Why are there four letters in the genetic alphabet?

Research output: Contribution to journalReview article

40 Citations (Scopus)


We list, without thinking, the four base types that make up DNA as adenine, guanine, cytosine and thymine. But why are there four? This question is now all the more relevant as organic chemists have synthesized new base pairs that can be incorporated into nucleic acids, Here, I argue that there are theoretical, experimental and computational reasons to believe that having four base types is a frozen relic from the RNA world, when RNA was genetic as well as enzymatic material.

Original languageEnglish
Pages (from-to)995-1001
Number of pages7
JournalNature Reviews Genetics
Issue number12
Publication statusPublished - Dec 1 2003


ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Genetics(clinical)

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