Nucleotide: Sugar, Phosphate, Nitrogenous Base
DNA vs. RNA
DNA |
RNA |
Phosphate | Phosphate |
Sugar: Deoxyribose | Sugar: Ribose |
Nitrogenous Bases: A (Adenine), G (Guanine), C (Cytosine), T (Thymine) | Nitrogenous Bases: A (Adenine), G (Guanine), C (Cytosine), U (Uracil) |
Double-stranded structure (double helix) | Single-stranded structure |
Genetic Material for Most Organisms | Genetic Material for Some Organisms (like Viruses) |
Adenine and Guanine are Purines. Purines are double-ring structures, and thus they are big.
Cytosine, Uracil and Thymine are Pyrimidines. Pyrimidines are single-ring structures, and thus they are small.
Chargaff's Rule: In order to keep the diameter of the double helix consistent, a purine will always pair with a pyrimidine.
Specifically:
DNA → DNA : A pairs with T and C pairs with G.
DNA → RNA : A pairs with U and C pairs with G. T from DNA pairs with A.
RNA → RNA : A pairs with U and C pairs with G.
(Campbell/Reese. Biology: 6th Ed. Copyright 2002 Pearson Ed. Inc.)