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⁺ Oᶜ Z⁻ Y⁻ 

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 visualizing the presence and size of specific mRNA molecules.

Lac Operon

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It includes genes such as lacZ, lacY, and lacA, which are regulated by the presence of lactose and glucose. Understanding the lac operon is crucial for interpreting the results of the northern blot, as it explains how the bacteria respond to different carbon sources and the expression of the lacY gene.

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 question, the genotype I⁺ P⁺ Oᶜ Z⁻ Y⁻ indicates specific mutations affecting the lac operon, which will influence the expression of mRNA and the resulting bands seen in the northern blot analysis.