DNA base pairing and replication
A pairs with T and C pairs with G; each new strand copies one old one.
The common mistake
Pairing A with G, or using U in DNA (U is RNA only).
Instead: DNA: A–T, C–G. RNA swaps T for U: A–U. Replication is semi-conservative — each new double helix keeps one original strand.
Worked example with Guide me
Write the matching DNA strand for ATGCCA.
- Sugar · What pairs with A?Student · T.
- Sugar · Pair every base.Student · TACGGT.
Answer: TACGGT
Try 3 practice questions
1. Complement of GGATC?
Show answer
CCTAG
2. Which base is in RNA but not DNA?
Show answer
Uracil (U)
3. If 30% of bases are A, what % are T?
Show answer
30%
Quick answers
- What is the most common mistake with dna base pairing and replication?
- Pairing A with G, or using U in DNA (U is RNA only).
- How do I get dna base pairing and replication right?
- DNA: A–T, C–G. RNA swaps T for U: A–U. Replication is semi-conservative — each new double helix keeps one original strand.
- Can you show a worked example?
- Write the matching DNA strand for ATGCCA. TACGGT
Related concepts
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