mutations

Question 1

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

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

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

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

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

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

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

8. What is a duplication mutation?

Answer 8

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

Question 9

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

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

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.