You are trying to understand how cell shape changes shape in response to treatme
ID: 52055 • Letter: Y
Question
You are trying to understand how cell shape changes shape in response to treatment with a particular chemical. Upon treatment, normal wild type (WT) cells are convert from a flattened irregular shape to a rounded, nearly spherical shape. Previously, another student in the lab identified a mutant that remained flat upon treatment. The gene that encodes the normal protein is called Flat1-and the mutant gene is designated as flat1-. To identify additional genes responsible for this behavior, you mutagenize flat1- cells and look for those that can respond normally to stimulation. You identified cells that contain a “suppressor” mutation in a second gene, called supr1-, that restores the wild-type behavior to cells with flat1- mutation. DNA sequencing reveals the specific amino acid changes in the mutants as shown below:
Shape before treatment
Shape after treatment
Mutations
Flat 1 (WT) & Supr 1 (WT)
Flat
Round
None
flat1- (mutant) & Supr 1 (WT)
Flat
Flat
Arg to Asp change in Flat 1
Flat 1 (WT) & supr1- (mutant)
Flat
Flat
Glu to Lys change in Supr 1
flat1- (mutant) & supr1- (mutant)
Flat
Round
Arg to Asp change in Flat 1 & Glu to Lys change in Supr 1
Deleted Flat 1 (WT) & deleted Supr 1 (WT)
Flat
Round
No Flat 1 or Supr 1 change at all
These data suggest that Flat 1 protein binds to Supr 1 protein and this dimerization is required for the change in cell shape. Provide a plausible mechanism of how Flat 1 and Supr 1 interact to regulate cell shape using the data above to support your claim. Explain your reasoning.
Shape before treatment
Shape after treatment
Mutations
Flat 1 (WT) & Supr 1 (WT)
Flat
Round
None
flat1- (mutant) & Supr 1 (WT)
Flat
Flat
Arg to Asp change in Flat 1
Flat 1 (WT) & supr1- (mutant)
Flat
Flat
Glu to Lys change in Supr 1
flat1- (mutant) & supr1- (mutant)
Flat
Round
Arg to Asp change in Flat 1 & Glu to Lys change in Supr 1
Deleted Flat 1 (WT) & deleted Supr 1 (WT)
Flat
Round
No Flat 1 or Supr 1 change at all
Explanation / Answer
Based on the DNA sequence results it is shown that when ever there is a change in both the Flat 1 and Supr 1 gene (Arg to Asp change in Flat 1 & Glu to Lys change in Supr 1) there is change in phenotype. And also the change in phenotype occurs in the normal form of the gene and suppressor, It shows that the suppressor gene changes the Flat gene in the Arg when it interacts, hence when ever there is mutation in that region along with suppressor gene changes itself and the protein Flat to provide the phenotype. Change in only one gene does not give rise to the phenotype. They interact to change each other and provide the phenotype.
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