Red leaf pigment in a species of plant is made in a reaction controlled by enzyme E. Plants containing more pigment have darker red leaves.
Scientists identified two alleles of the gene for enzyme E. The table shows part of the coding DNA from each allele.
| Allele | Section of coding DNA |
|---|---|
| A | C C T A G G |
| B | C C T T G G |
The scientists produced cloned cuttings from plants with each allele. They grew the cuttings at two temperatures and measured the mean enzyme activity and pigment concentration.
| Allele | Temperature | Mean enzyme activity / µmol product min⁻¹ g⁻¹ | Mean pigment concentration / mg g⁻¹ fresh mass |
|---|---|---|---|
| A | 18 ∘C18\ ^\circ\text{C}18 ∘C | 8.0 | 4.0 |
| A | 34 ∘C34\ ^\circ\text{C}34 ∘C | 7.8 | 3.9 |
| B | 18 ∘C18\ ^\circ\text{C}18 ∘C | 7.5 | 3.7 |
| B | 34 ∘C34\ ^\circ\text{C}34 ∘C | 0.6 | 0.3 |
Explain how the evidence shows that the colour of leaves with allele B depends on an interaction between the genome and the environment.
In your answer, include how allele B could have arisen, how the coding mutation could affect enzyme E and the expected colour of new leaves if a plant with allele B is moved from 34 ∘C34\ ^\circ\text{C}34 ∘C to 18 ∘C18\ ^\circ\text{C}18 ∘C.
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.