A strain of E. Coli with this genotype:
Lac I- Lac O+ Lac Z+ Lac Y- Lac A+
Would be expected to show what behavior Regarding The expression Of functional Beta Galactosidase ?
A. Uninducible
B. Inducible
C. Constitutive
D. Inducible, But would require a lot more inducer To get good expression
E. Mostly inducible but Somewhat constitutive
To determine the behavior of a strain of E. coli with the given genotype regarding the expression of functional Beta Galactosidase, let's break down the genotype and understand the roles of different genes.
In E. coli, the expression of lactose-metabolizing enzymes, including Beta Galactosidase, is regulated by the lac operon, which consists of several genes involved in lactose metabolism.
The given genotype: Lac I- Lac O+ Lac Z+ Lac Y- Lac A+
- Lac I- : This mutation means that the Lac I gene, which encodes the Lac repressor protein, is non-functional or absent. The Lac repressor normally binds to the operator region (Lac O) and prevents transcription of the lac operon in the absence of lactose or an inducer.
- Lac O+ : This indicates that the operator region (Lac O) is wild type, meaning it can bind the repressor when it is functional.
- Lac Z+ : This denotes that the LacZ gene, which encodes Beta Galactosidase, is wild type and can produce functional Beta Galactosidase.
- Lac Y- : This mutation suggests that the LacY gene, which encodes lactose permease (a protein involved in lactose uptake), is non-functional or absent.
- Lac A+ : This indicates that the LacA gene, which encodes transacetylase (a protein involved in lactose metabolism), is wild type.
Based on this genotype, we can conclude the behavior regarding the expression of functional Beta Galactosidase:
C. Constitutive
In this case, the strain of E. coli with the given genotype lacks a functional Lac repressor (Lac I-), which would typically bind to the operator region (Lac O) and prevent the expression of Beta Galactosidase. Since the Lac repressor is non-functional, the operon is not repressed even in the absence of lactose or an inducer. Consequently, Beta Galactosidase would be constitutively expressed, meaning it is continuously produced regardless of the presence or absence of lactose or an inducer.
To arrive at this answer, I analyzed the mutation(s) present in the given genotype and applied my knowledge of the lac operon and its regulation.