Which of the following changes represents a missense mutation?

Question

a) AAA (lysine) to AAG (lysine)

b)UUU (phenylalanine) to UAA (stop)

c)AAA (lysine) to AGA (arginine)

d)UGA (stop) to UAG (stop)

e)AUG (methionine) to UGA (stop)

I thinking its a because only one nucleotide was changed vs d has 2 nucleotide substitutions right???

Answer 1

The answer is C.  A missense mutation is a nucleotide change that results in a change of an amino acid.  

In A, the amino acid stays the same so the mutation would have no immediate effect.  

B and E are examples of nonsense mutations which would result in an early stop in the amino acid chain.

Answer 2

c

Answer 3

The first is a synonymous mutation

The second is a nonsense (truncated protein)

The third is missense.

The fourth is synonymous but unlikely to happen in a single go.

The last one is like the second, unless the methionine happense to be the first one and the protein won't be produced at all (knockout).