# Explain why a plant with the genotype Gg has a green phenotype rather than a yellow phenotype, given that G represents the allele for green colour and g represents the allele for yellow colour.

> Eduqas GCSE Biology — 7.2 Inheritance · Explain · 4 marks

> In pea plants, flower colour is controlled by a single gene. The allele for green (G) is dominant and the allele for yellow (g) is recessive.

## Mark scheme (4 marks)

1. The plant is heterozygous, having one dominant allele (G) and one recessive allele (g)
2. The dominant allele (G) is always expressed when present
3. The recessive allele (g) is only expressed in the absence of the dominant allele / when two copies are present
4. Therefore the green phenotype is expressed because at least one dominant allele is present

## Key terms

- [genotype](https://www.gradenine.co.uk/glossary/genotype)
- [phenotype](https://www.gradenine.co.uk/glossary/phenotype)
- [allele](https://www.gradenine.co.uk/glossary/allele)

## Related

- [Revision notes for Eduqas GCSE Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-a-plant-with-the-4f474874) · Published by Druglandscape Ltd.