1.Point mutations have been isolated that are simultaneously uninducible for the

Question

1.Point mutations have been isolated that are simultaneously uninducible for the lac, ara, and gal operons,
even in the absence of glucose. Provide two different functions that could be missing in these mutants.

2. The tryptophan operon is under negative control: it is on (transcribing) in the presence of low levels of
tryptophan and off in the presence of excess tryptophan. The symbols a, b, and c represent the gene for
tryptophan synthetase, the operator region, and the repressor- but not necessarily in that order. From the
following data, in which superscripts represent wild-type or defective, determine which letter is the gene,
the repressor, and the operator ( + is tryptophan synthetase activity; - is no activity).

Explanation / Answer

1. The two different functions that could be missing in these mutants could be the: **structure of the repressor might be different so that the inducer cannot bind **structure of the operator might be different which allows the repressor-inducer complex to bind. --------------------- 2. a is repressor     b is tryptophan synthetase     c is operator

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