Researchers investigate two DNA variants affecting an enzyme. Substrate is in excess in every test. Total reaction rate is proportional to enzyme quantity multiplied by activity per molecule.
The table shows results relative to cells without either variant.
| Variant | Enzyme quantity | Total reaction rate |
|---|---|---|
| P | 50% | 50% |
| Q | 100% | 25% |
Which explanation best fits both results?
P reduces gene expression; Q alters the enzyme's active-site shape.
P alters the enzyme's active-site shape; Q reduces gene expression.
P reduces gene expression; Q increases the enzyme's active-site activity.
P increases gene expression; Q alters the enzyme's active-site shape.
76 exam-style questions on AQA GCSE Biology 6.1 Reproduction, covering 6.1.1 Sexual and asexual reproduction, 6.1.2 Meiosis, 6.1.3 Advantages and disadvantages of sexual and asexual reproduction, 6.1.4 DNA and the genome, 6.1.5 DNA structure, 6.1.6 Genetic inheritance, 6.1.7 Inherited disorders, and 6.1.8 Sex determination. Each one has a worked solution and a mark scheme showing where the marks go.