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⁺ Z⁻ Y⁺

Question

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.
Northern blot showing mRNA bands for lanes 1 and 2 from E. coli grown in glucose and lactose media, respectively.

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

Northern blot showing mRNA bands for lanes 1 and 2 from E. coli grown in glucose and lactose media, respectively.

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

Accepted Answer

Hi, everybody. Let's look at our next question. The results of a northern block analysis for the lack operon can be used to gain insights into the regulation of gene expression. If you identify through gel electrophoresis, that more M R N A is present in samples grown in the presence of lactose compared to samples grown in the absence of lactose. What does this result imply choice? A lactose induces expression of LAC operon genes. Choice B lactose suppresses M R N A transcription of the lac operon choice C A mutation in the LA opera gene had occurred or choice D none of the options is correct. So let's think about the meaning of this result. Remembering that we do have that option that none of our choices are correct. So, in this northern blood analysis, we're looking at how much M R N A is present in these different conditions. And we're looking at presence or absence of lactose and how do we tell how much M R N A is present? You look at the intensity of the bands, the darker, more intense they are, the more M R N A has been expressed. So we're trying to analyze the results of the lac operon. And we noticed that there's more M R N A present in the presence of glucose lactose, excuse me. So the presence of lactose leads to more M R N A. And that would mean higher levels of transcription under those conditions. So the answer we're looking for is choice. A lactose induces expression of LAC operon genes because induction causes higher levels of transcription. So we know we can eliminate choice D since we do have a correct answer, choice, B lacto supresses transcription would not be correct. Since we see more M R N A when lactose is present. And then finally, choice C A mutation in the LAC operon gene. Uh We don't expect to see that since we're just seeing the effect of the presence or absence of lactose, not different strains of the bacteria. So again, if you identify through gel electrophoresis, that more M R N A is present when grown in the presence of lactose, what does this result imply? Choice? A lactose induces expression of lac operon genes. See you on the next video.

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Key Concepts

Northern Blotting

Lac Operon

Gene Expression Regulation