The tac promoter, an artificial promoter made from portions of the trp and lacUV5 promoters, has been introduced into a plasmid. It is a hybrid of the lac and trp (tryptophan) promoters, containing the - 35 region of one and the - 10 region of the other. This promoter directs transcription initiation more efficiently than either the trp or lac promoters. Why

answer and explanation

The tac promoter is more efficient than the trp and lac UV5 because as opposed to the trp and lac UV5 promoters, the tac promoter has both a consensus - 35 sequence (a nucleotide sequence of DNA, RNA or amino acids used for inter or intra molecular interactions) and a consensus pribnow box sequence (a prokaryotic sequence with core element at - 10 position).