DNA has paired building blocks called bases. A pairs with T, and C pairs with G. Read across a rung to find a partner. The two strands run in opposite directions, so an aligned partner is different from a strand written in its usual reading direction.
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How does DNA pairing help preserve information?
Reading level 1 of 5 · EarlyChange
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Base pair
Two complementary DNA bases across the strands.
Complementary
Matching according to the A–T and C–G pairing rules.
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See how it works
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A flattened three-base model with explicit opposite strand directions. Compare aligned pairing with the direction used to read a strand.
What to look for
- Across the three rungs, the aligned partners are T G C.
- Across these rungs, the aligned partners are A A T.
- The highlighted C pairs with G across the rung.
Explain what you noticed
In an aligned diagram, the top bases read C C A from left to right. Which bases sit directly below them?
Keep this idea: A pairs with T and C with G; strand orientation also matters.
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