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The Genetic Code

Biology: Cambridge International A Level, topic 6.2.1

The Genetic Code

The genetic code is the combination of triplet codes (codons) in the genome. There are three important features of the genetic code:

Degenerate

Degenerate

  • The genetic code is degenerate.
  • Some amino acids are encoded by more than one codon (e.g. tyrosine is encoded by TAT and TAC).
  • There are 64 possible triplet codons and only 20 amino acids.
Non-overlapping

Non-overlapping

  • The genetic code is non-overlapping.
  • The non-overlapping nature of DNA means that there is no overlap between triplet codes.
  • Each triplet code is separate from the other triplets in the chromosome.
Universal

Universal

  • The genetic code is universal.
  • The same four bases (A, T, G, C) are used in the DNA of every organism.
  • The same codons encode the same amino acids in every organism.
  • Codons in DNA are transcribed into mRNA and translated into amino acids in every organism.

Test yourself on The Genetic Code

  • Which of the following statements about the genetic code are true?

  • Which of these is NOT a feature of the genetic code?

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