______________________, and it activates protein kinase C.
4. ZP3 is a glycoprotein located on the ________________________.
5. The first well-described differentiation event during mammalian embryogenesis occurs after compaction, when the _______________________ and _______________________ cells are formed.
6. Drosophila caudal is a _______________________ gene, and even-skipped is a ________________________ gene.
7. A ________________________ transformation is a phenotypic change in which a structure is transformed into a different, but homologous structure. An example is the transformation of antennae to legs in flies carrying an Antennapedia gain-of-function mutation.
8. When a cell undergoes nuclear division in the absence of cytokinesis, a ______________________ is formed.
9. _____________________ is a sea urchin protein that mediates sperm-egg recognition.
Possible answers for fill-in -the-blank questions
Inner cell mass
Inositol 1,4,5- triphosphate
Part 2: 74 points total Short answer. Write in complete sentences.
1. (6 points) Describe sequential induction. (You may include diagrams, but your answer must be in complete sentences.)
2. (12 points)
You are studying the migration of the QL neuroblast during C. elegans development. Loss-of-function mutations in the mab-5 Hox gene disrupt QL migration. Design an experiment to test the hypothesis that the mab-5 gene functions cell-autonomously to regulate QL migration. Describe the experiment, two possible outcomes, and how you would interpret each result.
Experimental design (4 points):
Result #1 and interpretation (4 points):
Result #2 and interpretation (4 points):
3. (12 points)
You create Drosophila that carry a gain-of-function mutation in the Spätzle gene. The resultant protein is always active, regardless of Easter activity. Describe the mutant phenotype that you would expect in Spätzle (gf) embryos. Specifically:
a) How would this affect the stability or localization of the Cactus and Dorsal proteins? Explain your reasoning. (8 points)
b) Would you expect the Spätzle (gf) embryos to have excess dorsal, ventral, posterior, or anterior structures? Explain your answer. (4 points)
4. (12 points)
Describe the biochemical function(s) of the Drosophila Bicoid protein. (4 points)
Researchers investigated bicoid function by injecting bicoid mRNA into different regions of the embryo. What were the results for one such experiment? Describe i) what part of the embryo was injected; ii) how this changed the development of the fly; and iii) how the result was interpreted. (8 points)
5. (7 points)
An important aspect of the theory of differential gene expression is genomic equivalence. Did the cloning of Dolly the sheep prove that genomic equivalence is a universal characteristic of mammalian development? Explain. (3 points) How is this relevant to ethical debates regarding cloning of humans? (4 points)
6. (10 points)
Describe the slow block to polyspermy. Describe how it is initiated, the cellular changes involved, and how the changes block polyspermy (6 points). In your answer, name at least 2 of the molecules involved, and describe their roles in this process (4 points).
7. (15 points)
In arthropods, the arrangement of genes within the Hom-C complex is similar to that found in the phylum chordata. The expression pattern of the Antennapedia (Ant) gene in lobster is similar to that of the Drosophila Ant gene, but there are some differences. You wonder whether the differences are due to the DNA cis-regulatory elements that direct expression of the Ant genes in these two organisms. Alternatively, the differences might be due to the Lobster and Drosophila transcription factors that regulate Ant expression. Design a set of experiments to distinguish between these possibilities. For each experiment, provide possible outcomes and interpret what each result would mean. Describe any control experiments that would be important. Assume that it is feasible to generate transgenic lobsters.