HIGH FIDELITY. “Quantitative analyses of the code using cost functions derived from physico-chemical properties of amino acids or their evolutionary exchangeability have confirmed the exceptional robustness of the standard genetic code: the probability to reach the same level of error minimization as in the standard genetic code by random permutation of codons is below 10(-6).”
http://www.mdpi.com/2075-1729/7/2/22/htm