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 hereditary material in all living organisms, containing the instructions needed for development, functioning, growth, and reproduction. It is composed of two long strands forming a double helix, with each strand made up of nucleotides that include a phosphate group, a sugar, and a nitrogenous base.
Key Concepts
- 1DNA structure: double helix formed by nucleotides.
- 2Nucleotides consist of a phosphate group, a deoxyribose sugar, and a nitrogenous base.
- 3Base pairing rules: adenine pairs with thymine, and cytosine pairs with guanine.
- 4DNA replication is semi-conservative, producing two identical copies.
- 5DNA is organized into chromosomes within the nucleus of eukaryotic cells.
Simple Explanation
DNA is like a blueprint for living things, telling cells how to grow and function. It is made up of smaller units called nucleotides, which are linked together in a twisted ladder shape called a double helix. Each nucleotide has a base that pairs with another base on the opposite strand, ensuring the information is copied accurately. This process is crucial for making new cells and passing traits to offspring.
Memory Trick
“Remember 'A T and C G' to recall that Adenine pairs with Thymine and Cytosine pairs with Guanine.”
Flashcards
What does DNA stand for?
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Exam Questions
Describe and explain the structure of DNA. [6 marks]
6 marksView mark scheme hint▾
Include details on the double helix, nucleotide composition, and base pairing.
Explain how DNA replication occurs. [4 marks]
4 marksView mark scheme hint▾
Discuss the roles of enzymes and the semi-conservative nature of replication.
What is meant by the term 'complementary base pairing'? [2 marks]
2 marksView mark scheme hint▾
Define the concept and provide examples of base pairs.
Practice Quiz
Which base pairs with adenine in DNA?
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