9. Eukaryotic gene expression Butterflies again! These butterflies have only one
ID: 259917 • Letter: 9
Question
9. Eukaryotic gene expression Butterflies again! These butterflies have only one pigment gene; dark areas have high levels of expression, grey areas have medium levels of expression, and white areas have no pigment expression. You've also isolated a butterfly (Greywing) that has a mutation- the white patches are missing. To determine the regulation of this gene's expression, you construct reporter genes with the promoter (P) and some potential regulatory regions (1-3) from the WT butterfly genome. You insert the six reporter genes into the genomes of WT and Greywing mutants and analyze reporter gene expression. (Note: promoter alone is insufficient to drive reporter gene.)
1. Explain what regulatory element is present (if any) in regions 1-3.
region 1_______________________________________________________________
region 2_______________________________________________________________
region 3_______________________________________________________________
2. Read the description of the experiment carefully. What is the mutation in the GW mutant? Explain whether it is a protein or a cis sequence, which cells are affected (whole body, top wing, white patch, etc) and how the mutation causes the GW pattern.
WT GW mutants 1H2H3H P reporter 1P reporter P reporter P reporter 12-P reporter 2 3 P reporter 2 WT patterrn mutant pattern Reporter gene expression in WT and mutant insectsExplanation / Answer
1. 1, 2 and 3 are cis-regulatory elements (CRE).
A. region 1 is enhancer CRE, which enhances the expression of pigment in whole wing.
B. region 2 is a silencer type CRE which negatively regulate the expression of genes associated with pigment accumulation in the gene.
C. In my point of view, region 3 represent a trans-regulator which positively controls expression of a distant acting gene specifically involved in intense pigment accumulation represented as dark spot at bottom.
2. GW mutant has mutation in the regulatory element 2 (cis element), which control the white patch. Its a cis-element which affect the expression of gene controlling the pigment (melatonin) accumulation into the wing. As show in the figure, in the only presence of regulatory element 2 (a cis element acting as silencer of pigment accumulation) the wings were not able to form pigment; however, in combination with regulatory element 1 and 3, it resulted white patch formation at top
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