A gene in a plant codes for an enzyme.
Scientists study the enzyme in normal plants and in two plants, P and Q. Plants P and Q each have a different mutation.
The Table shows their results.
Table
| Plant | Where the mutation is | Is the enzyme present in the cells? | Activity of the enzyme as a percentage of normal |
|---|---|---|---|
| normal | no mutation | yes | 100 |
| P | coding DNA of the gene | yes | 3 |
| Q | non-coding DNA near the gene | no | 0 |
Explain how the mutation in plant P reduces the activity of the enzyme.
The mutation in plant Q does not change the sequence of amino acids in the enzyme.
Explain why there is no enzyme in the cells of plant Q.
A third plant, R, has a mutation in the coding DNA of the same gene. The activity of its enzyme is 100% of normal.
Suggest why.
186 exam-style questions on OCR GCSE Biology 5.1 Inheritance, covering 5.1.1 The genome, 5.1.2 Environment and phenotype, 5.1.3 Variants and mutations, 5.1.4 How genetic variants influence phenotype, 5.1.5 Asexual and sexual reproduction, 5.1.6 Haploid and diploid, 5.1.7 Meiotic cell division, 5.1.8 Single gene inheritance, 5.1.9 Predicting single gene crosses, 5.1.10 Sex determination, 5.1.11 Multiple gene inheritance, and 5.1.12 Development of our understanding of genetics. Each one has a worked solution and a mark scheme showing where the marks go.