Northern blot analysis is performed on cellular mRNA iso...

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.

lac⁻ bacteria with the genotype I⁺ P⁺ O⁺ Z⁻ Y⁺ that has a polar mutation affecting the lacZ gene

Accepted Answer

Hi, everybody. Let's look at our next question. It says northern blot analysis is a laboratory technique used to study gene expression by analyzing the presence and quantity of specific R N A molecules in a sample. In the case of studying the lack operon A northern blood analysis can be used to determine the level of transcription of the lac Z gene under different growth conditions. What is the expected result of the northern blood analysis for the wild pipe stream in a medium containing only lactose choice A? There will be strong visible bands, choice B there will be weak or absent bands, choice C there will be more unclear, overlapping bands or choice D, none of the options is correct. So let's think through what's going on here. Remembering that we have that choice D with the possibility that none of the answers are correct. So whenever we think about northern blot, we want to think about what's in our sample. So our sample will be M R N A molecules and what's our probe? So our sample here is a wild type strain. So wild type strain M R N A. So that would be normal transcription as determined by the lack operon just operating in its usual way. And our probe, it says we are looking for the level of transcription of the LAC Z gene. So that would mean that our probe will be complementary DNA C DNA for the LAC Z M R and E. So we'll say under what circumstances in a wild type strain would we see expression of the lax C gene? Well, our medium, so the conditions we're operating under has only lactose, meaning we have lactose present and no glucose. And when we think about our usual workings of the la opera, we know that this is a case when we have high levels of transcription of our lax Z genes, all our genes operating under that OPERON. But in this case, we're looking for the lax Z gene in particular. And that's because with the presence of lactose, you have the repressor protein is removed from the operator region. And with no glucose, you have the C A MP cap system going on to increase levels of transcription to high levels. So if we see high levels of transcription, what we're going to see is choice a strong visible bands. Our probe, our labeled probe will show a lot of M R N A on our gel. So we know we can eliminate choice D, none of the options is correct. And then again, since we expect to see strong bands, then choice b weaker absent bands and choice c unclear overlapping bands are not correct. So again, the expected result of a northern analysis where we're looking for transcription of the lack Z gene under different conditions for the wild type strain. And a medium containing only lactose is choice. A there will be strong visible bands. See you in the next video.

Key Concepts

Northern Blotting

Lac Operon

Polar Mutation

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