A coding DNA variant changes an mRNA codon from GAA to GAG. Both codons specify glutamic acid. No other codons change.
Which prediction is best supported?
The amino acid sequence stays the same, so the protein may function normally.
The amino acid sequence becomes shorter, so the protein may function normally.
The amino acid sequence gains one base, so the protein must change its shape.
The amino acid sequence gains one amino acid, so the protein must lose activity.
44 exam-style questions on Edexcel GCSE Biology 3.2 DNA and protein synthesis, covering 3.2.1 DNA structure as a polymer, 3.2.2 Genome and gene definitions, 3.2.3 Extracting DNA from fruit, 3.2.4 Base order determines protein shape, 3.2.5 Stages of protein synthesis, 3.2.6 Non-coding DNA variants affecting phenotype, and 3.2.7 Coding DNA variants affecting phenotype. Each one has a worked solution and a mark scheme showing where the marks go.