Processes of Biotechnology MCQ Quiz in தமிழ் - Objective Question with Answer for Processes of Biotechnology - இலவச PDF ஐப் பதிவிறக்கவும்

Concept:

• In recombinant DNA technology, different lengths of DNA fragments are formed due to cleaving of DNA by restriction enzymes.
• These DNA fragments need to be sorted so that we can isolate our desired DNA fragment.
• The separation of DNA molecules is done by the process of agarose gel electrophoresis on the basis of their size only.

Explanation:

• The basic principle of electrophoresis is based on the fact that DNA is a negatively charged molecule.
• DNA molecules move towards an anode through the medium under an electric field.
• Agarose is a natural polymer obtained from algae and is commonly used as the medium in gel electrophoresis process.
• This medium provides a sieving effect by which DNA fragments move and get separated.
• Wells are made in the medium tray, where DNA is put.
• These wells are away from the anode end.
• The smaller fragments are lighter molecules and hence move faster towards the anode when electric field is applied.
• The larger molecules move slowly and remain away from the anode end.
• The DNA is stained with Ethidium bromide and appear as orange-coloured bands under UV rays.

Hence, the correct answer is option (2).

Concept:

• A plasmid is a circular extrachromosomal element.
• These are found in bacteria and some other organisms.
• Plasmids are capable of independent replication.
• Plasmids are comparatively smaller in size compared to host cell chromosomes.
• They exist in multiple copies within the host cell.
• Plasmids are used as vectors in recombinant DNA technology.
• E.g. - pBR322 is an example of a plasmid.

Explanation:

The features of a plasmid to serve as a vector in gene cloning experiments are:

• Origin of replication (ori): 
  • Replication of DNA (any foreign DNA inserted in the vector) begins at the ori.
  • Ori controls the copy number of the linked DNA.
  • Thus, to obtain a high copy number of inserted DNA, one needs to select a plasmid whose origin supports a high copy number.
  • Thus, "ori" is the most important feature in a plasmid to serve as a vector in a gene cloning experiment.
• Selectable marker genes:
  • Selectable marker genes are short sequences of DNA.
  • Once recombinant DNA is introduced into the target organism, the first step is to eliminate the bulk of non-transformed cells.
  • This is achieved by introducing a selectable marker gene.
  • Selectable marker genes like antibiotic resistance genes allow only the transformed cells to survive under selective conditions.
• Cloning sites:
  • Cloning sites are short sequences of DNA in a vector, where the DNA sequence to be cloned is inserted.
  • A cloning site consists of restriction sites that are recognized by restriction enzymes.
  • These enzymes cut the DNA so that foreign DNA can be inserted.

So according to the above information, the correct answer is option 1.

Concept:

• Genetic engineering or recombinant DNA technology is a technique of biotechnology that involves the joining of DNA molecules from different species.
• The DNA formed is called recombinant DNA.
• The plant or animal produced through genetic engineering contains genes usually from an unrelated organism.
• Genetic engineering involves the introduction of foreign DNA into an existing organism's cell with the help of vectors. This process is referred to as gene transfer.
• Gene transfer can take place either through the Indirect Method or Direct Method.

​

Explanation:

• Option 1: Ethidium bromide - INCORRECT
  • ​Ethidium bromide is used in gel electrophoresis.
  • Ethidium bromide is added to the buffer during DNA separation.
  • This is because ethidium bromide binds with DNA molecules during gel electrophoresis and on illumination, with UV light the DNA bands formed on the gel can be visualized.
• Option 2: 5-bromouridine - INCORRECT
  • 5-bromouridine is an analog of nucleoside uridine.
  • It is a uridine structure with bromo substituent at the 5th position.
  • It is a mutagen that causes base substitution in a DNA molecule. Thus causing damage to the DNA.
• Option 3: Polyethylene glycol - CORRECT
  • ​Chemicals like polyethylene glycol (PEG), polyvinyl alcohol and calcium phosphate are used to transfer DNA in genetic engineering.
  • It is a chemical method of gene transfer.
  • It helps enhance the uptake of DNA by plant protoplast during the production of a transgenic plant.
• Option 4: Polyacrylamide - INCORRECT
  • Polyacrylamide is used for protein separation.
  • For protein separation, polyacrylamide gel is used during electrophoresis. This electrophoresis is called PAGE (Polyacrylamide Gel Electrophoresis).
  • Since proteins are not negatively charged, they are first treated with a detergent called sodium dodecyl sulfate (SDS) before electrophoresis.
  • This makes the protein change into its linear form and also confers it with a negative charge.

So the correct answer is option 3 (Polyethylene glycol).

