A triple-auxotrophic strain of E. coli having the genotype phe⁻ m...

Question

A triple-auxotrophic strain of E. coli having the genotype phe⁻ met⁻ ara⁻ is used as a recipient strain in a transduction experiment. The strain is unable to synthesize its own phenylalanine or methionine, and it carries a mutation that leaves it unable to utilize the sugar arabinose for growth. The recipient is crossed to a prototrophic strain with the genotype phe⁺ met⁺ ara⁺. The table below shows the selected marker and gives cotransduction frequencies for the unselected markers.

Selected Selected Colonies Containing the 
Marker Unselected Marker (%) _
phe⁺ met⁺ ara⁺
met⁺ 4 - 7
phe⁺ - 2 51
met⁺, phe⁺. - - 79
ara⁺ 68 5 -

Use the cotransduction data to determine the order of these genes.

Accepted Answer

Hello everyone and welcome to today's video. So, a proto trophic strain of E coli is taken as a donor for an oxo trophic bacteria mutant to be syntheses of branch chain amino acid leo mutant isom Muin and volin necessary for its survival. So when the medium is selected for wild type, I saw the frequency of genotype observed in the unselected trends, duct tens were as follows. So it was 87% wall type all and the wall type. Now what does this indicate regarding the distance between the three genes as answer choice A we have all three genes are closely related as answer choice B we have the wall type iso gene is further apart from the and the wall type which are very close. Now this as answer choice C, we have the three genes are not in the same strand of DNA. And as answer choice D we have the three genes are very far apart. Now remember that the frequency for these and leo is 87%. Now, the frequency of this genotype of serving the unselected transduction, specifically, this frequency that we're seeing here, this percentage of and, and this absence of isil W type suggests that this ISO gene is going to be further apart from these and WA W type, which are very closely linked. This is why we see such a high frequency this 87% in these. So therefore, the correct answer choice here is going to be answer choice B, this is O type gene is further apart from the type and the type which are very close. And this is the reason why we see this 87% frequency only appearing for W and W type and this absence of the IOW type. Now this is the end of the video. I really hope this helped you and I hope to see you on the next one.

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