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प्रश्न
Study the schematic representation of the genes involved in the lac operon given below and answer the questions that follow :
| p | i | p | o | z | y | a |
(a) Identify and name the regulatory gene in this operon. Explain its role in 'switching off' the operon.
(b) Why is the lac operon's regulation referred to as negative regulation?
(c) Name the inducer molecule and the products of the genes 'z' and 'y' of the operon. Write the functions of these gene products.
उत्तर
(a) The regulatory gene in this operon is i gene. The operon is switched off in the absence of the inducer, lactose. In the absence of lactose, the repressor gene is constitutively synthesized from the repressor gene. This active repressor protein binds to the operator gene of the operon and prevents the RNA polymerase to initiate the process of transcription.
(b) The regulation of lac operon is controlled by a repressor that is responsible for switching on and off the operon. When repressor binds to the operator, the operon is switched off and transcription is stopped, the reason why it is called negative regulation.
(c) Lactose is called the inducer molecule.
Gene 'z' codes for beta-galactosidase, which is responsible for the hydrolysis of lactose into galactose and glucose.
Gene 'y' codes for permease which increases the permeability of the cell to lactose.
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संबंधित प्रश्न
Short Answer Question:
Explain the role of lactose in ‘Lac Operon’.
Nucleic acids along with (i) and (ii) form the macromolecular fraction of the cell.
Which of the following gene is responsible for the synthesis of repressor in operon?
Identify the INCORRECT statement/s.
- Regulation of lac operon by repressor is referred to as negative regulation.
- The repressor protein produced by regulator gene binds to the operator region.
- The sequence constituting the operator region is present upstream of promoter region
- Each operon bas a specific 'Operator'.
The wild type E. coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as sugar. Which of the following changes takes place?
The sequence of structural genes in lac operon is ______.
Which enzyme will produce in a cell in which there is a nonsense mutation in the lac Y-gene?
A low level of expression of lac operon occurs at all the time. Can you explain the logic behind this phenomena.
In which condition, lac operon is switched off?
In 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?
