Processes of Biotechnology MCQ Quiz - Objective Question with Answer for Processes of Biotechnology - Download Free PDF

The correct answer is (A), (D), (E), (B), (C)

Concept:

Recombinant DNA technology involves several steps in specific sequence such as

• Isolation of DNA,
• Fragmentation of DNA by restriction endonucleases
• Isolation of a desired DNA fragment
• Ligation of the DNA fragment into a vector
• Transferring the recombinant DNA into the host
• Culturing the host cells in a medium at large scale
• Extraction of the desired product.

Explanation:

A. Isolation of desired DNA fragments: The first step is to isolate the DNA fragment that contains the gene of interest.

D. Ligation of DNA fragment into vector: The next step is to insert the isolated DNA fragment into a suitable vector (plasmid or viral vector).

E. Transferring of recombinant DNA to host: The recombinant vector is then introduced into a host cell, often a bacterial cell.

B. Culturing the host cells: The host cells containing the recombinant DNA are then cultured to produce many copies or express the gene of interest.

C. Extraction of desired product: Finally, the desired product (such as a protein) is extracted and purified from the cultured host cells.

The correct answer is (A) and (C) only

Explanation:

(A) Fragments of DNA can be separated by ELISA:

• This statement is incorrect.
• ELISA (Enzyme-Linked Immunosorbent Assay) is a technique used for detecting and quantifying proteins, peptides, antibodies, and hormones. It is not used for separating DNA fragments.
• DNA fragments are typically separated using techniques like gel electrophoresis.

(C) Recombinant DNA technology does not involve isolation of a desired DNA fragment:

• This statement is incorrect.
• Recombinant DNA technology involves multiple steps, including the isolation of the desired DNA fragment, its insertion into a vector, and its introduction into a host organism.
• Isolation of the desired DNA fragment is a crucial step in this process.

(B) Transformation is a procedure through which a piece of DNA is introduced in a host bacterium:

• This statement is correct. Transformation is a process by which foreign DNA is introduced into a bacterial cell, allowing the cell to express new genetic information.

(D) DNA ligases are used for stitching DNA fragments into a vector:

• This statement is correct.
• DNA ligases are enzymes that facilitate the joining of DNA strands together by catalyzing the formation of a phosphodiester bond, which is essential for inserting DNA fragments into vectors during cloning.

The correct option is 500 bp .

Concept:

• DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix.
• The most commonly used matrix is agarose which is a natural polymer extracted from sea weeds.
• The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel.
• Hence, the smaller the fragment size, the farther it moves.

Explanation:

• During agarose gel electrophoresis, DNA fragments are separated based on their size. Smaller DNA fragments migrate faster and thus move farther away from the wells than larger fragments.
• In this case:
  • The 100 bp fragment is the smallest and will migrate the furthest.
  • The 300 bp fragment is larger than the 100 bp fragment and will migrate a shorter distance compared to the 100 bp fragment.
  • The 500 bp fragment is the largest of the three and will migrate the shortest distance from the wells.

The correct answer is Gel electrophoresis

Explanation:

• Agarose is a polysaccharide extracted from seaweed, specifically from agar, which is widely used in molecular biology for gel electrophoresis.
• Gel electrophoresis is a technique used to separate DNA, RNA, or proteins based on their size and charge.
• Agarose gel provides a matrix through which molecules can migrate when an electric field is applied, allowing for the visualization and analysis of these molecules.
  • Tissue culture: This involves growing cells or tissues outside their natural environment under controlled conditions, typically using a nutrient medium. 
  • Gel electrophoresis: Agarose is extensively used in this technique to create a gel matrix through which nucleic acids or proteins are separated. Agarose gels are ideal for separating large molecules like DNA fragments.
  • Spectroscopy: This technique involves the interaction of light with matter to study the properties of substances.

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.
• A recombinant DNA molecule is produced by joining together two or more DNA segments. These DNA segments can be from two different organisms.
• The transformed cells in recombinant DNA technology are identified with the help of selectable marker genes like antibiotic resistance genes.

