Codon Bias Essay

Most amino acids are encoded by more than one codon. There are 64 total codons, three of which are stop codons, with 61 of the codons coding for 20 different amino acids. These codons, however, are not used equally. Codon Bias is defined as the deviation from equal usage of synonymous codons. Studies by Jan C. Biro found that the number of synonymous codons shows a significant correlation with the frequency of their respective amino acids. Furthermore, the redundancy of these codons may be evolutionary favorable. For example, genes have an increased resistance to mutation given the multiple possible codons for each amino acid – the third nucleotide in the codon can often be interchanged without causing any significant effect on the primary sequence of the protein (wobble bases). …show more content…
coli can hinder the levels of the produced protein – utilization of the engineered expression strains helps tackle this issue. Engineered E. coli strands help overcome codon bias because they can be constructed to contain extra copies of problematic tRNA genes. Codon-PlusTM strains contain the pRIL plasmid which provides extra genes for specific tRNAs for Arg, Ile, and Leu – AGG/AGA, AUA, and CUA, respectively. A second strain of Codon-PlusTM, CodonPlus-RP, provides extra genes for Arg as well as Pro (CCC). To achieve high-level expression of the desired genes, the cDNAs can be subcloned into an expression vector of the plasmids to produce His-10-tagged fusion proteins in engineered E. coli BL21 (DE3) cells. Rosetta strains work in slightly the same way. They are plasmids that contain the pRARE plasmid that provide all the aforementioned tRNAs as well as correct for the codon GGA which is specific to Gly. These engineered expression strains improve the levels of the protein production but can have adverse effects as well. For example, they may decrease protein