Principles of Biochemistry

7.2.2 Differences between RNA and DNA

For major differences exist between RNA molecules and DNA molecules.

1. The sugar unit in the backbone of RNA is ribose; it is deoxyribose in DNA.

2. The base thymine found in DNA is replaced by uracil in RNA. Uracil, instead of thymine, pairs with (forms hydrogen bonds with)adenine in RNA.

3. RNA is a single-stranded molecule; DNA is double-stranded (double helix). Thus RNA, unlike DNA, does not contain equal amounts of specific bases.

4. RNA molecules are much smaller than DNA molecules, ranging from 75 nucleotides to a few thousand nucleotides.