OCR Biology DNA Revision Notes
Master OCR Biology DNA using simple revision notes, key facts and practice questions — all generated by AI for your exam.
DNA, or deoxyribonucleic acid, is the hereditary material in all living organisms and many viruses. It carries the genetic instructions used in growth, development, functioning, and reproduction.
Key Concepts
- 1DNA is composed of nucleotides, which include a phosphate group, a sugar, and a nitrogenous base.
- 2The structure of DNA is a double helix formed by two strands of nucleotides running in opposite directions.
- 3There are four types of nitrogenous bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G).
- 4Base pairing occurs between A and T, and between C and G, which is essential for DNA replication.
- 5DNA replication is semi-conservative, meaning each new DNA molecule consists of one original and one new strand.
Simple Explanation
DNA is like a recipe book for living things, containing instructions on how to build and maintain them. It is made up of smaller units called nucleotides, which link together to form two long strands that twist into a shape called a double helix. The order of the building blocks, or bases, in DNA determines the traits of an organism. When cells divide, DNA makes copies of itself to ensure each new cell has the same instructions.
Memory Trick
“Remember 'A T C G' as 'Apples Taste Crispy Good' to recall the four bases of DNA.”
Flashcards
What are the building blocks of 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 structure, nucleotides, base pairing, and sugar-phosphate backbone.
Explain how DNA replication occurs. [4 marks]
4 marksView mark scheme hint▾
Include the role of helicase, DNA polymerase, and the semi-conservative nature of replication.
What is meant by complementary base pairing? [2 marks]
2 marksView mark scheme hint▾
Define complementary bases and state which bases pair together.
Practice Quiz
What is the primary function of DNA?
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