Process of Recombinant DNA technology Questions in English

(C) The $PCR$ process consists of three main steps: $1$. Denaturation,$2$. Annealing,and $3$. Extension.
$Taq$ polymerase is a thermostable $DNA$ polymerase enzyme.
It catalyzes the addition of nucleotides to the $3'$ end of the primers,which is known as the extension step.
Denaturation is caused by high temperature,and annealing involves the binding of primers to the template $DNA$.

(C) The method described is known as Biolistics or the gene gun method.
In this technique,cells are bombarded with high-velocity microparticles of gold or tungsten coated with $DNA$.
Protoplast fusion involves the fusion of two or more protoplasts,either spontaneously or in the presence of fusion-inducing chemicals like polyethylene glycol $(PEG)$.
Transfection refers to the process of deliberately introducing naked or purified nucleic acids (like $DNA$) into eukaryotic cells.

(C) $Spooling$ is a technique used to collect the precipitated $DNA$ by winding it onto a glass rod at the final stage of $DNA$ extraction.
$Elution$ refers to the process of extracting separated $DNA$ fragments from an agarose gel.
$Gel \; electrophoresis$ is a laboratory method used to separate and analyze macromolecules (like $DNA$,$RNA$,or proteins) based on their size using a gel matrix.
$PCR$ $(Polymerase \; Chain \; Reaction)$ is a technique used to amplify a specific segment of $DNA$.

(C) In the Polymerase Chain Reaction $(PCR)$,the extension or polymerisation step is carried out by the enzyme $Taq$ $DNA$ polymerase.
The optimum temperature for the activity of $Taq$ $DNA$ polymerase is $72^{\circ}C$.
This enzyme is isolated from the thermophilic bacterium $Thermus$ $aquaticus$,which allows it to remain stable and active even at high temperatures,tolerating temperatures up to $95^{\circ}C$ (the denaturation temperature).
Therefore,the correct values are $72^{\circ}C$ for polymerisation and $95^{\circ}C$ for enzyme tolerance.

(B) stirred-tank bioreactor is designed to provide optimal growth conditions for cells or microorganisms. The primary function of the stirrer (impeller) is to ensure uniform mixing of the culture medium and to facilitate aeration by dispersing air bubbles throughout the vessel. While bioreactors have separate systems for temperature control,foam control,and pH regulation,the stirrer specifically aids in the homogenization of the contents and the distribution of oxygen.

(A) The process of biotechnology is divided into two main stages: Upstream processing and Downstream processing.
$1$. Upstream processing involves the preparation of the biological agent,optimization of growth conditions,and the actual fermentation process in a bioreactor.
$2$. Downstream processing refers to the stage after the completion of the biosynthetic phase (fermentation). It involves the separation and purification of the desired product,followed by formulation and quality control testing.
Therefore,the separation and purification of the desired compound produced in a bioreactor is a part of downstream processing.

(D) Gel electrophoresis is a technique used for the separation and analysis of macromolecules (such as $DNA$,$RNA$,and proteins) and their fragments based on their size and charge using a gel medium. It is an analytical tool,not a method for introducing foreign $DNA$ into host cells. In contrast,microinjection,heat shock,and gene gun (biolistics) are established methods for the transformation of host cells with recombinant $DNA$.

(B) In the process of $DNA$ isolation,the final step involves the addition of chilled ethanol to the purified $DNA$ solution.
Chilled ethanol is used because $DNA$ is insoluble in ethanol.
When chilled ethanol is added,$DNA$ precipitates out as fine threads in the suspension.
This process is known as spooling,which allows for the collection of the purified $DNA$.

(C) $PCR$ stands for Polymerase Chain Reaction.
It is a technique used in molecular biology to amplify a single copy or a few copies of a segment of $DNA$ across several orders of magnitude,generating thousands to millions of copies of a particular $DNA$ sequence.
Therefore,$PCR$ is primarily used for the amplification of $DNA$.

(C) In the microinjection method,recombinant $DNA$ is directly injected into the nucleus of an animal cell using microneedles. This technique is commonly used for animal cells. In contrast,the gene gun or biolistic method involves bombarding cells with high-velocity microparticles of gold or tungsten coated with $DNA$.

(D) In a continuous culture system,the culture medium is added continuously from one side while the used medium containing cells is drained out from the other side.
This allows the cells to be maintained in their physiologically most active log/exponential phase,which is a significant advantage over shake flasks where cells eventually enter the stationary phase due to nutrient depletion and waste accumulation.
Additionally,continuous culture systems facilitate the integration of continuous upstream and downstream processes,and they allow for long-term operation without the need for frequent shutdowns for cleaning and re-inoculation.

