Mutation and protein function

Question 1

Mutation

Answer 1

• Mutation is a change in the genetic material of a cell (or virus)
• Point mutations are chemical changes in just one base pair of a gene
• A single nucleotide change in a DNA template strand can lead to the production of an abnormal protein or another functional variant of the protein

Question 2

Point mutations

Answer 2

Two types:
1. Base-pair substitutions - replacement of a nucleotide and its complement with a different nucleotide pair  no frameshift
2. Base-pair insertions or deletion - addition or loss of nucleotide pairs in a gene sequence  frameshift

Question 3

Silent substitutions don’t result in a change of amino acid

Answer 3

s (indels) more often have a disastrous effect on
protein function than substitutions – because they tend to alter the reading frame (frameshift)

Question 4

Silent mutations

Answer 4

have no effect on the amino acid produced by a codon
because of redundancy in the genetic code

Question 5

Nonsense mutations

Answer 5

change an amino acid into a stop codon, leading to a nonfunctional protein

Question 6

Missense mutations

Answer 6

result in a different amino acid being produced.
Their impact depends on how the amino acid substitution affects the tertiary and quaternary protein structure, and the active site

Question 7

Spontaneous mutations

Answer 7

can occur during DNA replication, recombination or
repair

Question 8

Mutagens

Answer 8

physical or chemical agents that can cause mutations