In the genotype presented (genomic plus plasmid genes), which of the following s

Question

In the genotype presented (genomic plus plasmid genes), which of the following statements is consistent with the expression phenotype?

genome: I- P+ O+ Z+ Y-  

plasmid: I+ P+ O- Z- Y+

a. constitutive expression of permease

b. no production of either -gal and permease

c. constitutive expression of -gal and permease

d. -gal and permease can only be made in the presence of lactose

e. no -gal can be produced

2. If a cell has a mutation in the lacY gene that produces a non-functional product, how is regulation of the lac operon affected?

a.The lac operon cannot be induced, because lactose cannot enter the cell.

b.The lac operon cannot be transcribed by RNA polymerase because of the lacY mutation.

c.The lac repressor cannot bind to the operator.

d. Expression of the lac operon is normal because lacY is not required to produce allolactose

Explanation / Answer

e. no -gal can be produced....because plasmid will make repressor and that will bind to operator in genome thus no beta-gal would be formed from genome.wheres in plasmid operator is missing and so is b-gal .,... so plasmid too will also not form b-gal where as plasmid can form permease as permease gene is present there where as genomic DNA wont form permease as it is missing there ...

hence only b-gal could not be formed in both the cases

a.The lac operon cannot be induced, because lactose cannot enter the cell.... lactose enters the cell through permease lac Y product ....

Hope it helps .....Regards

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