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प्रश्न
In E.coli, three enzymes β- galactosidase, permease and transacetylase are produced in the presence of lactose. Explain why the enzymes are not synthesized in the absence of lactose.
उत्तर
In the absence of lactose, the repressor protein binds to the operator and prevents the transcription of structural gene by RNA polymerase, hence the enzymes are not produced. However, there will always be a minimal level of lac operon expression even in absence of lactose.
संबंधित प्रश्न
When lactose is present in the culture medium:
Distinguish between structural gene, regulatory gene and operator gene.
A low level of expression of lac operon occurs at all the time. Justify the statement.
______ refers to the phenomenon by which a set of genes are switched on when there is necessity to metabolise a new substrate.
Identify the process described in the following paragraph.
Repressible regulation of gene is seen when the end product of a biosyntbetic pathway like amino acid, is provided in the medium. At this time, internal biosynthesis of amino acid stops. It is negative control so the metabolite (amino acid) turns off a set of genes involved in producing that metabolite.
Which of the following factors regulate gene expression?
Which of the following is not a level at which gene expression can be regulated in eukaryotes?
Genes that are involved in turning on or off the transcription of a set of structural genes are called ______.
Which of the following statements is correct about the role of regulatory proteins in transcription in prokaryotes?
Sometimes cattle or even human beings give birth to their young ones that are having extremely different sets of organs like limbs/position of eye(s) etc. Comment.
The gene which codes for enzyme β-galactosidase ______.
Name the enzyme that catalyses the synthesis of the primary transcript.
List the changes that the primary transcript undergoes to become functional mRNA.
