DNA and RNA differ in one sugar and one base
- The idea
- Predict
- See it
- Why
- Check
The idea
“DNA and RNA use the same parts, so either can have thymine or uracil, ribose or deoxyribose.”
DNA and RNA are both chains of nucleotides, and they share three of their four bases. It's easy to mix up which sugar and base go with which.
The short version
The mistake: DNA and RNA use the same parts, so either can have thymine or uracil, ribose or deoxyribose.
What's actually true: DNA uses deoxyribose and the bases A, T, G and C. RNA uses ribose and A, U, G and C, with uracil in thymine's place.
- A nucleotide has a phosphate, a five-carbon sugar and a base. The sugars differ at the 2' carbon, where ribose has an OH and deoxyribose has only an H.
- Thymine and uracil both pair with adenine. So when RNA is copied from DNA, each A on the template gets a U.
On the exam: DNA gets deoxyribose and T. RNA gets ribose and U. Go by the molecule being built.