Examples of Mutations

Question 1

Sickle cell anaemia

Answer 1

Caused by an autosomal recessive missense mutation in the beta-globin gene

• A to T resulting in a Glu to Val change

Question 2

Phenylketonuria

Answer 2

Caused by a missense mutation in the phenylalanine hydroxylase gene
- C to T results in Arg to Trp change in protein
- Autosomal recessive trait - wild-type is haplosufficient

Question 3

Pelizaeus-Merzbacher-like disease

Answer 3

• Caused by autosomal recessive nonsense mutation in gap junction protein
• C to T change resulting in Arg to Stop codon change

Question 4

Beta-thalassaemia

Answer 4

Frameshift mutation due to deletion of AA

Question 5

Cystic Fibrosis

Answer 5

• Caused by a 3 base deletion in the CFTR gene
• Results in loss of a Phe residue from the protein - autosomal recessive

Question 6

BRCA1 & Breast Cancer

Answer 6

A rare variant in BRCA1 gene results in over 80% lifetime risk / penetrance of breast cancer
- Dominant mutation - wild-type is haploinsufficient