DNA & RNA: Comparison
Differences between DNA and RNA
- Unlike DNA, RNA nucleotides never contain the nitrogenous base thymine (T) – in place of this they contain the nitrogenous base uracil (U)
- Unlike DNA, RNA nucleotides contain the pentose sugar ribose (instead of deoxyribose)
Comparing DNA and RNA nucleotides diagram
An RNA nucleotide compared with a DNA nucleotide
- Unlike DNA, RNA molecules are only made up of one polynucleotide strand (they are single-stranded)
- Unlike DNA, RNA polynucleotide chains are relatively short compared to DNA
RNA structure
mRNA as an example of the structure of an RNA molecule
Nucleotide Structure Summary Table
Properties | DNA | RNA |
Pentose sugar | Deoxyribose | Ribose |
Bases | Adenine (A) Cytosine (C) Guanine (G) Thymine (T) |
Adenine (A) Cytosine (C) Guanine (G) Uracil (U) |
Number of strands | Double-stranded (double helix) | Single-stranded |
Examiner Tip
You need to know the difference between DNA and RNA molecules (base composition, number of strands, pentose sugar present). You also need to be able to sketch the difference between ribose and deoxyribose.