A-Level Biology DNA Revision Notes
Master A-Level Biology DNA using simple revision notes, key facts and practice questions — all generated by AI for your exam.
DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for life. It is composed of two strands that coil around each other to form a double helix, with sequences of nucleotides encoding the information necessary for the development and functioning of living organisms.
Key Concepts
- 1DNA is made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base.
- 2The four nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
- 3Base pairing occurs between A and T, and between C and G, which is essential for DNA replication.
- 4DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
- 5Mutations in DNA can lead to changes in protein synthesis, potentially resulting in genetic disorders.
Simple Explanation
DNA is like a recipe book for living things, containing instructions on how to build and maintain them. It is made of smaller units called nucleotides, which come together to form a double helix structure. The sequence of these nucleotides determines the traits of an organism. When cells divide, DNA replicates itself to ensure that each new cell has the same instructions.
Memory Trick
“Remember 'A-T and C-G' for base pairing: Adenine pairs with Thymine, and Cytosine pairs with Guanine. Think of it as a 'lock and key' system where only the right pairs fit together.”
Flashcards
What are the components of a nucleotide?
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Exam Questions
Describe and explain the structure of DNA and its significance in genetics. [6 marks]
6 marksView mark scheme hint▾
Include details about the double helix, nucleotide composition, base pairing, and its role in heredity.
Explain how DNA replication occurs and its importance for cell division. [4 marks]
4 marksView mark scheme hint▾
Discuss the semi-conservative nature, enzymes involved, and the outcome of replication.
What is meant by a mutation in DNA? [2 marks]
2 marksView mark scheme hint▾
Define mutation and provide examples of its potential effects on protein synthesis.
Practice Quiz
What is the role of DNA in living organisms?
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