Complete the accompanying table, indicating whether functionally active -galactosidase and permease are produced in the presence and absence of lactose. Use '+' to indicate the presence of a functional enzyme and '−' to indicate its absence. Indicate whether the partial diploid strain is lac⁺ (able to grow on lactose-only medium) or lac⁻ (cannot grow on lactose medium).

Key Concepts

Lac Operon

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It includes genes for β-galactosidase, which breaks down lactose, and permease, which facilitates lactose entry into the cell. The operon is regulated by the presence or absence of lactose, with lactose acting as an inducer that activates the transcription of these genes when present.

Partial Diploidy

Partial diploidy refers to a genetic condition where a bacterium contains two copies of a portion of its genome, typically due to the introduction of a plasmid or a second chromosome segment. In the context of the lac operon, a partial diploid strain can have one copy of the lac operon that is functional (lac⁺) and another that is non-functional (lac⁻), allowing researchers to study gene expression and regulation in a controlled manner.

Inducible Enzymes

Inducible enzymes are proteins whose expression is turned on in response to specific substrates or environmental conditions. In the case of the lac operon, β-galactosidase and permease are considered inducible enzymes because their production is stimulated by the presence of lactose. Understanding this concept is crucial for predicting the behavior of the lac operon under different conditions of lactose availability.