Intracellular Level of Tryptophan	Ribosome Stalls at Trp Codons	Position of Ribosome When Region 3 Is Transcribed	Secondary Structure of 5′ UTR	Termination of Transcription of trp Operon
High	No	Covers region 2	3+4 hairpin	Yes
Low	Yes	Covers region 1	2 + 3 hairpin	No