A researcher is studying the regulation of the lac operon in E. coli and has created the following strains with different genotypes:

Strain 1: I⁺ P⁺ O⁺ Z⁺ Y⁺
Strain 2: I⁺ P⁻ O⁺ Z⁺ Y⁺
Strain 3: I⁺ P⁺ O⁺ Z⁻ Y⁺
Strain 4: I⁺ P⁺ O⁺ Z⁺ Y⁻

The researcher wants to determine whether -galactosidase is produced in the presence and absence of the inducer for each genotype. The results of the experiment are shown in the table below:

 Strain   Inducer present     Inducer absent 

     1                    +                        - 

     2                   -                         - 

     3                   +                        + 

     4                   -                         -
 Which of the strain(s) is/are lac⁺?

Suppose a microbiologist has created three partial diploid strains of E. coli, each with different genotypes for the lac operon genes. The researcher wants to determine whether the synthesis of lacZ mRNA is constitutive or inducible in each strain and whether the strain is able to utilize lactose as a carbon source.

Strain 1: cap⁻ I⁺ P⁺ O⁺ Z⁺/ cap⁺ I⁺ P⁺ O⁺ Z⁺
Strain 2: cap⁺ I⁺ P⁺ O⁺ Z⁺/ cap⁺ I⁺ P⁻ O⁺ Z⁺
Strain 3: cap⁺ I⁺ P⁺ O⁺ Z⁻/ cap⁺ I⁺ P⁺ O⁺ Z⁺

Which of the above strain is inducible in the presence of lactose?

The results of a northern blot analysis for the lac operon can be used to gain insights into the regulation of gene expression. If you identified through gel electrophoresis that more mRNA is present in samples grown in the presence of lactose compared to samples grown in the absence of lactose, what does this result imply?

In the lac operon, the mutation in which of the following sites prevents cAMP-CRP binding and also prevents high levels of expression of the lac operon?

In a study of E. coli strains, a haploid strain is found to have inducibly transcribed lac operon genes, but is unable to grow on a lactose medium.
Besides mutation of lacZ gene, what could be the other genotype for this phenotype?

If a cell has an F-factor copy of the lac operon that has the I^S mutation and a genomic copy with the O^C mutation, what would happen to this cell if lactose was present?

Identify the correct statement about the regulation of the lac operon in bacteria.