Wild type E. coli metabolizes the sugar lactose by expressing the enzyme ß-galactosidase. You have isolated a mutant that you call lac1–, which cannot synthesize ß-galactosidase and cannot grow on lactose (Lac–). During an condition Lac– strain, called lac3–, is linked to the Tn5 insertion. From a strain carrying the Tn5 insertion and lac3– mutation you isolate an F’ that caries a region of the chromosome that includes both Tn5 and the linked Lac region. Introduce this F’ into an F– strain carrying lac1– by selecting for Kanr. These merodiploids express ß-galactosidase normally. What does this result tell you about the relationship between the lac3– and lac1- mutations?  

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#Question id: 15278

#Unit 13. Methods in Biology

A DNA sample having mass 1 ng undergoes PCR, the eluted DNA is weighted about 1 microgram, the minimum number of cycles required

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#Question id: 15376

#Unit 13. Methods in Biology

If a protein made up of three subunit α₂βγ (Mr. of α = 25000, β = 50000, γ = 75000) which of the following correctly representing SDS and Native (buffer) gel

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#Question id: 15615

#Unit 13. Methods in Biology

The three stop codons are (I) 5’UAG3’, (II) 5’UAA3’, and (III) 5’UGA3’. when mutagens that specifically induce G•C to A•T mutations on 5’, then what will be the result?

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#Question id: 15616

#Unit 13. Methods in Biology

The diagram below shows the F factor and a portion of the E. coli chromosome that has three different insertion sequences (IS) of the same type as is carried on F.

                     

Describe the three different Hfrs (Hfr #1, Hfr #2 and Hfr #3) that can be formed by recombination between the IS on F and each of the IS sequences on the chromosome. Some including the positions of each of the markers (A, B, C, and D) and state which of these markers would be transferred early?

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#Question id: 15617

#Unit 13. Methods in Biology

Wild type E. coli metabolizes the sugar lactose by expressing the enzyme ß-galactosidase. You have isolated a mutant that you call lac1–, which cannot synthesize ß-galactosidase and cannot grow on lactose (Lac–). During an condition you have a wild type (Lac+) strain carrying a Tn5 insertion known to be near several Lac genes on the E. coli chromosome. You grow P1 phage on this strain and use the resulting phage lysate to infect the lac1– strain, selecting for kanamycin resistance (Kanr). Among 100 Kanr transductants, you find that 82 are Lac– and 18 are Lac+. Express the distance between Tn5 and the lac1– mutation as a cotransduction frequency;

TLS Online TPP Program

#Question id: 15618

#Unit 13. Methods in Biology

Wild type E. coli metabolizes the sugar lactose by expressing the enzyme ß-galactosidase. You have isolated a mutant that you call lac1-, which cannot synthesize ß-galactosidase and cannot grow on lactose (Lac-). During an condition  isolate  a second Lac– mutation, which you designate lac2-. Using P1 phage on this strain and use the resulting phage lysate to infect the lac2- strain, selecting for   Kanr   transductants. In this case, all 100   Kanr   transductants that are examined are Lac–. What does this result tell you about the relationship between the lac1- and lac2- mutations?