O-Level Molecular Genetics: worked solution

Question

Canavan disease is a genetic condition brought about by a fault in the gene coding for the enzyme aspartoacylase. This enzyme normally breaks down a substance in the brain called N-acetyl-aspartate (NAA). Research indicates that when NAA fails to be broken down, the resulting imbalance of chemicals disrupts the building of the myelin sheath while the nervous system is forming. (a) Explain how a fault in the gene leads to too little of the enzyme being made.

The gene carries the sequence of bases (code) that determines the sequence of amino acids in the aspartoacylase enzyme. A fault (mutation) changes the base sequence, so the correct amino acid sequence cannot be assembled. As a result the enzyme is not made correctly / not made in sufficient amounts, so too little functional enzyme is produced.