9. You are studying a salamander whose sex determination has been studied and de
ID: 193717 • Letter: 9
Question
9. You are studying a salamander whose sex determination has been studied and determined to be the following. As in most vertebrates, males have high expression of sox3 and fg19, while females have high expression of wnt4. ‘Heat' means that the hotter it gets, the more DMRT1 is repressed. You are experimenting on embryos, trying to determine the effects of particular treatments on whether the embryos develop as males or as females. Do you expect primarily male or female development if you Rear the embros at a very high temperature? Inject the embryos with DMRT1 protein? Inject the embryos with SOX9 protein? Inject the embryos with a chemical that blocks the activity of FGF9 protein? Inject the embros with WNT4 protein? Heat WNT4 10. In the lab, you subject salamanders to mutations and identify mutations that have altered sexual development. How do you expect the following mutations to affect sexual development (more males/more females)? A disabling mutation in the WNT4 coding sequence A disabling mutation in the DMRT1 coding sequence A mutation in the FGF9 binding site on the WNT4 gene 11. What level' of regulation are the following (transcriptional/posttranscriptional/translational/posttranslational) A. Transcription B. Translation C. Splicing D. UbiquitinationExplanation / Answer
Protein DMRT1 and SOX9 are the transcription factor while FGF9, and Wnt4. From the given diagram, SOX9 and FGF9 give rise to male sex whereas Wnt4 give rise to the female sex development. DMRT1 play an essential role in male sex determination as it regulates transcription of SOX9, which means suppression of this transcription factor will lead to default female sex development. SOX9 regulates expression of FGF9 which makes a feedforward loop to SOX9 and therefore, upregulating the expression of both the genes which results in male sex development. FGF9 also play an inhibitory role to suppress the expression of Wnt4 (determine female sex) that has a tendency to suppress the expression of SOX9 gene when promoting female sex development.
9)
Heat causes suppression of DMRT1, therefore, I expect female sex development.
DMRT1 promotes expression of SOX9 gene which leads to expression of FGF9 and through FGF9, suppression of Wnt 4, therefore, I expect male sex development.
SOX9 promotes expression of FGF9 gene which leads to suppression of Wnt4 while making a complex with FGF9 it promotes upregulation of both SOX9 andFGF9 gene, therefore, I expect male sex development.
Blocking of FGF9 inactivation will lead to increase in Wnt4 protein that will inhibit the expression of SOX9 gene, therefore, I expect female sex development
Wnt4 suppress the expression of SOX9 gene, therefore, I expect female sex development.
10)
A disabling mutation in the WNT4 coding sequence will lead to loss in function of a Wnt4 protein, that will lead to higher SOX9 gene expression, therefore I expect male sex development.
A disabling mutation in the DMRT1 coding sequence will lead to a loss in function of DMRT1 gene product, therefore, will not promote expression of SOX9 gene which by default will lead to female sex development.
A mutation on the FGF9 binding site on the WNT4 gene will not allow the FGF9 proteins to downregulate expression of WNT4 gene and expression of this gene leads to suppression of SOX9 gene, therefore, I expect a female sex development.
11) As all products are playing there role in the expression of each protein, therefore, all regulation is at the transcription level.
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