Final answer:
A mutation preventing the formation of the terminator hairpin in the trp operon could lead to the continuous synthesis of tryptophan, regardless of its availability, explaining the bacterial mutation phenotype described.
Step-by-step explanation:
The phenotype described where bacteria synthesize tryptophan continuously, regardless of its presence or absence, could be explained by a mutation affecting the regulation of the trp operon. In normal conditions, a functional trp repressor protein can bind to tryptophan when the amino acid is abundant and subsequently bind to the trp operator to block RNA polymerase, thereby preventing the unnecessary synthesis of tryptophan. However, if the terminator hairpin that normally forms when tryptophan is present can't form due to mutations, this could lead to a loss of the operon's regulation and constant production of tryptophan. Therefore, option (A) the terminator hairpin being unable to form fits the description of the phenotype.
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