Selection on Codon Bias

In a wide variety of organisms, Synonymous cottons are used with different frequencies, a phenomenon known as colon bias. Population genetic studies have shown that synonymous sites are under weak selection and that codon bias is maintained by a balance between selection, mutation, and genetic drift. It appears that the major Cause for selection oil codon bias is that certain preferred colons are translated more accurately and/or efficiently. However, additional and sometimes may be even contradictory selective forces appear to affect colon usage as well. In this review, we discuss the current understanding of the ways ill which natural selection participates lit the creation and maintenance of codon bias. We also raise Several open questions: (i) IS natural selection weak independently of the level of codon bias? It is possible that selection for preferred Colons is weak only when colon bills approaches equilibrium and may be quite strong oil genes with colon bias levels that :ire much lower and/or above equilibrium. (ii) What determines the identity of the major colons? (iii) How do Shifts ill codon bias occur? (iv) What is the exact nature of selection oil colon bias? We discuss these questions in depth and offer some ideas on flow they can be addressed using a combination of computational and experimental analyses.