Short Answer TypeIn the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
One Word AnswersWhat is the regulation of lac operon by repressor referred to?
1. It consists of five genes coding for five enzymes catalysing the synthesis of tryptophan and thus constitute an anabolic pathway.
2. The structure of the operon is more or less similar to that of the lac operon and control of regulator gene R, promoter gene, operator gene O and structural gene. It manifests a functional variation.
3. Here the R gene product (equivalent to the gene of lac operon) produces protein, which by itself unable to operate. This is referred to as apo-repressor.
4. In presence of tryptophan (co-repressor), the functional repressor is formed that now binds to the operator, preventing the transcription of the operon and production of tryptophan.
Tryptophan-Operon.
If the amount of tryptophan increases then it acts as a corepressor. The corepressor joins with the repressor synthesized by regulator gene. The complex of repressor and corepressor binds with operator and switch off the operon as further synthesis of enzyme coded by structural genes stops.
Short Answer Type
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