Biotechnology: Principles & Processes - 2 - Free MCQ Practice Test

Phage or Bacteriophage is a virus that infects bacteria. Such viruses transfer their genetic materials into host bacteria and using the bacterial machinery increase in number and multiply rapidly to kill host cells.

Plasmid is a small DNA molecule within a cell that is physically separated from a chromosomal DNA and can replicate independently. Plasmid is most commonly found in bacteria as small circular, double stranded DNA molecule.

In this technique,  the desired DNA is linked to the virus or plasmid to make the multiple copy of desire substance in host body.

Restriction enzymes belongs to a larger class of enzymes called nucleases. Which are of two kinds endonucleases and exonucleases.

The enzyme nuclease acts on nucleic acid DNA and RNA. This enzyme is used to hydrolyze nucleic acid.

Primers are chemically synthesized oligonucleotides that are complementary to the regions of DNA and the enzyme DNA polymerase.

Downstream processing is the separation and purification of recombinant protein product. Downstream processing and quality control testing vary for different products

Gel electrophoresis technique involves separation of different segments of DNA according to their size. The smallest bands in the agarose gel will be towards positively charged anode.

If the process of replication ‘of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a thermophilic bacterium Thermits aquaticus), which is active during the high temperature induced denaturation of double stranded DNA.

Option (b) is the correct answer because when restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands, then single stranded portions are left at the ends. These overhanging stretches on each strand are called sticky ends.

Option (1) is the correct answer because separation of DNA fragments which is carried out after restriction enzyme digestion, is done by a technique known as gel electrophoresis.

Option (2) is not the correct answer because polymerase chain reaction (PCR) is a technique used for amplification of gene of interest.

Option (3) is not the correct answer because recombinant DNA technology comprises altering genetic material outside an organism to obtain enhanced and desired characteristics in living organisms or as their products.

Option (4) is not the answer because Southern blotting is a method used for detection of specific DNA sequences in samples.

Option (3) is the correct answer because cellulase is used to isolate genetic material from plant cells and chitinase is used to isolate genetic material from fungal cells.

Option (2) is incorrect because protease is used for digestion of proteins.

Option (1) and (4) are incorrect because lipase is used for the breakdown of lipids.

Both the statements are correct but the given reason is not the correct explanation. Polymerase chain reaction is used in DNA amplification.

Ampicillin resistance gene is a selectable marker that helps to check transformation by selection of transformants.

The correct sequences of process of recombinant DNA technology are Isolation of DNA, fragmentation of DNA by restriction endonuclease, isolation of desired DNA fragment, ligation of DNA fragment into vector, transferring of into host and culturing in host cell to get desired product.

Option (a) is the correct answer because both the statements I and II are correct. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. It will bind to the DNA and cut each of the two strands of double helix at specific points. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome site; but between the same two bases on the opposite strands. So both the statements I and II are correct.

The sequence of the 5’ and 3’ primers for the given DNA sequence will be 5’ AATGC 3’, 5’ GACTC 3’. In primer design, the forward primer is derived directly from the start of the DNA sequence, which is 5’ AATGC 3’. The reverse primer is complementary to the end of the sequence, considering the antiparallel nature of DNA, resulting in 5’ GACTC 3’. This follows the standard method for designing primers, as discussed in PCR techniques and DNA replication processes.

Option (d) is the correct answer. Cloning vectors are the carriers of the desired gene in the host cell. The features desirable in a cloning vector are :-

• Presence of origin of replication
• Presence of marker genes
• Presence of very few, preferably single recognition site for the commonly used restriction enzymes

The agarose gel with high percentage of agar will lead to accumulation of large sized DNA fragments near the wells as pore size is small near the well.

Various enzymes like protease, RNase, etc. are added to break down substances like proteins, RNA, etc. Once all these substances are broken down, DNA is left which is precipitated out by adding chilled ethanol.

Ethanol has a lower dielectric constant than water, making it to promote ionic bond formation the Na⁺ (from the salt) and the PO⁻₃ (from the DNA backbone), further, causing the DNA to precipitate.

- The Assertion (A) is true because ethidium bromide binds to DNA and is necessary for visualization during gel electrophoresis.

- The Reason (R) is false because ethidium bromide requires UV radiation to visualize DNA; it does not make DNA visible under normal light conditions.

- Therefore, the Reason is not the correct explanation of the Assertion, as the Assertion is true but the Reason is false.