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Unformatted text preview: MCDB 112 W10 STUDY QUESTION SET #4 (covers lecture set #4) page 1 1. It is useful to figure out the “gene order” when you have encountered a suite of mutants, each defective in a different gene, that show the same phenotype (in this case, mislocalized P granules). You can hypothesize that they work in the same pathway. Assume that you have antibodies against each of the proteins (called MIV in this species) and can localize the proteins in wild type and mutant embryos. Based on the immunolocalization data below, place the MIV genes in an “order.” Embryo MCDB 112 W10 STUDY QUESTION SET #4 (covers lecture set #4) page 2 3. You set up the experiment diagrammed here. Based on your results, you conclude that at the 4-cell stage, the EMS cell requires a signal from its neighbor, the P2 blastomere, in order to give rise to both E and MS lineages. What (general) results must have you obtained when you set up the experiments (B and C), shown to the right, in order to make this conclusion? 4. How could you determine if the signal sent by P2 was membrane bound or soluble, without actually identifying (cloning, purifying) the signal? 5. Now you focus on 2 other cells, called VUa and VUp. Fate mapping and lineage analysis shows that one VU cell typically gives rise to primary vulva and the other to hypodermis, but if their positions are switched in very early development (as soon as they are born), there is no effect on the embryo (that is, they are initially equivalent in terms of their fate potential). The fates of the VU cells are determined via a conditional mechanism. 5A.There are two basic ways that the VUa and VUp cell fates could be specified. Briefly name and describe these two non-autonomous signaling mechanisms, and be sure to distinguish between them. 5B.You culture isolated VUp and VUa blastomeres together and you observe primary vulva, and hypodermal cell types forming in the dish, just like you would in the embryo (using marker gene expression analysis). Further, if the cells sitting next to the VU cells in the embryo are laser- ablated, the VU lineages are not affected (you still observe primary vulva and hypodermal cell fates in these embryos, though there are other problems). Based on these data, what mechanism likely is operating to specify the VU fates (based on your 5A answer)? You identify a gene, called vul-1 , which is necessary for the acquisition of the proper VU fates. Embryos null for vul-1 do not make primary vulval tissues, though hypodermis still forms. Vul-1 encodes a Notch-type receptor protein. You now make a REPORTER CONSTRUCT that is composed of the regulatory region of the vul-1 gene driving expression of the coding region of Green Fluorescent Protein (GFP). When this protein is made in a cell, the cell fluoresces (glows) green. You make transgenic embryos carrying this reporter construct – all cells in the embryo contain the construct. The embryos are otherwise wildtype (they carry their own copy of a normal vul-1 gene). Answer the questions below (next page) based on your above answers a normal vul-1 gene)....
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This note was uploaded on 11/11/2010 for the course MCDB 112 taught by Professor Staff during the Spring '08 term at UCSB.
- Spring '08