Alteration of the sequence of bases in DNA can alter the structure of proteins

Question 1

How might gene mutations(a change to the base sequence) might arise during DNA replication?

Answer 1

• Substitution (swapped) ATG.CCT to ATT.CCT
• Deletion (removed) ATG.CCT to ATC.CT
• Addition ATG.CCT to ATG.ACC.T
• Duplication ATG.CCT to ATG.CCC.CT
• Inversion (reversed) ATG.CCT to ACC.GTT
• Translocation:removed to the same or another chromosome

gene mutations can occur spontaneously

Question 2

How can the mutation rate be increased by mutagenic agents?

Answer 2

Base analogs:can substitute for a base
Altering bases
Altering DNA structure e.g. UV radiation can cause adjacent T’s to pair

Question 3

How can mutations result in a different amino acid sequence in the encoded polypeptide?

Answer 3

Change: GCT.CAG.AGG to GAT.CAG.AGG
No change: GCT.CAG.AGG to GCA.CAG.AGG
-additions,deletions and duplications usually change sequence as it causes a ‘frame shift’ and changes nature of all base triplets downstream from the mutation
-change in amino acid sequence affects tertiary structure of a protein e.g. change the shape of an active site so it’s no longer complementary to its substrate.