Are codons important for cloning animals?
While all organisms use the same code (with a few rare exceptions described above): the precise codon usage can be important in genetic engineering. There is a problem termed ‘codon bias’ that can have a significant effect. When an amino acid can be coded for by multiple codons (e.g. UUA and CUC for leucine) the cell may prefer to use one of these codons and make very few tRNA molecules that recognize the other. If you insert a new gene that uses the host’s unused codon, then translation of the protein is greatly reduced. In such cases researchers may have to deliberately change the sequence of the inserted gene to match the codon bias of the host.
