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BI379_F09_Exam_1_key - BI379 F09 Exam 1 Key 1 As an OB-GYN...

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BI379 F09 Exam 1 Key 1. As an OB-GYN physician, you have seen your share of odd occurrences. Sadly, the child of one of your recent patients was stillborn and showed some odd features; namely, the child showed cyclopia. The distraught mother wanted to know what caused the death and you started researching. A friend of yours who happens to study zebrafish mentioned that there are various zebrafish mutants which are cyclopic and she happens to be studying one of them. She sends you a partial protein sequence from the mutant gene… GLACGPGRGYGKRRHPKKLTPLAYKQFIPNVAEKTLGASG A. You search the database for human homologs that might align with this sequence (BlastP). What is the human ortholog for this zebrafish protein? sonic hedgehog B. There are also two related human paralogs for this protein. What are their specific names? indian hedgehog, desert hedgehog C. After a bit of research, you conclude it is quite possible that defects in this gene caused the death of the fetus. What is the proper name of the disease associated with this gene? Holoprosencephaly-3 (there are at least 9 holoprosencephalies which map to different genes in the genome). D. Do a bit of research on the gene and briefly tell me what it does and how its function relates to the disease. I wanted to hear something about sonic hedgehog’s molecular activity as a signaling molecule (hedgehog pathway, activating patched/smoothened receptor) and it’s more general function as a specification (or differentiation) molecule. It plays many roles throughout development, such as establishing the dorsal/ventral polarity of the neural tube. However, the important aspect of its function that relates to the disease is its function along the midline to divide territories and, hence, its role in establishing left-right patterns. The clearest example is for cyclopia. SHH is expressed along the ventral midline in the developing nervous system. There is a region destined to become eye tissue (a.k.a. eye primoridium), which normally divides into two. This is aided by SHH, which inhibits the eye-specific transcription factor Pax6 at the midline. Without this inhibition, Pax6-expressing cells are not divided into two areas and grow up as a single cyclopic eye.
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2. Using coliBase, find the locus EnvZ in E. coli K12 strain and the surrounding gene region.
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BI379_F09_Exam_1_key - BI379 F09 Exam 1 Key 1 As an OB-GYN...

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