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A-Level Biology OCR A

Code Amino Triplet Codons Acids Genetic Sequence Mutations

This flashcard explains why the genetic code is a triplet code (to accommodate 20 amino acids), the value of being non-overlapping (allowing varied sequences), and the benefit of being degenerate (reducing the impact of mutations).

Triplet code needed for 20 amino acids; non-overlapping allows varied sequences; degenerate reduces mutation effects.

Front Explain why the genetic code is a triplet code, the value of it being non-overlapping and the reason for it being degenerate.
Back Why it is a triplet code:
  • It is a triplet code because a sequence of 3 bases codes for 1 amino acid
  • If it was a doublet code, there would be 16 possible codons which is not enough for the 20 amino acids
  • Since it is a triplet code it has 64 possible codons which allows multiple codons to code for a single amino acid, reducing the effects of mutations on protein structure



Value of the code being non-overlapping:
  • Each subsequent codon is not limited to the last 2 letters of the codon before
  • This means there can be any combination of amino acids



Why the code is degenerate:
  • The genetic code is a degenerate code because for most amino acids there is more than 1 possible codon
  • This means not all mutations will change the amino acid sequence & primary structure

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