Editing Codon usage bias (section)

=== Mutation-selection-drift balance model ===
To reconcile the evidence from both [[Mutation pressure|mutational pressures]] and selection, the prevailing hypothesis for codon bias can be explained by the ''mutation-selection-drift balance model''. This hypothesis states that selection favors major codons over minor codons{{Clarification needed|reason=What is a major or minor codon?|date=December 2024}}, but minor codons are able to persist due to mutation pressure and [[genetic drift]]. It also suggests that selection is generally weak, but that selection intensity scales to higher expression and more functional constraints of coding sequences.<ref name = "pmid18983258" />