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Biotechnology Principles and Processes Test - 48

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Biotechnology Principles and Processes Test - 48
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  • Question 1
    1 / -0
    Which one is a true statement regarding $$DNA$$ polymerase used in $$PCR$$
    Solution
    Taq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Chien et al. in 1976. Its name is often abbreviated to Taq Pol or simply Taq. It is frequently used in the polymerase chain reaction (PCR), a method for greatly amplifying the quantity of short segments of DNA.

    T. aquaticus is a bacterium that lives in hot springs and hydrothermal vents, and Taq polymerase was identified as an enzyme able to withstand the protein-denaturing conditions (high temperature) required during PCR. Therefore, it replaced the DNA polymerase from E. coli originally used in PCR. Taq's optimum temperature for activity is 75–80 °C, with a half-life of greater than 2 hours at 92.5 °C, 40 minutes at 95 °C and 9 minutes at 97.5 °C, and can replicate a 1000 base pair strand of DNA in less than 10 seconds at 72 °C.

    So the correct option is 'it remains active at high temperature'.
  • Question 2
    1 / -0
    How many linear DNA fragments will be produced when a circular plasmid is digested with a restriction enzyme having 3 sites?
    Solution
    Restriction enzymes are DNA-cutting enzymes. Each enzyme recognizes one or a few target sequences and cuts DNA at or near those sequences. Many restriction enzymes make staggered cuts, producing ends with single-stranded DNA overhangs. However, some produce blunt ends.
    Restriction enzymes are found in bacteria (and other prokaryotes). They recognize and bind to specific sequences of DNA, called restriction sites. Each restriction enzyme recognizes just one or a few restriction sites. When it finds its target sequence, a restriction enzyme will make a double-stranded cut in the DNA molecule.
    In DNA cloning, researchers make many copies of a piece of DNA, such as a gene. In many cases, cloning involves inserting the gene into a piece of circular DNA called a plasmid, which can be copied in bacteria.
    If the plasmid has 3 recognition sequences for a given restriction endonuclease, then 4 linear DNA fragments are obtained because, if the DNA is linear then the number of fragments obtained is (N+1) whereas if the DNA is circular then the number of fragments obtained will be N for N recognition sequences for the given restriction endonuclease in a plasmid.
    So the correct option is '4'.
  • Question 3
    1 / -0
    Which of the following is not a component of downstreaming processing?
    Solution
    A widely recognized heuristic for categorizing downstream processing operations divides them into four groups which are applied in order to bring a product from its natural state as a component of a tissue, cell or fermentation broth through progressive improvements in purity and concentration.

    Removal of insolubles is the first step and involves the capture of the product as a solute in a particulate-free liquid, for example the separation of cells, cell debris or other particulate matter from fermentation broth containing an antibiotic. Typical operations to achieve this are filtration, centrifugation, sedimentation, precipitation, flocculation, electro-precipitation, and gravity settling. Additional operations such as grinding, homogenization, or leaching, required to recover products from solid sources such as plant and animal tissues, are usually included in this group.

    Product isolation is the removal of those components whose properties vary considerably from that of the desired product. For most products, water is the chief impurity and isolation steps are designed to remove most of it, reducing the volume of material to be handled and concentrating the product. Solvent extraction, adsorption, ultrafiltration, and precipitation are some of the unit operations involved.

    Product purification is done to separate those contaminants that resemble the product very closely in physical and chemical properties. Consequently steps in this stage are expensive to carry out and require sensitive and sophisticated equipment. This stage contributes a significant fraction of the entire downstream processing expenditure. Examples of operations include affinity, size exclusion, reversed phase chromatography, ion-exchange chromatography, crystallization and fractional precipitation.

    Product polishing describes the final processing steps which end with packaging of the product in a form that is stable, easily transportable and convenient. Crystallization, desiccation, lyophilization and spray drying are typical unit operations. Depending on the product and its intended use, polishing may also include operations to sterilize the product and remove or deactivate trace contaminants which might compromise product safety. Such operations might include the removal of viruses or depyrogenation.

    So the correct option is 'Expression'.
  • Question 4
    1 / -0
    The taq polymerase enzyme is obtained from
    Solution
    Taq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Chien et al. in 1976. Its name is often abbreviated to Taq Pol or simply Taq. It is frequently used in the polymerase chain reaction (PCR), a method for greatly amplifying the quantity of short segments of DNA.

