When using a conventional plasmid cloning vector containing a b-galactosidase gene, it is possible to perform a "blue-white screen" to determine which bacteria have taken up a plasmid into which a DNA fragment as been inserted, as opposed to those that have taken up just reclosed plasmid vector, by growing the transformed cells on nutrient agar plates containing the artificial b-gal substrate X-gal. Will bacteria that have taken up a plasmid into which a DNA fragment has been inserted form a blue colony or a white colony when grown on this medium? Briefly explain why these bacteria would form a colony of the color you chose.

In the following "gene library" cloning experiment Digested genomic DNA AmpR gene TCR gene TCR is tetracycline resistant marker, AmpR is ampicillin resistant marker and BamHI is the unique restriction enzyme on plasmid. A PhD student digests/cuts the plasmids with BamHI restriction enzyme and the genomic DNA with EcoRI restriction enzyme. After performing the cloning experiment and obtaining colonies on a selection plate, the obtained cells will be ..... (Hint: this question is even more challenging; the PhD student was later demoted to an MSc student). a) resistant to ampicillin and tetracycline b) sensitive to tetracycline and ampicillin c) resistant to tetracycline and sensitive to ampicillin d) resistant to ampicillin and sensitive to tetracycline e) sensitive to ampicillin and tetracycline BamHI

Explain why rolling circle replication of plasmids is semi-conservative.

Briefly explain the role of arabinose in the expression of the GFP gene of the pGLO plasmid.

Assume you have successfully cloned a small (200 bp) fragment of DNA into the polylinker region of a pUC18 cloning vector. Describe the appearance of transformed colonies you would expect to see on each of the following plates: plain media, media containing ampicillin, media containing tetracycline, media containing ampicillin and X-Gal.

A plasmid has been modified such that it carries the gene for beta-galactosidase (lacZ) under the control of the lac promoter. Between the lac promoter and the lacZ gene is an empty multiple cloning site (MSC). This plasmid also carries ampicillin resistance. E. coli are transformed with this plasmid, and grown on nutrient agar containing ampicillin, IPTG, and the lactose analogue Xgal for 18 hours. Following incubation, the plates are examined. What will be the likely colour of the bacteria colonies?

a. Bacteriophage P22 was used in generalized transduction experiments to infect the Salmonella typhimurium donor strains described in the table below. The resulting phage lysates were then used to infect the S. typhimurium recipient strains listed in the table. In each cross, a phenotype was selected for one of the three genetic markers studied (str, aceA, thrA), and then replicates were performed to select the corresponding recombinants for the other two markers. The results are given in the following table: Recipient strain Selected phenotype Selected recombinants Donor strain str thrA aceAt thrA str aceA+ strs thrA+ aceA thrA+ str aceA Str Ace+ Str ThrA ThrA+ ThrA ThrA+ Ace Ace+ str: gene involved in streptomycin resistance, aceA: gene involved in the use of acetate as a carbon source, thrA: gene involved in the biosynthesis of threonine. Number 60 40 95 5 10 90 What are the selective media used in these three transduction experiments, on the one hand to obtain the selected…