Explanation:

• Option 1: Restriction endonuclease - INCORRECT​
  • 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 at a specific site within a specific palindromic sequence.
  • Restriction endonucleases are used in the preparation of a recombinant DNA molecule to cleave the desired fragment of DNA.
• Option 2: DNA ligase - INCORRECT
  • DNA ligases catalyze the formation of phosphodiester bonds.
  • It is used in repairing single-strand breaks in a DNA molecule.
  • In the preparation of a recombinant DNA molecule, DNA ligase is used to join together DNA fragments.
• Option 3: DNA fragments - INCORRECT
  • In recombinant DNA technology, DNA fragments are produced by cutting DNA by restriction endonucleases.
  • These DNA fragments comprise the desired gene.
  • The DNA fragment is then inserted in the host cell for multiplication.
• Option 4: E. coli - CORRECT
  • E. coli is not required in the preparation of recombinant DNA molecule.
  • E. coli is widely used host organism in recombinant DNA technology.
  • However, it has no practical use in the making of the recombinant DNA molecule.
  • Once this molecule is prepared it is transferred in a host organism like E. coli for the multiplication of the desired gene.
  • Therefore, the E. coli is required after the formation of the recombinant DNA.

So the correct answer is option 1.

Correct answer: 3)

Concept:

• Gel electrophoresis is a method of separation of a mixture of DNA samples based on their molecular size and charge.
• Generally, agarose gel is used to carry out gel electrophoresis.

Explanation:

• Gel electrophoresis is carried out in a series of steps- agarose gel is prepared, a sample of DNA is prepared, then the mixture of DNA sample is loaded into the wells in the gel, and then an electric field is applied.
• On applying electric field DNA fragments start to move towards the positive terminal as they are negatively charged.
• This separates the sample based on size and charge.
• Ethidium bromide (EtBr) is a fluorescent dye and an intercalation agent used in gel electrophoresis.
• EtBr inserts itself in between the stacked bases. When visualized under the UV lamp, it will appear as bright orange bands.

​

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.
• This technique was developed by Kary Mullis in 1983.
• PCR is a cyclical technique where each cycle consists of 3 basic steps - 
  • Denaturation
  • Annealing
  • Extension

Explanation:

• Option 1: Denaturation of template DNA
  • 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.
  • This step does not require DNA polymerase and hence, this option is incorrect.
• Option 2: Annealing of primers to template DNA
  • 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.
  • This option is also incorrect.
• Option 3: Extension of primer end on the template DNA
  • 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.
  • Hence, this option is correct.
• Option 4: All of the above
  • This option is incorrect as only one of the above options is correct.

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 into the host cell.
• A vector or a cloning vector are vehicles that are used for transferring DNA from one cell to another.
• A vector needs to possess the following properties:
  • Should be able to replicate.
  • Should be a small DNA molecule that allows for easy isolation and handling.
  • Should contain selectable marker genes that will help to identify and isolate the transformants.
  • Should possess a site for the insertion of the desired DNA molecule.

Explanation:

• A selectable marker is a characteristic feature of the ideal vector.
• It is a required component during recombinant DNA technology as it is used to identify transformed and non-transformed cells.
• The genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli.
• For example, if we insert a DNA fragment within the tetracycline resistance gene of E. coli plasmid, there will be insertional inactivation of that gene.
• So, the transformed cell with the recombinant DNA will have only ampicillin resistance and not tetracycline resistance.
• We first grow the cells in a medium containing ampicillin where both transformed and non-transformed cells will form colonies.
• These colonies are then transferred to a medium containing tetracycline, where only the non-transformed cells will grow.
• Thus we can select the transformed colonies from the ampicillin medium.
• The tetracycline resistance gene in this case is called a selectable marker. 

So from the above-given information, the correct answer is option 2.

