# In cats, coat colour is controlled by a single gene. The allele for black coat (B) is dominant over the allele for ginger coat (b). A female cat with a black coat is crossed with a male cat with a ginger coat. Half of the offspring have black coats and half have ginger coats. Explain what these results tell us about the genotype of the female parent cat, and state the genotypes of all the offspring produced.

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

## Mark scheme (4 marks)

1. The female parent cat must be heterozygous (Bb)
2. Because a homozygous dominant (BB) female crossed with a ginger (bb) male would produce all black offspring, not a 50:50 ratio
3. Black-coated offspring have genotype Bb
4. Ginger-coated offspring have genotype bb

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](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/in-cats-coat-colour-is-controlled-e65b82af) · Published by Druglandscape Ltd.