An enzyme converts a colourless substance into a purple pigment. A coding DNA variant changes one amino acid in the enzyme. The same quantity of enzyme is produced, but the cells contain less pigment.
Which explanation best accounts for this result?
The gene is transcribed more often, so more enzyme molecules enter the cells.
The enzyme folds differently, so more substrate molecules bind to its active site.
The enzyme folds differently, so fewer substrate molecules bind to its active site.
The gene is transcribed less often, so fewer enzyme molecules enter the cells.
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.