Additional Information

Competent bacterial cell:

• Cell competence refers to a cell's ability to take up genetic material from its surroundings.
• A bacterial cell can be made competent by the heat-shock method, by which pores are created in the cell wall through which DNA can enter the bacterial cell.

Recombinant bacterial cell:

• A recombinant bacterial cell refers to a cell wherein its genetic constituent has undergone recombination.
• This genetic recombination is due to the DNA transfer that has taken place from a donor cell.
• The transfer of genetic material can take place either due to transformation, transduction or conjugation.

Concept:

• Agarose gel electrophoresis separates DNA molecules based on their size.
• The basic principle of this process 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.

Explanation:

• Option 1: DNA can be seen in visible light
  • Pure DNA cannot be seen in visible light.
  • Hence, this option is incorrect.
• Option 2: DNA can be seen without staining in visible light
  • DNA can only be seen after staining.
  • Hence, this option is incorrect.
• Option 3: Ethidium bromide stained DNA can be seen in visible light
  • Ethidium bromide is a fluorescent dye that can be viewed only under UV light.
  • Hence, this option is incorrect.
• Option 4: Ethidium bromide stained DNA can be seen under exposure to UV light
  • Pure DNA is stained with Ethidium bromide and then viewed under UV light.
  • The DNA fragments are visible as orange-coloured bands in the agarose gel under UV light.
  • Hence, this option is correct.

Hence, the correct answer is option (4).

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.
• A recombinant DNA molecule is produced by joining together two or more DNA segments. These DNA segments can be from two different organisms.
• The transformed cells in recombinant DNA technology are identified with the help of selectable marker genes like antibiotic resistance genes.

Explanation:

• Option 1: Restriction endonuclease - INCORRECT​
  • 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 at a specific site within a specific palindromic sequence.
  • Restriction endonucleases are used in the preparation of a recombinant DNA molecule to cleave the desired fragment of DNA.
• Option 2: DNA ligase - INCORRECT
  • DNA ligases catalyze the formation of phosphodiester bonds.
  • It is used in repairing single-strand breaks in a DNA molecule.
  • In the preparation of a recombinant DNA molecule, DNA ligase is used to join together DNA fragments.
• Option 3: DNA fragments - INCORRECT
  • In recombinant DNA technology, DNA fragments are produced by cutting DNA by restriction endonucleases.
  • These DNA fragments comprise the desired gene.
  • The DNA fragment is then inserted in the host cell for multiplication.
• Option 4: E. coli - CORRECT
  • E. coli is not required in the preparation of recombinant DNA molecule.
  • E. coli is widely used host organism in recombinant DNA technology.
  • However, it has no practical use in the making of the recombinant DNA molecule.
  • Once this molecule is prepared it is transferred in a host organism like E. coli for the multiplication of the desired gene.
  • Therefore, the E. coli is required after the formation of the recombinant DNA.

So the correct answer is option 4.

Concept:

• A cloning vector is a DNA molecule that acts as a vehicle to carry the gene of interest.
• They carry the gene of interest into the host cell during the process of cloning.
• The most common cloning vectors are plasmids, bacteriophages, cosmids, etc.

Explanation:

• There are certain characteristics of a desirable vector used in gene cloning experiments.
• Vector molecules should have a single recognition site.
• This will help in easy ligation of the gene of interest at one specific location.
• Multiple recognition sites will cut vector molecules at more than one position, leading to undesirable ligation of genes at multiple positions.
• The vector should have the origin of replication so that it can replicate inside the host cell independently.
• Should have selectable markers to identify the recombinants and non-recombinants.
• Should have a single restriction enzyme site to cut the vector molecule at a specific location.

So, the correct answer is option 1.

Concept:

• RNAi or RNA interference is a regulatory system occurring in eukaryotic cells.
• It helps in regulating the activity of the genes by silencing or deactivating the genes.
• It is a post-transcriptional process, that inhibits the translation of mRNA into its proteins.

