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 molecule that carries the genetic instructions for life. It is composed of two strands forming a double helix, with sequences of nucleotides that encode information for building proteins.
Key Concepts
- 1DNA is made up of nucleotides, each consisting of a phosphate group, a sugar (deoxyribose), and a nitrogenous base.
- 2There are four types of nitrogenous bases in DNA: 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 the process by which DNA makes a copy of itself before cell division.
- 5Mutations in DNA can lead to changes in protein synthesis and may result in genetic disorders.
Simple Explanation
DNA is like a blueprint for building living things. It is made up of smaller pieces called nucleotides, which include a sugar, a phosphate, and a base. The order of these bases forms a code that tells cells how to make proteins, which are essential for life. When cells divide, DNA makes copies of itself to pass on the genetic information.
Memory Trick
“Remember 'A-T, C-G' to recall that adenine pairs with thymine and cytosine pairs with guanine in DNA.”
Flashcards
What are the components of a nucleotide?
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Exam Questions
Describe and explain the process of DNA replication. [6 marks]
6 marksView mark scheme hint▾
Include unwinding of the double helix, base pairing, and formation of new strands.
Explain how mutations can affect protein synthesis. [4 marks]
4 marksView mark scheme hint▾
Discuss changes in the DNA sequence and their potential effects on amino acid sequences.
What is meant by complementary base pairing in DNA? [2 marks]
2 marksView mark scheme hint▾
Define complementary base pairing and give examples of base pairs.
Practice Quiz
What are the four nitrogenous bases in DNA?
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