Genetic Code

Free Genetic Code revision notes for OCR A Level Biology – covering specification point 2.1.3(f).

The Nature of the Genetic Code

Genes are sections of DNA that code for proteins (and some code for RNA).

The order of bases in a gene determines the sequence of amino acids in a polypeptide. 

These bases are read in groups of three; this is known as the triplet code, and each group of three bases forms a codon.

Gene with codon, triplet code and amino acid - Genetic Code OCR A Level Biology

The key features of the triplet genetic code are that it is degenerate, non-overlapping, and universal.

PropertyDescriptionBiological Importance
Degenerate64 codons but only 20 amino acids. Most amino acids have multiple codons.
Reduces the impact of point mutations.
Non-overlappingBases are read in triplets (codons), each base used once.Each base affects only one amino acid.
UniversalThe same codons specify the same amino acids in almost all organisms.Evidence for a common evolutionary ancestor.

Want to dive deeper?

Powered by  GDPR Cookie Compliance
Privacy Overview

This website uses cookies so that we can provide you with the best user experience possible. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful.