# A dog has 78 chromosomes in each of its body cells. Explain how genetic information is stored and organised within these chromosomes, and explain why the dog's liver cells and muscle cells contain the same genetic information despite having different functions.

> AQA A-Level Biology (7402) — 3.4.1 DNA, Genes and Chromosomes · Explain · 5 marks

## Mark scheme (5 marks)

1. Chromosomes are made of / contain DNA
2. DNA is a long molecule made up of (two) strands / is a double helix
3. A gene is a small section of DNA / a section of DNA that codes for a protein / codes for a sequence of amino acids
4. Every body cell is produced by mitosis (from the original fertilised egg) / all body cells are derived from the same original cell
5. Different genes are switched on / expressed in different cell types, but the DNA sequence itself is the same in both cell types

## Key terms

- [chromosome](https://www.gradenine.co.uk/glossary/chromosome)
- [gene](https://www.gradenine.co.uk/glossary/gene)

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-dog-has-78-chromosomes-in-26140eac) · Published by Druglandscape Ltd.