(A) The $PCR$ $(Polymerase Chain Reaction)$ technique requires a thermostable $DNA$ polymerase enzyme to synthesize new $DNA$ strands.
$Taq$ Polymerase is isolated from the bacterium $Thermus$ $aquaticus$.
This enzyme is thermostable,meaning it can withstand the high temperatures (around $94-95^{\circ}C$) required for the denaturation step of $PCR$ without getting denatured itself.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for why $Taq$ Polymerase is used in $PCR$.

(A) $1$. Tomato cells have a cell wall made of cellulose,which must be broken down by cellulase to release the cellular contents.
$2$. Proteins associated with the genetic material must be removed using protease.
$3$. To isolate pure $RNA$,the $DNA$ present in the cell must be degraded. Deoxyribonuclease $(DNase)$ is an enzyme that specifically digests $DNA$ but does not affect $RNA$.
$4$. Therefore,treating the mixture with $DNase$ ensures that $DNA$ is removed,leaving $RNA$ intact for extraction.
$5$. Both the Assertion and the Reason are correct,and the Reason provides the correct explanation for why $DNase$ is used in the extraction process.

(B) In recombinant $DNA$ technology,a probe is allowed to hybridize to its complementary $DNA$ in a clone of cells.
This technique is often used to identify clones containing a specific gene sequence.
The cells are then detected by autoradiography.
The cells with mutated genes will not be observed on the photographic film because the probe will not be complementary to the mutated gene sequence.

(C) Gene amplification using primers can be done by polymerase chain reaction $(PCR)$.
In this reaction,multiple copies of the gene of interest are synthesized in vitro using two sets of primers and the enzyme $DNA$ polymerase.
Primers are small,chemically synthesized oligonucleotides that are complementary to the regions of $DNA$.

(D) The production of human proteins in bacteria is possible due to the universality of the genetic code.
This means that the same codons specify the same amino acids in almost all living organisms,from bacteria to humans.
Therefore,when a human gene is inserted into a bacterial plasmid,the bacterial machinery can successfully transcribe and translate the human $DNA$ sequence into the corresponding functional human protein.

(B) The Polymerase Chain Reaction $(PCR)$ is a laboratory technique used to amplify small segments of $DNA$.
It allows for the rapid production of millions to billions of copies of a specific $DNA$ sequence from a very small initial sample.
Since only a small amount of $DNA$ was extracted from the ancient skull,$PCR$ is the most effective method to generate sufficient quantities for genetic analysis.

(D) Molecular probes are labeled $DNA$ segments,$RNA$ segments,or antibodies.
They are used to detect specific sequences or pathogens by binding to their complementary structures.
In genetic engineering,probes are primarily used during the screening process to identify transformed cells or specific gene sequences among a library of clones.

(B) In the process of recombinant $DNA$ technology,the isolation of genetic material involves the removal of unwanted cellular components like proteins,$RNA$,and polysaccharides using specific enzymes.
Once the purified $DNA$ is obtained in the solution,it is precipitated by adding chilled ethanol.
This process results in the appearance of $DNA$ as a collection of fine threads in the suspension,which can be removed by spooling.

(B) In the process of gel electrophoresis,$DNA$ fragments are separated based on their size.
To visualize these $DNA$ fragments,the gel is stained with a fluorescent dye called ethidium bromide $(EtBr)$.
When this gel is exposed to ultraviolet $(UV)$ radiation,the $EtBr$ intercalates into the $DNA$ and fluoresces.
Consequently,the $DNA$ fragments appear as bright orange-colored bands under $UV$ light.

(C) The Polymerase Chain Reaction $(PCR)$ is a technique used to amplify a specific segment of $DNA$. It involves three main steps that are repeated in cycles:
$1$. Denaturation: The double-stranded $DNA$ is heated to a high temperature (usually around $94-95^{\circ}C$) to separate the two strands.
$2$. Annealing: The temperature is lowered (usually $50-65^{\circ}C$) to allow the primers to bind to the complementary sequences on the single-stranded $DNA$ templates.
$3$. Extension: The temperature is adjusted (usually $72^{\circ}C$) for the $Taq$ $DNA$ polymerase enzyme to synthesize the new $DNA$ strand by adding nucleotides to the primers.
Therefore,the correct sequence is Denaturation,Annealing,and Extension.

(B) $PCR$ (Polymerase Chain Reaction) is a technique used to amplify a specific segment of $DNA$ in vitro.
Its primary applications include:
$1$. $Gene$ $amplification$: Creating millions of copies of a specific $DNA$ sequence.
$2$. $Molecular$ $diagnosis$: Detecting pathogens (like viruses or bacteria) in patients even when their concentration is very low.
$3$. $Detection$ of $gene$ $mutations$: Identifying specific genetic variations or mutations associated with diseases.
$4$. $DNA$ $fingerprinting$ and $forensic$ $analysis$.
Purification of isolated proteins is a downstream processing technique, not an application of $PCR$.

