Suppose the experiment of Meselson and Stahl was performed on a sample of 8 cells, each containing one copy of its circular double-stranded DNA genome, and that had been growing on normal   14N medium. You then grew the cells for 3 generations in medium containing   15N. The outcome would be             A)   8 cells with single-stranded DNA molecules with   14N, and 24 cells with single-stranded DNA molecules with   15N.                 B)   16 cells with double-stranded DNA molecules with equal amounts of   14N and   15N, and 48 cells with double-stranded DNA molecules with   15N.             C)   8 cells with double-stranded DNA molecules with equal amounts of   14N and   15N, and 24 cells with double-stranded DNA molecules with   15N.             D)   8 cells with double-stranded DNA molecules with equal amounts of   14N and   15N, and 32 cells with double-stranded DNA molecules with   15N.             E)   65 cells with single-stranded DNA molecules with   15N.

Would you expect transfer of chromosomal DNA by conjugation to be more efficient if cells were plated together on solid medium (agar) or mixed together in a liquid in a shaking flask? Explain.

Suppose one were provided with an actively dividing culture of E. coli to which radioactive thymine had been added. What would happen if a cell replicated once in the presence of the radioactive base? (a) one of the daughter cells, but not the other would have radioactive DNA (b) neither of the two daughter cells would be radioactive (c) only the purines of the DNA would be radioactive (d) radioactive thymine would pair with radioactive guanine (e ) DNA in both daughter cells would be radioactive

In a hypothetical scenario, you wake up one morning to your roommate exclaiming about her sudden hair growth. She has been supplementing her diet with a strange new fungus purchased at the local farmer’s market. You take samples of the fungus to your lab and you find that this fungus does indeed make a protein (the harE protein) that stimulates hair growth. You construct a fungal genomic DNA library in E. Coli with the hope of cloning the harE gene. If you succeed you will be a billionaire! You obtain DNA from the fungus, digest it with a restriction enzyme, and clone it into a vector. b) You clone your digested genomic DNA into this vector. The E. coli (bacteria) cells that you will transform to create your library will have what phenotype prior to transformation?c) How do you distinguish bacterial cells that carry a vector from those that do not?d) How do you distinguish bacterial cells that carry a recombinant vector from those that carry the original cloning vector?

You have ligated a foreign DNA fragment into the EcoRI site in multiple cloning site of pUCI18. You then transform how E.coli with the ligation mixture. Some of the bacterial colonies growing on the nutrient agar plate that contains ampicillin and Xgal are white and some are blue. Bacterial colonies that are white a) contain recombinant plasmid DNA b) have hydrolyzed ampicillin to form a colored compound c) are untransformed bacteria d) contain non recombinant plasmid DNA

When cloning a piece of DNA, the purpose of using the LacZ blue-white colony method is to A) Remove bacteria that do not have recombinant vectors B) Remove bacteria that do not have the DNA insert of interest Remove linear DNA Distinguish colonies that have recombinant vectors from those with non-recombinant vectors. E) Remove bacteria that have not taken up the vector

What is the role of the liquid detergent used in the experiment?  a) It allows the DNA to unwind. b) It aids filtration. c) It helps break down the cell membrane. d) It helps keep the DNA soluble in solution.

You isolated two bacteria from soil that you assumed were different species since they have different properties - for example, one is resistant to several antibiotics and the other is not. However, upon sequencing the 16S rRNA genes of the isolates, you have discovered that they are the same genus and species. When you extract the total DNA from each and run a gel, you discover the resistant strain has a plasmid in addition to the primary Chromosome. a. How might this strain have acquired the plasmid? b. What is definitely encoded on the plasmid given the information provided? c. How could you use fluorescence microscopy to determine if other bacteria in your soil suspension are carrying the same plasmid? Be sure to comment on the type of fluorescent probe, how it will interact with your sample, and how you will distinguish cells harboring the plasmid from the rest of the population (what will it look like).

We transformed E coli cells with a plasmid modified to contain a ‘virulence factor’ which would allow growth on media containing the antibiotic kanamycin (Kan). The plasmid confers constitutive resistance to ampicillin (Amp). Assume you were given competent cells of known transformation efficiency (TE).  Assume TE= 1x10[7] (note 10[7] means 10 to the power of 7). You want to have about 1000 colonies on the P-200 plate. How many nanograms of plasmid should you use in the transformation reaction? Select only one answer.   1. 0.05   2. 20.00   3. 0.50   4. 50.00   5. 200.00   6. 5.00

you have transformed E.coli cells with a plasmid containing the gene for the enzyme beta-lactamase you have used 3µl of a stock solution of 2.5ng/µl DNA. You transformed 150/µl of competent cells, using the calcium chloride method. you have added 600µl of luria broth to the cells and then plated out 200µl on triplicate plates. upon counting the colonies, you got the following results: plate 1: 120 cfu plate 2: 35 cfu plate 3: 95 cfu please answer the following question: 1. what new characteristic will the cells have ater transformation? 2. how are you going to test for the new characteristic? 3. calculate the transformation efficiency of the experiment?