An E. coli merodiploid has the following genotype: lacI+ lacOc lacZ- lacY+ lacA-/ F’ lacI- lacO+...

An E. coli merodiploid has the following genotype:

lacI⁺ lacO^c lacZ^- lacY⁺ lacA^-/ F’ lacI^- lacO⁺ lacZ⁺ lacY^- lacA⁺

What is this strain’s phenotype in the absence (-) or presence (+) of IPTG?

- IPTG: LacZ⁺ LacY^- LacA⁺ + IPTG: LacZ⁺ LacY⁺ LacA⁺

- IPTG: LacZ^- LacY^- LacA^- + IPTG: LacZ⁺ LacY⁺ LacA⁺

- IPTG: LacZ⁺ LacY^- LacA⁺ + IPTG: LacZ⁺ LacY⁺ LacA⁺

- IPTG: LacZ^- LacY⁺ LacA^- + IPTG: LacZ⁺ LacY⁺ LacA⁺

- IPTG: LacZ^- LacY⁺ LacA^- + IPTG: LacZ^- LacY⁺ LacA^-

Solutions

Expert Solution

lac repressor inhibits the expression of lac operon by binding to the operator of the lac operon, lac repressor is inhibited by inducer so lac operon is expressed if inducer is present.

IPTG is an inducer of the lac operon.

the cell has two operons one in the chromosome and the other in the plasmid.

lacI+ lacOc lacZ- lacY+ lacA- this operon is in the chromosome, from this operon lac repressor encoded by the lac I gene is produced, so the cell will have functional lac repressor, and this operon has constitutive lac operator, lac repressor cannot bind to constitutive lac operator, so this lac operon is expressed always in the cell even if the inducer is absent. from this operon lac Y is expressed other two genes, lac Z and lac A are mutated.

lacI- lacO+ lacZ+ lacY- lacA+ this operon is present on the plasmid this operon is inhibited by the functional repressor produced from the operon in the chromosome, so this operon can be expressed only in the presence of inducer, if IPTG is present this lac operon is expressed.from this operon lac A and lac Z are produced if IPTG is present.

D.- IPTG: LacZ- LacY+ LacA- + IPTG: LacZ+ LacY+ LacA+

gladiator answered 1 year ago

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