Nucleic Acid Bases

Biological Environment > Nucleic Acid Bases

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Nucleic acids mostly use four special bases: thymine, adenine, cytosine and guanine. Notice how flat these bases are.
Notice also that hydrogen and oxygen atoms are scattered around the outside of these molecules. These atoms can make hydrogen bonds with other molecules, such as water. On the other hand their large flat faces were mostly slippery, unable to form hydrogen bonds. The result was that these bases tended to stack up, with their flat faces touching, like a stack of plates, when they fell into water. This could be one reason why nucleic acids formed early in the history of the Earth by joining these flat bases together with a sugar-phosphate backbone.