# A gardener notices that some pea plants in their garden produce round seeds and others produce wrinkled seeds. Round seeds are caused by a dominant allele (R) and wrinkled seeds are caused by a recessive allele (r). A pea plant that is homozygous dominant is crossed with a pea plant that is homozygous recessive. Explain what is meant by the terms dominant and recessive, and describe the genotype and phenotype of the offspring produced from this cross.

> Edexcel GCSE Biology (1BI0) — 3.4 Inheritance · Explain · 4 marks

## Mark scheme (4 marks)

1. Dominant means an allele that is always expressed (in the phenotype) / expressed when only one copy is present
2. Recessive means an allele that is only expressed in the absence of a dominant allele / when two copies are present
3. All offspring have the genotype Rr (heterozygous)
4. All offspring have round seeds as their phenotype / the dominant phenotype is expressed in all offspring

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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/a-gardener-notices-that-some-pea-168992f7) · Published by Druglandscape Ltd.