# A dog breeder is investigating coat length in dogs. The allele for long coat (L) is dominant over the allele for short coat (l). A heterozygous long-coated dog is crossed with a homozygous short-coated dog. Describe the possible genotypes and phenotypes of the offspring from this cross, and explain why some offspring may have a short coat despite one parent having a long coat.

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

## Mark scheme (4 marks)

1. Correct identification of the two parental genotypes used in the cross (Ll × ll)
2. Correct offspring genotypes stated as Ll and ll (50% each / 1:1 ratio)
3. Correct offspring phenotypes stated: 50% long coat and 50% short coat
4. Explanation that the short-coat allele (l) is recessive and is only expressed when two copies are present (homozygous recessive genotype ll), which is possible because the heterozygous parent can pass on the l allele

## Key terms

- [heterozygous](https://www.gradenine.co.uk/glossary/heterozygous)
- [homozygous](https://www.gradenine.co.uk/glossary/homozygous)
- [dominant](https://www.gradenine.co.uk/glossary/dominant)
- [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 "Describe and 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-dog-breeder-is-investigating-coat-112b38c0) · Published by Druglandscape Ltd.