If the ugg codons in region 1 of trpl were changed to agg codons, what effect would this have on expression of the trp operon? if the ugg codons in region 1 of trpl were changed to agg codons, what effect would this have on expression of the trp operon? the operon would never be expressed. the operon would be constitutively expressed. the operon would be regulated by tryptophan, but attentuation would be triggered at higher levels of tryptophan than in wild type. the operon would be regulated by tryptophan, but attentuation would be triggered at lower levels of tryptophan than in wild type. the operon would be regulated by arginine levels; high levels of arginine would attenuate expression of trp genes.