3.8.1 - GENE MUTATIONS

Question 1

sickle cell disease (SCD) is a group of inherited disorders. People with SCD have sickle-shaped red blood cells. A single base substitution mutation can cause one type of SCD.

this mutation causes a change in the structure of the beta polypeptide chains in haemoglobin.

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

Do not include details of transcription and translation in your answer

Answer 1

1. change in sequence of amino acids/primary structure;
2. change in hydrogen/ionic/disulfide bonds;
3. alters tertiary structure;

Question 2

what is a substitution mutation? (1)

Answer 2

replacement of a base by a different base (in DNA)

Question 3

suggest how a mutation can lead to the production of a protein that has one amino acid missing (2)

Answer 3

loss of 3 bases

Question 4

suggest how the production of a protein with one amino acid missing may lead to a genetic disorder (2)

Answer 4

1. change in tertiary structure/active site
2. so non-functional protein

Question 5

a mutation in the gene coding for enzyme B could lead to the production of a non-functional enzyme. explain how (3)

Answer 5

1. changes in base sequence leads to changes in amino acid sequence
2. changes in hydrogen and ionic and disulfide bonds leading to changes in tertiary structure of enzyme
3. enzyme substrate complexes cannot form

Question 6

gene mutations occur spontaneously.

during which part of the cell cycle are gene mutations most likely to occur?

suggest an explanantion for your answer (2)

Answer 6

1. interphase
2. DNA replication occurs here