Question

"Tryptophan self-controls its synthesis." Justify this statement.
A. If a lesser amount of Tryptophan is present in a cell, Tryptophan acts as an inducer and binds to a repressor, leading to the synthesis of enzymes required for its production and thus its synthesis.
B.If an excess amount of Tryptophan is present in a cell, Tryptophan acts as a promoter, preventing the further synthesis of necessary enzymes for its production and thus its synthesis.
C.If an excess amount of Tryptophan is present in a cell, Tryptophan acts as a co-repressor, preventing the further synthesis of necessary enzymes for its production and thus its synthesis.

Answer 1

Repressible system - tryptophan (the effector molecule) interacts with the repressor protein such that it can bind to the operator. 


Answer = C,

Answer 2

Answer:

Option C, If an excess amount of Tryptophan is present in a cell, Tryptophan acts as a co-repressor, preventing the further synthesis of nessary enzymes for its production and thus its synthesis.

Explanation:

When level of tryptophan is high it attache to the trp repressor  and this duo together act as a repressor. Binding of tryptophan changes the shape of the repressor and thus convert it into the active DNA binding form. This duo of tryptophan and trp repressor attaches with the operator and block binding of RNA polymerase to the promoter. In this way further transcription of the operon is prevented.

Hence, option C is correct