Concept:

• Genetic engineering or recombinant DNA technology is a technique of biotechnology that involves the joining of DNA molecules from different species.
• The DNA formed is called recombinant DNA.
• The plant or animal produced through genetic engineering contains genes usually from an unrelated organism.
• Genetic engineering involves the introduction of foreign DNA into an existing organism's cell with the help of vectors. This process is referred to as gene transfer.
• Gene transfer can take place either through the Indirect Method or Direct Method.

​

Explanation:

• Option 1: Ethidium bromide - INCORRECT
  • ​Ethidium bromide is used in gel electrophoresis.
  • Ethidium bromide is added to the buffer during DNA separation.
  • This is because ethidium bromide binds with DNA molecules during gel electrophoresis and on illumination, with UV light the DNA bands formed on the gel can be visualized.
• Option 2: 5-bromouridine - INCORRECT
  • 5-bromouridine is an analog of nucleoside uridine.
  • It is a uridine structure with bromo substituent at the 5th position.
  • It is a mutagen that causes base substitution in a DNA molecule. Thus causing damage to the DNA.
• Option 3: Polyethylene glycol - CORRECT
  • ​Chemicals like polyethylene glycol (PEG), polyvinyl alcohol and calcium phosphate are used to transfer DNA in genetic engineering.
  • It is a chemical method of gene transfer.
  • It helps enhance the uptake of DNA by plant protoplast during the production of a transgenic plant.
• Option 4: Polyacrylamide - INCORRECT
  • Polyacrylamide is used for protein separation.
  • For protein separation, polyacrylamide gel is used during electrophoresis. This electrophoresis is called PAGE (Polyacrylamide Gel Electrophoresis).
  • Since proteins are not negatively charged, they are first treated with a detergent called sodium dodecyl sulfate (SDS) before electrophoresis.
  • This makes the protein change into its linear form and also confers it with a negative charge.

So the correct answer is option 3 (Polyethylene glycol).

Concept:

• Restriction enzymes or restriction endonucleases are the enzymes that cut the phosphodiester bonds in the backbone of the DNA at specific sites. This produces DNA fragments with a known sequence.
• They cut the DNA molecule from within the segment.
• The recognition sites of restriction enzymes are palindromic i.e. the arrangement of nucleotides in these sites reads the same both in the forward (5' →3') direction and backward (3'→5') direction.
• E.g. - EcoRI is a restriction enzyme isolated from the bacterium Escherichia coli. Its recognition sequence is 

​5' - GAATTC - 3'
3' - CTTAAG - 5'

• Restriction enzymes are isolated from bacteria.

Explanation:

• Option 1: It recognizes a palindromic nucleotide sequence - CORRECT
  • ​The recognition sequence of any restriction enzyme is palindromic.
  • Hence it first recognizes a palindromic nucleotide sequence to cleave the DNA segment.
• Option 2: It is an endonuclease - CORRECT
  • ​Restriction enzymes are also known as restriction endonucleases.
  • Endonucleases cut the DNA molecule from within the DNA.
• Option 3: It is isolated from viruses - INCORRECT
  • ​Restriction enzymes are isolated from prokaryotes specifically bacteria.
  • Restriction enzymes are not isolated from the virus.
• Option 4: It can produce the same kind of sticky ends in different DNA molecules - CORRECT
  • ​When a restriction enzyme cuts any DNA molecule, it produces DNA fragments with the same kind of sticky ends.
  • These sticky ends can then be joined together with the help of an enzyme called DNA ligase.

​

So the correct answer is option 3.

Concept:

• PCR stands for Polymerase Chain Reaction.
• It is the process of amplifying or making multiple copies of a desired fragment of DNA.

Steps of PCR - 

1. Denaturation -
   • It is the process by which 2 strands of ds-DNA separates to form 2 single strands.
   • This is achieved by applying heat that helps in breaking the H-bonds between the 2 DNA strands.
2. Annealing -
   • In this process, 2 sets of primers bind to specific regions on the separated strands of DNA.
3. Extension -
   • This step involves extension of the primers using DNA polymerase in the presence of deoxynucleotides.

• These steps are repeated in cycles such that we get about a billion copies of the DNA in 30 cycles.

