More guides on this topic

• Revise: Structure of DNA
• Revise: Gene expression
• Revise: Cellular differentiation
• Revise: Genome and mutations
• Revise: Evolution
• Revise: Genomic sequencing
• Video playlist

Related links

• BBC Science
• BBC News: Science
• BBC Nature
• SQA Higher Biology
• The Guardian: Biology
• Nature.com
• Nature Detectives