GCSE Biology (AQA)
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Inheritance, Variation and Evolution
Reproduction
DNA Base Pairing
0:58
DNA Structure
Spec
4.6.1.5
- A DNA double helix consists of two strands.
- Strand one is on the left and strand two is on the right in the diagram.
- The two strands run in opposite directions.
- Strand two appears upside down or reversed compared to strand one.
- DNA bases on each strand are paired together through hydrogen bonding.
- Specific base pairing: Adenine (A) always pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
- These are referred to as complementary pairings, making the strands complementary to each other.
- It is important to know the base pairings for exams, but the type of bonding (hydrogen bonding) does not need to be described in the exam.
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