A gene codes for an enzyme in a fungus.
Before a mutation, a section of the gene has the base sequence ATGGAACTTTTCGGC. The first four amino acids coded for are Met–Glu–Leu–Phe.
A mutation removes the fourth base from this section of the gene.
The table shows the amino acids coded for by some triplets of bases.
| Triplet of bases | Amino acid coded for |
|---|---|
| ATG | Methionine (Met) |
| AAC | Asparagine (Asn) |
| TTT | Phenylalanine (Phe) |
| TCG | Serine (Ser) |
Give the sequence of the first four amino acids coded for after the mutation.
Using your answer to part (a), explain why this mutation may cause the enzyme to stop catalysing its reaction.
184 exam-style questions on OCR GCSE Biology 1.2 What happens in cells (and what do cells need)?, covering 1.2.1 Structure of DNA, 1.2.2 Nucleotides and complementary bases, 1.2.3 Protein synthesis, 1.2.4 DNA structure and the proteins made, 1.2.5 Investigating enzymatic reactions, and 1.2.6 Mechanism of enzyme action. Each one has a worked solution and a mark scheme showing where the marks go.