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

Question 1

List the types of gene mutations.

Answer 1

Addition, deletion, substitution, inversion, duplication, translocation.

Question 2

When do gene mutations occur?

Answer 2

Gene mutations occur spontaneously during DNA replication.

Question 3

What increases the rate of gene mutations?

Answer 3

The rate of gene mutations is increased by mutagenic agents.

Question 4

What is the effect of a gene mutation on the encoded polypeptide?

Answer 4

It may result in a different amino acid sequence in the encoded polypeptide.

Question 5

How can a mutation not affect the amino acid sequence?

Answer 5

Due to the degenerate nature of the genetic code, some mutations may not change the encoded amino acid.

Question 6

What is the effect of a frame shift mutation?

Answer 6

It changes the nature of all base triplets downstream from the mutation.

Question 7

What causes a frame shift mutation?

Answer 7

Addition or deletion of bases.

Question 8

How does a substitution mutation affect the polypeptide?

Answer 8

It may result in a different amino acid, but due to the degenerate genetic code, it may code for the same amino acid.

Question 9

What is the relationship between gene mutation and amino acid sequence?

Answer 9

Gene mutations may alter the amino acid sequence, depending on whether the mutation affects the triplet code for specific amino acids.

Question 10

Why do some gene mutations have no effect on the polypeptide structure?

Answer 10

Some mutations do not change the amino acid sequence because the genetic code is degenerate.

Question 11

Explain how a single base substitution causes a change in the structure of
this polypeptide. (3)

Answer 11

1. Change in (sequence of) amino acid(s)/primary structure;

Reject amino acids are formed.
Reject amino acids code.

2. Change in hydrogen/ionic/disulfide bonds;
3. Alters tertiary structure;