You are studying a particular protein, and find that a mutationchanging an alani

Question

You are studying a particular protein, and find that a mutationchanging an alanine amino
acid residue within the interior of the protein to a valine resultsin a loss of protein
function. You also find that a second mutation (at a differentlocation in the primary
structure) changing a leucine residue to a glycine restores thefunction of the mutant
protein.
a. Using no more than two carefully constructed sentences, tell mewhy the first
mutation results in a loss of protein function?
b. Using no more than two carefully constructed sentences, tell mewhy the second
mutation restores protein function?

Explanation / Answer

Point mutations can be caused by random errors inDNA synthesis. a. The first mutation was a nonsynonymous substitution (ormissense mutation) that resulted in an amino acid changehaving a deleterious effect - the loss of protein function. (alsocalled loss-of-function mutations). b. The second mutation is a missense mutation that just sohappens to translate back into the protein's originalfunction.

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