Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Molecular Basis of Inheritance question

2015 · Q60
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /NEET
  3. /Biology
  4. /Molecular Basis of Inheritance
  5. /2015 · Q60

Molecular Basis of Inheritance question

2015 · Q60

NEETBiologyMolecular Basis of InheritanceMCQ+4 / −1
Gene regulation governing lactose operon of E.coli that involves the lac I gene product is
  1. A
    negative and inducible because repressor protein prevents transcription.
  2. B
    positive and inducible because it can be induced by lactose
  3. C
    negative and repressible because repressor protein prevents transcription
  4. D
    feedback inhibition because excess of β\betaβ-galactosidase can switch off transcription
View written solutionFree

Correct answer: A

The control of expression of lac operon is negative (as it is turned off normally) and inducible. Inducible operon is an operon which remains switched off normally but becomes operational in the presence of an inducer (lactose, actually allolactose a metabolite of lactose, in case of lac operon). The inducible operon generally functions in catabolic pathways. In the presence of an inducer, the repressor has a higher affinity for the inducer than for the operator gene.

When lactose is added, a few lactose molecules are carried into the cell by the enzyme lactose permease as small amount of this enzyme is present in the cell even when the operon is not working. These few lactose molecules are converted into allolactose molecules which act as an inducer and bind to the repressor (a product of regulator gene). The repressor-inducer complex fails to join with the operator gene, thus it is turned on.

PreviousNext

More from Molecular Basis of Inheritance

  • In sea urchin DNA, which is double stranded, 17% of the bases were shown to be cytosine, The percentages of the other three bases expected to be present in this DNA are2015 · MCQ
  • Transformation was discovered by :2014 · MCQ
  • Which one of the following is wrongly matched?2014 · Multiple correct
  • Select the correct option ;2014 · MCQ
  • The figure gives an important concept in the genetic implication of DNA . Fill the blanks A, B and C. Includes diagram2013 · MCQ
  • Satellite RNA are present in some :2013 · MCQ
  • Which of the following is not a property of the genetic code ?2013 · MCQ
  • Genes of interest can be selected from a genomic library by using :2013 · MCQ