Final answer:
A mutation that prevents the formation of the anti-terminator loop in the trp operon would cause premature termination of transcription under low tryptophan conditions, leading to a shortage in the synthesis of tryptophan-producing enzymes.
Step-by-step explanation:
If a mutation prevents the formation of the anti-terminator 2+3 loop in the trp operon, it would lead to an inability to transcribe the structural genes of the operon when tryptophan levels are low. Normally, low levels of tryptophan cause the stalling of the ribosome at region 1, allowing the 2+3 loop to form, preventing the terminator loop from forming and allowing transcription to proceed. Without the anti-terminator loop, the default terminator loop between regions 3 and 4 will form even under low tryptophan conditions, prematurely terminating transcription and preventing the synthesis of enzymes that catalyze the production of tryptophan, potentially leading to a tryptophan shortage within the cell.