Important Points

• RNAi is a genetic mechanism in eukaryotes that is initiated by a double-stranded RNA (dsRNA) molecule.
• The eukaryotic genome encodes a special RNA molecule called miRNA (micro RNA). Each miRNA is produced from a pre-miRNA (precursor transcript of miRNA).
• pre-miRNA is cleaved by the DICER enzyme to release miRNA.
• Once cleaved, the mature miRNA binds to the RNA-induced silencing complex (RISC).
• RISC contains enzymes like ribonuclease that cleave the specific segments of mRNA.
• The miRNA-RISC complex then binds to the complementary strand of mRNA.
• Once the two strands bind, the complex enzymatically cleaves the target sites on mRNA.
• This in turn inhibits the translation of the cleaved site of mRNA into proteins and thus the corresponding genes are silenced.
• Applications of RNAi:
  • RNAi helps in the regulation of genes.
  • RNAi mediates cellular defense against viruses.
  • RNAi helps in the treatment of diseases of bacterial or parasitic origin.
  • It is also employed in the treatment of genetic diseases and tumors.

• Thus from the above-given information, RNA interference is initiated by double-stranded RNA (ds RNA).

Hence, the correct answer is option 1 (ds RNA).

Concept:

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

Important PointsSteps 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 at 90-95°C, that helps in breaking the H-bonds between the 2 DNA strands.
2. Primer Annealing -
   • In this process, the temperature is brought down to 50-55ºC, such that 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. Primer 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 active at around 72°C and 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, the correct sequence of PCR is Denaturation → Primer annealing → DNA synthesis.

Concept:

• In recombinant DNA (rDNA) technology, the aim is to produce a desirable protein product.
• In order to obtain the protein, the rDNA needs to be expressed.
• The host cells must be induced to express the foreign gene by providing appropriate conditions.
• This would provide us with the recombinant protein, produced by a heterologous host.
• Heterologous host refers to the host cell that produces the protein in a cell line where it is not supposed to be.
• The recombinant proteins can be extracted and purified using various separation techniques in the laboratory.
• But this kind of laboratory set-up would only give a small-scale production.
• Large scale production is carried out in bioreactors that use a continuous culture system.

Explanation:

• A continuous culture system is where used medium is removed from one side while fresh medium is added from other side.
• This necessitates the presence of in-lets and out-lets.
• This system helps in maintaining the cells in the exponential phase of growth.
• This gives us a higher yield of the desired protein due to the larger biomass produced.
• In a typical bioreactor with a continuous culture system, 100-1000L of cultures can be processed.

Hence, the correct answer is option (3).

Additional InformationStirred-type Bioreactors - 

• It may be of 2 types:
  • A simple stirred-tank bioreactor that comes with a stirrer to mix the contents evenly and facilitate oxygen availability throughout the reactor.
  • A sparged stirred-tank bioreactor that uses sterile air bubbles to increase the surface area for oxygen transfer.
• They also consist of in-lets and out-lets for maintaining a continuous culture system.

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 and at a specific site.
• The recognition sites of restriction endonucleases 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.
• Restriction endonucleases are isolated from bacteria.

Explanation:

Option 1: Haemophilus influenzae - INCORRECT

• ​Haemophilus influenzae is a source of restriction endonuclease.
• Hind III is a restriction endonuclease isolated from Haemophilus influenzae.
• The recognition sequence of Hind III is:
• ​

• ​Escherichia coli is a source of restriction endonuclease.
• EcoRI is a restriction endonuclease isolated from Escherichia coli.
• The recognition sequence of EcoRI is:

​  Option 3: Entamoeba coli - CORRECT​Entamoeba coli is not a source of any restriction endonucleases.

• It is a non-pathogenic protozoa, mostly present in the human gut.

• ​Bacillus amyloliquefaciens is a source of restriction endonuclease.
• BamHI is a restriction endonuclease isolated from Bacillus amyloliquefaciens.
• The recognition site of BamHI is:
• ​