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The DNA double helix
Age 15 · Biology
DNA is made of two long strands that twist around each other like a spiral ladder. The strands are held together by rungs, each formed by two matching parts that pair up.
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In the picture
- One strand: a long backbone that forms a side of the ladder
- The other strand: a second backbone running alongside, twisted around the first
- A rung: two paired parts joined in the middle, holding the strands together
- A crossing point: where the strands wind over each other, making the twist
Examples
- A spiral staircase, where the steps stay evenly spaced as the stairs turn
- A twisted rope ladder, whose two side ropes wind around each other while the rungs stay in place
Key takeaways
- DNA has two strands twisted into a double helix.
- The strands are linked by paired rungs along their whole length.
Quiz: The DNA double helix (Age 15)
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How many strands make up the DNA double helix?
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What links the two strands of DNA together?
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Which comparison best describes the shape of DNA?
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