# A pea plant has the genotype Tt, where T (tall) is dominant over t (dwarf). Describe what happens when this plant is crossed with a homozygous recessive plant, including the genotypes and phenotypes of all possible offspring.

> Pearson Edexcel International GCSE Biology (4BI1) — 3.2 Inheritance · Describe · 4 marks

> In pea plants, stem height is controlled by a single gene. The allele for tall (T) is dominant over the allele for dwarf (t).

## Mark scheme (4 marks)

1. The homozygous recessive parent has the genotype tt
2. Offspring genotypes are Tt and tt (in equal proportions / 50% each)
3. Tt offspring show the tall phenotype (dominant allele expressed)
4. tt offspring show the dwarf phenotype (only recessive alleles present)

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-pea-plant-has-the-genotype-24b1be44) · Published by Druglandscape Ltd.