You are investigating a new bacterial operon that contains five regions (A, B, C, D and E) involved in coordinated regulation of transcription. One is the gene for a regulatory protein, one is the binding site for the regulatory protein, two produce structural enzymes (enzyme 1 and enzyme 2), and one is the promoter for the two enzyme genes. The table below shows data collected for five different bacterial strains. A "+" indicates that the structural enzyme is produced and a "-" indicates that the enzyme is not produced. The "signal" is a molecule that either represses or induces the operon. Use the information to determine how the operon is regulated, and the identity of each region.
Strain Enzyme 1 Enzyme 1 Enzyme 2 Enzyme 2
-signal +signal -signal +signal
A+B+C+D+E+ + - + -
A-B+C+D+E+ - - - -
A+B-C+D+E+ + + + +
A+B+C-D+E+ + - - -
A+B+C+D-E+ + + + +
A+B+C+D+E- - - + -
Part E
Mutations in region B and region D give the same results - when either of these regions is mutated, the operon is expressed under all conditions (called constitutive expression).
You hypothesize that region B is the operator region and that Region D is the repressor protein.
To test your hypothesis, you create two partial diploid lines by introducing a F' plasmid with a wild-type lac operon:
Strain 1: F' A+ B+ C+ D+ E+ / A+ B- C+ D+ E+
Strain 2: F' A+ B+ C+ D+ E+ / A+ B+ C+ D- E+
What experimental results would be predicted by your hypothesis?
Complete this table with the expected results by dragging the "+" and "-" signs to the appropriate location
Genotype
Strain 1 F A+ B+ C+ D+ Et A+ B- C+D+ E
Strain 2 F A+ B+ C+ D+ Et A+ B+ C+ D- E
Enzyme 1 -signal + signal
Enzyme 2 -signal +signal