A coding DNA variant changes one amino acid in an enzyme. The altered enzyme has the same activity as the original enzyme under the conditions tested.
Which explanation is consistent with these results?
The changed amino acid prevents any mRNA from attaching to the ribosome.
The changed amino acid prevents the active site from binding the substrate.
The changed amino acid prevents any amino acids from joining into a chain.
The changed amino acid leaves the active site able to bind the substrate.
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.