Question

Two mutations of the Trp operon are identified. In mutant A, the operator sequence has changed and the repressor is not able to bind, while as in mutant B the tryptophan is not able to bind the repressor For the phrase below choose the appropriate answer: These cells are able to synthesize tryptophan Mutant A Mutant B Both Mutant A and Mutant B Neither Mutant A nor Mutant B QUESTION 63 Two mutations of the Trp operon are identified. In mutant A, the operator sequence has changed and the repressor is not able to bind, while as in mutant B the tryptophan is not able to bind the repressor For the phrase below choose the appropriate answer: Tryptophan is able to act as an inducer in these colls Mutant A Mutant B Both Mutant A and Mutant B Neither Mutant A nor Mutant B

Answer 1

Ans- Both mutant A and B

• The tryptophan operon is s example of negative regulation In which the presence of tryptophan turn off the operon.
• The tryptophan molecule binds with the inactive repressor which in turn becomes active repressor.
• This active repressor bind with operator and switch off the operon by blocking RNA polymerase
• The mutant A the repressor is unable to bind with the operator because of sequence alteration. Thus, RNA polymerase will not be blocked and synthesis will occur
• The mutant B tryptophan is not able to bind the repressor hence repressor will remain inactive and RNA polymerase will not be bloacked leading to tryptophan synthesis

Neither A and B

• In mutant A the tryptophan in unable to bind with repressor hence no induction of transcription termination will take place
• In mutant B the active repressor is unable to bind with operator. Therefore no role of tryptophanis seen in transcription of operon