Codon

Definition

A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid or a termination signal during protein synthesis. It is the basic unit of the genetic code.

5 Must Know Facts For Your Next Test

1. There are 64 possible codons, with each one corresponding to a specific amino acid or stop signal.
2. The start codon AUG codes for methionine and signals the beginning of translation.
3. Stop codons (UAA, UAG, UGA) do not code for any amino acids and signal the end of translation.
4. Codons are read in the 5' to 3' direction during translation by the ribosome.
5. Codon usage can be biased in different organisms, influencing gene expression levels.

Review Questions

• What role does the start codon play in protein synthesis?
• How many stop codons exist in the genetic code and what are they?
• Why is it important that codons are read in the correct frame?

Related terms

Anticodon:

A sequence of three nucleotides in tRNA complementary to an mRNA codon.

mRNA:

Messenger RNA that carries genetic information from DNA to the ribosome.

Ribosome:

Cellular machinery that facilitates the translation of mRNA into proteins.