The following table shows several bacterial strain lac operon genotypes (some are partial diploids).

a) Fill in the blanks in the “lactose absent” and “lactose present” columns in this table. (+) means significant levels of active ß-galactosidase enzyme can be detected. (–) means no significant levels of active ß-galactosidase enzyme. The first line is filled in for reference.

Strain genotype
Lactose absent
Lactose present

1. lacI+ lacP+ lacO+ lacZ+ lacY+
2. lacI+ lacP+ lacOc lacZ+ lacY+
3. lacI+ lacP+ lacOc lacZ– lacY+
4. lacIs lacP+ lacOc lacZ+ lacY+
5. lacI– lacP+ lacO+ lacZ+ lacY+ / lacI+
6. lacIs lacP+ lacO+ lacZ+ lacY+/ lac I+

b) If lactose is absent and glucose is present in the culture medium of strain 4, will significant levels of active ß-galactosidase enzyme be detected? Explain… in brief, just because there is lots of room left, you don’t need to fill it.