# A cat has black fur. The allele for black fur (B) is dominant over the allele for white fur (b). The cat is heterozygous for this gene. Explain why this cat has black fur, using the terms genotype, phenotype, dominant and recessive in your answer.

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

## Mark scheme (4 marks)

1. The cat's genotype is Bb (one dominant allele and one recessive allele)
2. The dominant allele (B) for black fur is always expressed when present
3. The recessive allele (b) for white fur is only expressed in the absence of the dominant allele
4. Therefore the phenotype of the cat is black fur because the dominant allele determines the observable characteristic

## 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)
- [recessive](https://www.gradenine.co.uk/glossary/recessive)
- [heterozygous](https://www.gradenine.co.uk/glossary/heterozygous)

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-cat-has-black-fur-the-20bb65f3) · Published by Druglandscape Ltd.