Northern blot analysis is performed on cellular mRNA isolated from E. coli. The probe used in the northern blot analysis hybridizes to a portion of the lacY sequence. Below is an example of the gel from northern blot analysis for a wild-type lac⁺ bacterial strain. In this gel, lane 1 is from bacteria grown in a medium containing only glucose (minimal medium). Lane 2 is from bacteria in a medium containing only lactose. Following the style of this diagram, draw the gel appearance for northern blots of the bacteria listed below. In each case, lane 1 is for mRNA isolated after growth in a glucose-containing (minimal) medium, and lane 2 is for mRNA isolated after growth in a lactose-only medium.

lac⁻ bacteria with the genotype I⁺ P⁺ O^C Z⁻ Y⁻ 

Verified step by step guidance

1. Understand the context of the problem: Northern blot analysis is used to detect specific RNA sequences in a sample. In this case, the probe hybridizes to the lacY sequence, which encodes the lactose permease protein. The lac operon is regulated by the presence of glucose and lactose in the medium.
2. Analyze the genotype provided: The genotype I⁺ P⁺ Oᶜ Z⁻ Y⁻ indicates that the bacteria have a functional lacI (repressor), a functional promoter (P⁺), a constitutive operator (Oᶜ), and non-functional lacZ and lacY genes. The constitutive operator (Oᶜ) means transcription is always active regardless of the presence of lactose or glucose.
3. Determine the expected mRNA production: Since the lacY gene is non-functional (Y⁻), no lacY mRNA will be produced, even though the operator is constitutive. The probe used in the northern blot specifically hybridizes to lacY mRNA, so no signal will be detected in either lane.
4. Consider the experimental conditions: Lane 1 corresponds to bacteria grown in glucose-containing medium, and lane 2 corresponds to bacteria grown in lactose-only medium. Since lacY mRNA is not produced due to the Y⁻ mutation, the gel will show no bands in either lane.
5. Draw the gel appearance: Based on the analysis, both lane 1 and lane 2 will appear blank (no bands) because the probe does not detect any lacY mRNA in this genotype.

Key Concepts

Northern Blotting

Northern blotting is a technique used to detect specific RNA sequences in a sample. It involves the separation of RNA by gel electrophoresis, transfer to a membrane, and hybridization with a labeled probe that binds to the target RNA. This method allows researchers to analyze gene expression by comparing the levels of mRNA in different conditions or treatments.

Lac Operon

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It consists of structural genes (lacZ, lacY, and lacA) and regulatory elements that control their expression. The operon is typically activated in the presence of lactose and repressed when glucose is available, illustrating the concept of catabolite repression in bacterial gene regulation.

Genotype and Phenotype

Genotype refers to the genetic constitution of an organism, while phenotype is the observable characteristics resulting from the genotype and environmental influences. In the context of the lac operon, the genotype of the bacteria (e.g., lac⁻) determines whether they can produce the proteins necessary for lactose metabolism, which in turn affects their growth in different media.