Explanation:

• Option 1: Herbert Boyer
  • In 1969, Herbert Boyer performed studies on restriction enzymes of the E. coli bacterium with especially useful properties.
  • Boyer observed that these enzymes have the capability of cutting DNA strands in a particular fashion i.e., DNA has ‘sticky ends’ on the strands.
  • These clipped ends made ligating the pieces of DNA a precise exercise.
  • Hence, this option is incorrect.
• Option 2: Har Gobind Khorana
  • In 1966, H. Gobind Khorana and his coworkers used long, artificial mRNA molecules containing only one nucleotide repeated continuously, or different nucleotides in repeating patterns.
  • The researchers added each artificial mRNA to ribosomes in a test tube and studied the sequence of amino acids in the polypeptide chain made by the ribosomes.
  • Khorana’s method, combined with the results of Nirenberg and Leder experiments, deciphered all the 64 codons in the dictionary of genetic code.
  • Nirenberg and Khorana received a Nobel Prize in 1968 for their research in solving the genetic code.
  • Hence, this option is incorrect.
• Option 3: Kary Mullis
  • He was an American biochemist who invented the PCR technique in 1983.
  • He received the Nobel prize in Chemistry in 1993.
  • Hence, this option is correct.
• Option 4: Arthur Kornberg
  • Arthur Kornberg, a prolific researcher discovered DNA polymerase, an enzyme critical to DNA replication.
  • For this discovery, Arthur Kornberg shared the 1959 Nobel Prize in Physiology or Medicine with Severo Ochoa, who discovered RNA polymerase.
  • Hence, this option is incorrect.

Hence, the correct answer is option (3).

Concept:

• Recombinant DNA technology is the technique of introducing a desirable gene into the target organism. It alters the genetic composition of the organism.
• A DNA fragment with the desired sequence of the gene from varying sources is introduced via a vector.
• In recombinant DNA technology or gene cloning, selectable marker genes are used for identifying the transformants.
• The tools used in recombinant DNA technology are restriction enzymes, DNA ligase, cloning vectors, competent hosts, etc.

Explanation:

DNA ligase - 

• DNA ligase is used in recombinant DNA technology for joining together DNA fragments.
• DNA ligase is an enzyme that forms the phosphodiester bond between two nucleotides of DNA.
• Thus the bond formed by a DNA ligase in the construction of a recombinant DNA molecule is between the 5' phosphate of one nucleotide and the 3'-OH group of the other nucleotide.
• DNA ligase can be used to join together DNA segments with sticky ends (cohesive ends) as well as blunt ends.
• DNA ligase can also be used to join DNA fragments from two different organisms that are cleaved by restriction enzymes.
• E.g. - DNA ligase obtained from bacteriophage T₄ is a universally used DNA ligase in recombinant DNA technology.

So, the correct answer is option 1.

Concept:

• A plasmid is a circular extrachromosomal element.
• These are found in bacteria and some other organisms.
• Plasmids are capable of independent replication.
• Plasmids are comparatively smaller in size compared to host cell chromosomes.
• They exist in multiple copies within the host cell.
• Plasmids are used as vectors in recombinant DNA technology.
• E.g. - pBR322 is an example of a plasmid.

Explanation:

The features of a plasmid to serve as a vector in gene cloning experiments are:

• Origin of replication (ori): 
  • Replication of DNA (any foreign DNA inserted in the vector) begins at the ori.
  • Ori controls the copy number of the linked DNA.
  • Thus, to obtain a high copy number of inserted DNA, one needs to select a plasmid whose origin supports a high copy number.
  • Thus, "ori" is the most important feature in a plasmid to serve as a vector in a gene cloning experiment.
• Selectable marker genes:
  • Selectable marker genes are short sequences of DNA.
  • Once recombinant DNA is introduced into the target organism, the first step is to eliminate the bulk of non-transformed cells.
  • This is achieved by introducing a selectable marker gene.
  • Selectable marker genes like antibiotic resistance genes allow only the transformed cells to survive under selective conditions.
• Cloning sites:
  • Cloning sites are short sequences of DNA in a vector, where the DNA sequence to be cloned is inserted.
  • A cloning site consists of restriction sites that are recognized by restriction enzymes.
  • These enzymes cut the DNA so that foreign DNA can be inserted.

So according to the above information, the correct answer is option 1.

Concept:

• PCR stands for Polymerase Chain Reaction.
• It is the process of amplifying or making multiple copies of a desired fragment of DNA.

Explanation:
The process involves 3 basic steps:

1. Denaturation -
   • It is the process by which 2 strands of ds-DNA separates to form 2 single strands.
   • This is achieved by applying heat that helps in breaking the H-bonds between the 2 DNA strands.
2. Annealing -
   • In this process, 2 sets of primers bind to specific regions on the separated strands of DNA.
   • Primers - are small, chemically synthesized oligonucleotides that are complimentary to specific regions of DNA.
3. Extension -
   • This step involves extension of the primers using Taq DNA polymerase in the presence of deoxynucleotides.
   • Taq polymerase is a thermostable DNA polymerase that is used for repeated amplification.
   • This enzyme remains active even in high temperatures because it is obtained from the bacteria Thermus aquaticus, which survives in extreme heat conditions like hot springs.

• These steps are repeated in cycles such that we get about a billion copies of the DNA in 30 cycles.

Therefore, we can see that Taq DNA polymerase catalyzes the extension of the primer end of the template DNA.