Mutations

Question 1

What is a substitution mutation and what does
it cause to happen?

Answer 1

Replacement of a base by a different base in DNA; The effect could be: No effect due to the degenerate nature of the genetic code; introduction of a premature stop codon; a change in the amino acid which may affect the position of bonds that cause the tertiary structure of the protein.

Question 2

What is a deletion and what does it cause to

happen?

Answer 2

A base is removed from the sequence. This causes a frame shift where every triplet code downstream of the mutation is changed. This changes the tertiary structure of the protein

Question 3

Suggest how a mutation can lead to the

production of a protein that has one amino acid

missing.

Answer 3

Loss of 3 bases or triplet code from the exon;

Question 4

Suggest how the production of a protein with

one amino acid missing may lead to a genetic

disorder.

Answer 4

Change in tertiary structure of the protein/active site; So non-functional protein/enzyme;

Question 5

A mutation in the gene coding for an

enzyme could lead to the production of a non-

functional enzyme. Explain how.

Answer 5

Change in base sequence of DNA leading to change in amino acid of enzyme); Change in hydrogen / ionic / disulphide bonds leading to change in the tertiary structure of the active site of enzyme; Substrate not complementary so it cannot bind active site so no enzyme-substrate complexes form;

Question 6

What is an addition mutation and what does

to cause to happen

Answer 6

A base is added into the sequence. This causes a frame shift where every triplet code downstream of the mutation is changed. This changes the tertiary structure of the protein.

Question 7

What is an inversion mutation

Answer 7

A group of bases become separated from the DNA sequence and rejoin at the same position, but back to front. The base sequence is reversed.

Question 8

What is a duplication mutation

Answer 8

One or more bases are repeated, this can cause a frame shift.

Question 9

What is a translocation of bases?

Answer 9

A group of bases becomes separated from the DNA sequence on one chromosome and becomes inserted into the DNA of a different chromosome.

Question 10

Why do mutations occur?

Answer 10

Mutations can occur spontaneously, but the rate can be increased by mutagenic agents such as high energy ionising radiation or mutagenic chemicals.

Question 11

Why do some mutations not change the

primary sequence of a protein?

Answer 11

Due to the degenerate nature of the genetic code, some substitution mutations will code for the same amino acid.