AQA Biology DNA Revision Notes
Master AQA 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 forming a double helix, with sequences of nucleotides that encode the information necessary for the development and functioning of living organisms.
Key Concepts
- 1DNA is made up of nucleotides, each consisting 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).
- 3A pairs with T, and C pairs with G, forming base pairs that hold the two strands of DNA together.
- 4DNA replication is semi-conservative, meaning each new DNA molecule consists of one old strand and one new strand.
- 5Mutations in DNA can lead to changes in protein synthesis, which may affect an organism's traits.
Simple Explanation
DNA is like a recipe book for living things, containing all the instructions needed to build and maintain them. It is made up of smaller units called nucleotides, which come together to form a double helix structure. The order of these nucleotides determines the information that DNA carries, just like the order of words in a recipe determines how a dish is prepared.
Memory Trick
“Remember 'A-T, C-G' to recall the base pairing rules in DNA: Adenine pairs with Thymine, and Cytosine pairs with Guanine.”
Flashcards
What are the four nitrogenous bases in DNA?
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Exam Questions
Describe and explain the structure of DNA. [6 marks]
6 marksView mark scheme hint▾
Mention the double helix, nucleotides, sugar-phosphate backbone, and base pairing.
Explain how DNA replication occurs. [4 marks]
4 marksView mark scheme hint▾
Include the role of enzymes, the semi-conservative nature, and base pairing.
What is meant by a mutation? [2 marks]
2 marksView mark scheme hint▾
Define mutation and give an example, such as a change in base sequence.
Practice Quiz
What is the shape of the DNA molecule?
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