14. White colonies indicate the insertion of foreign DNA within the polylinker s
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14. White colonies indicate the insertion of foreign DNA within the polylinker site of the plasmid vector, disrupting the lacz gene. A. True B. False 15. What is the advantage to producing a genomic library using phages instead of plasmids? A Phage particle holds a much larger insert of foreign DNA B. Phage particle holds more inserts of foreign DNA C. Phage particle needs no bacterial host D. Phage particle produces a plaque E. All of the above 16. What's the main reason to covert mRNA to cDNA molecules in molecular cloning? A. DNA is more stable B. DNA is more catalytic C. mRNA is difficult to extract D. mRNA is easily contaminated E. All of the above 17. Which of the following processes is commonly used to introduce recombinant DNA molecules into eukaryotic hosts? A. Binary fission B. Conjugation C. Transduction D. Transfection E. Transformation 18. Which of the following processes uses a brief electric pulse to induce the formation of transient pores in the phospholipid bilayers? A. Electroporation B. Gene gun C. Microinjection D. Shuttle vectors E. Viral vectors 19. Which of the following methods is often used in gene therapy? A. Electroporation B. Gene gun C. Microinjection D. Shuttle vectors E. Viral vectors 20. It is generally easier to introduce recombinant DNA into prokaryotic cells than into eukaryotic cells. A. TrueExplanation / Answer
14. a] True
The blue-white screen is a screening technique that allows for the rapid and convenient detection of recombinant bacteria in vector-based molecular cloning experiments. DNA of interest is ligated into a vector. The vector is then inserted into competent host cells viable for transformation, which are then grown in the presence of X-gal. Cells transformed with vectors containing recombinant DNA will produce white colonies; cells transformed with non-recombinant plasmids (i.e. only the vector) grow into blue colonies. This method of screening is usually performed using a suitable bacterial strain, but other organisms such as yeast may also be used.
15.a] phage holds much larger inserts of foreign DNA
Phage ? is a double-stranded DNA virus that infects E. coli. The ? chromosome is 48.5kb long and can carry inserts up to 25kb. These inserts replace non-essential viral sequences in the ? chromosome, while the genes required for formation of viral particles and infection remain intact. The insert DNA is replicated with the viral DNA; thus, together they are packaged into viral particles. These particles are very efficient at infection and multiplication leading to a higher production of the recombinant ? chromosomes. However, due to the smaller insert size, libraries made with ? phage may require many clones for full genome coverage.
17. C] Transduction
Genetic transduction is the transfer of DNA from a virus to its bacterial or eukaryotic host cell. Transduction with viral vectors is a common method for gene delivery.
18. A. Electroporation
Electroporation, or electropermeabilization, is a microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, or DNA to be introduced into the cell.
19. E.Viral vectors
A gene that is inserted directly into a cell usually does not function. Instead, a carrier called a vector is genetically engineered to deliver the gene. Certain viruses are often used as vectors because they can deliver the new gene by infecting the cell.
20. True
The genomes of eukaryotes are larger and more complex than those of bacteria, so modifications of the techniques are needed to handle the larger amounts of DNA and the array of different cells and life cycles of eukaryotes.
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