2011_Questions_Week_10_Answers

2011_Questions_Week_10_Answers - Study questions: 1. You...

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Study questions: 1. You isolate a new zebrafish mutant that has cardia bifida. What is cardia bifida? Based on what you know about heart migration, which tissue type do you think is causing the mutant phenotype? -Cardia bifida is a condition in which the two heart progenitor patches fail two fuse, instead forming two small, beating hearts on each side of the body. Most defects underlying cardia bifida are actually in the underlying endoderm rather than in the cardiac progenitors themselves. The mutations in the endoderm impede the ability of the cardiogenic mesoderm to migrate to the midline. 2. You clone the mutation described above, and find that it is a previously uncharacterized member of a large group of closely related proteins, several of which are also expressed in the same tissue type predicted in question #1. In followup experiments, you attempt to replicate the phenotype by injecting wild-type zebrafish with morpholinos specifically against this gene (you perform exhaustive controls to show that the morpholino knockdown is specifically removing all detectable protein). Surprisingly, the embryos all appear relatively normal. A) What does this data suggest to you about the nature of your mutation? -It suggests that the mutation is not a null allele since other experimental methods removing the protein do not cause the same phenotype. Instead, this mutation might be a dominant negative allele that is able to interfere not only with its own function but also with other related family members. B) How could you then test that this was indeed this type of mutation? -Dominant negative mutations inhibit the activity of endogenous proteins. You could inject mRNA encoding the mutated form of the protein into wild-type zebrafish embryos to see if this gave a cardi bifida phenotype. 3.
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2011_Questions_Week_10_Answers - Study questions: 1. You...

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