Amino acid mrna codons that encode for the amino acid isoleucine auu, auc, aua leucine cuu, cuc, cua, cug, uua, uug valine guu, guc, gua, gug phenylalanine uuu, uuc methionine (also the start codon) aug cysteine ugu, ugc alanine gcu, gcc, gca, gcg glycine ggu, ggc, gga, ggg proline ccu, ccc, cca, ccg threonine acu, acc, aca, acg serine ucu, ucc, uca, ucg, agu, agc tyrosine uau, uac tryptophan ugg glutamine caa, cag asparagine aau, aac histidine cau, cac glutamic acid gaa, gag aspartic acid gau, gac lysine aaa, aag arginine cgu, cgc, cga, cgg, aga, agg stop codons uaa, uag, uga 8. how might a gene mutation be silent, with no observable effect on a cell or an organism? a. codons are complementary to anticodons in trna. a gene mutation that changes a codon to its anticodon would have no observable effect on the cell or the organism. b. several codons are stop codons. a gene mutation that inserts a stop codon when only a few amino acids remain in the peptide sequence would have no observable effect on the cell or the organism. c. many proteins are superfluous to the function of a cell. a gene mutation in a gene that encodes an unnecessary protein would have no observable effect on the cell or the organism. d. many amino acids are encoded by multiple codons. a gene mutation that encodes the same amino acid would have no observable effect on the cell or the organism.