    T. aquaticus is a bacterium that lives in hot springs and hydrothermal vents, and Taq polymerase was identified as an enzyme able to withstand the protein-denaturing conditions (high temperature) required during PCR. Therefore, it replaced the DNA polymerase from E. coli originally used in PCR. Taq's optimum temperature for activity is 75–80 °C, with a half-life of greater than 2 hours at 92.5 °C, 40 minutes at 95 °C and 9 minutes at 97.5 °C, and can replicate a 1000 base pair strand of DNA in less than 10 seconds at 72 °C.

    So the correct option is 'Thermus aquaticus'.
  • Question 5
    1 / -0
    $$Eco \,RI$$ cleaves the $$DNA$$ strands to produce
    Solution
    EcoRI is a restriction endonuclease enzyme isolated from species E. coli. The Eco part of the enzyme's name originates from the species from which it was isolated, while the R represents the particular strain, in this case RY13. The last part of its name, the I, denotes that it was the first enzyme isolated from this strain. EcoRI is a restriction enzyme that cleaves DNA double helices into fragments at specific sites. It is also a part of the restriction modification system.

    In molecular biology it is used as a restriction enzyme. EcoRI creates 4 nucleotide sticky ends with 5' end overhangs of AATT. The nucleic acid recognition sequence where the enzyme cuts is G/AATTC, which has a palindromic, complementary sequence of CTTAA/G. The / in the sequence indicates which phosphodiester bond the enzyme will break in the DNA molecule. 

    So the correct option is 'sticky ends'.
  • Question 6
    1 / -0
    How many copies of the DNA sample are produced in PCR technique after 6-cycle?
    Solution
    Polymerase chain reaction (PCR) is a technique that exponentially amplifies a single copy of a specific DNA segment. It generates thousands of copies of that specific DNA segment. After completion of one cycle, 2 copies are produced from a single DNA segment. After completion of the second cycle, 2$$^2$$ = 4 copies are produced. Similarly, after n$$^{th}$$ cycle, 2$$^2$$ copies are produced, where n is the number of cycles. Hence, after completion of 6 cycle, 2$$^6$$ = 64 copies will be produced. 
    Thus, the correct answer is '64.'
  • Question 7
    1 / -0
    The cutting of DNA at specific locations became possible with the discovery of
    Solution
    A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within the molecule known as restriction sites. Restrictions enzymes are one class of the broader endonuclease group of enzymes. Restriction enzymes are commonly classified into five types, which differ in their structure and whether they cut their DNA substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.

    So the correct option is 'Restriction Enzymes'.
  • Question 8
    1 / -0
    Which of the following restriction enzymes produces blunt ends?
    Solution
    A. Sal I is a restriction endonuclease isolated from Streptomyces albus. It produces sticky ends by making the cut in the nucleotide sequence G/TCGAC
    B. Eco RV is type II restriction endonuclease isolated from Escherichia coli which produces blunt ends by making a cut in the center of the nucleotide sequence GAT/ATC.
    C. Xho is a restriction endonuclease isolated from Xanthomonas campestris. It produces sticky ends by making a cut in the recognition sequence C/TCGAG.
    D. Hind III is a type II restriction enzyme isolated from Haemophilus influenzae. It produces sticky ends by making a cut in the nucleotide sequence A/AGCTT.
    (Note: '/' denotes the position where the restriction enzyme is making cut in the nucleotide sequence).

    So, the correct answer is 'Eco RV'.
  • Question 9
    1 / -0
    In reference to DNA polymerase III, which statement is wrong?
    Solution
    Like DNA replication in an organism, PCR requires a DNA polymerase enzyme that makes new strands of DNA, using existing strands as templates. The DNA polymerase typically used in PCR is called Taq polymerase, after the heat-tolerant bacterium from which it was isolated (Thermus aquaticus).
    So, the correct option is 'Required for PCR'.
  • Question 10
    1 / -0
    Which enzyme is required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology?
    Solution
    The alkaline phosphatase enzyme is required to prevent unwanted self-ligation of vector DNA molecules in procedures of rDNA (recombinant DNA) technology during the cloning process. 
    Alkaline phosphatase removes the terminal 5'-phosphate group. Since ligation absolutely requires a 5'-phosphate group at the site of the nick, the vector DNA cannot be self-ligated in the absence of this group.

    So, the correct option is 'Alkaline phosphatase'.
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