(A) The plasmid $pBR322$ contains two antibiotic resistance genes: $amp^R$ (ampicillin resistance) and $tet^R$ (tetracycline resistance).
Insertion of a foreign $DNA$ fragment at the $PstI$ restriction site,which is located within the $amp^R$ gene,results in insertional inactivation of the $amp^R$ gene.
Due to this inactivation,the recombinant plasmid loses its ability to confer ampicillin resistance to the host $E. coli$ cell.
Therefore,the transformed cells will be sensitive to ampicillin but will be able to express the inserted gene for $\beta$-galactosidase.

(C) The $PCR$ (Polymerase Chain Reaction) process consists of three main steps: $1$. Denaturation,$2$. Annealing,and $3$. Extension.
In the first step,Denaturation,the double-stranded $DNA$ template is heated to a very high temperature (approximately $94-98^{\circ}C$) to separate the two strands by breaking the hydrogen bonds between the complementary base pairs.
If this high temperature is not maintained at the beginning,the $DNA$ strands will not separate,and the subsequent steps (Annealing and Extension) cannot occur.
Therefore,Denaturation is the first step that will be affected.

(N/A) Hepatitis $B$ and Bird flu $DNA$ vaccines are called Recombinant $DNA$ vaccines because they are produced using recombinant $DNA$ technology. These vaccines consist of a small circular $DNA$ molecule (plasmid) into which a specific gene segment from the pathogen (virus) has been inserted. When this plasmid is introduced into the host,the host cells express the specific protein encoded by the pathogen's gene,which triggers an immune response without causing the actual disease.

(B) In gel electrophoresis,$DNA$ fragments are separated based on their size through a sieving effect provided by the agarose gel.
To visualize the $DNA$,the gel is stained with ethidium bromide $(EtBr)$.
When the stained gel is exposed to $UV$ radiation,the $DNA$ fragments appear as bright orange-coloured bands.
Option $B$ is incorrect because chromogenic substrates are typically used in blue-white screening for recombinant colonies,not for visualizing $DNA$ bands in gel electrophoresis.
The extraction of $DNA$ bands from the agarose gel is indeed known as elution.

(B) The process of transferring $DNA$ fragments from an agarose gel to a synthetic membrane (such as nitrocellulose or nylon) is known as blotting (specifically Southern blotting).
$1$. Electrophoresis is used to separate $DNA$ fragments based on their size.
$2$. $PCR$ (Polymerase Chain Reaction) is used for the amplification of $DNA$ segments.
$3$. Restriction digestion is the process of cutting $DNA$ molecules into smaller fragments using restriction enzymes.
Therefore,the correct process described is blotting.

(B) Bioprocess engineering is the technique that involves the maintenance of sterile conditions in chemical engineering processes to enable the growth of only the desired microbe or eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics,vaccines,and enzymes.

(B) The creation of Genetically Modified Organisms ($GMO$s) involves recombinant $DNA$ technology,which includes:
$1$. Identification of $DNA$ with desirable genes.
$2$. Introduction of the identified $DNA$ into the host.
$3$. Maintenance of introduced $DNA$ in the host and transfer of the $DNA$ to its progeny.
Hybridization between two parents with desirable traits is a traditional plant breeding method,not a step in the creation of $GMO$s via genetic engineering.

(C) $DNA$ fragments are negatively charged molecules.
In the technique of agarose gel electrophoresis,$DNA$ fragments are separated based on their size through a sieving effect provided by the agarose gel matrix.
When an electric field is applied,the $DNA$ fragments move towards the anode (positive electrode).
The smaller fragments move faster and travel further through the gel compared to larger fragments.

(C) Ethidium bromide $(EtBr)$ is a fluorescent dye used to visualize $DNA$ fragments in agarose gel electrophoresis.
When the gel is exposed to $UV$ light,the $EtBr$ molecules that have intercalated into the $DNA$ double helix absorb the $UV$ radiation and emit light in the orange-red spectrum.
Therefore,the $DNA$ bands appear as bright orange-colored bands under $UV$ light.

(D) Elution is a technique used in gel electrophoresis to recover $DNA$ fragments from an agarose gel.
After the $DNA$ fragments are separated by electrophoresis and visualized (usually by staining with ethidium bromide and exposure to $UV$ light),the specific $DNA$ bands of interest are cut out from the agarose gel.
These gel pieces containing the $DNA$ are then processed to extract and purify the $DNA$ fragments,a process known as elution.

(A) In gel electrophoresis,$DNA$ fragments are separated based on their size. Undigested $DNA$ is a large,intact molecule that does not move far from the well because it is too large to pass through the pores of the agarose gel matrix efficiently. Looking at the gel image,the lane labeled $1$ shows a single,large band near the well,indicating that the $DNA$ was not cut by restriction enzymes. Lanes $2, 3,$ and $4$ show multiple smaller bands,indicating that the $DNA$ was digested into smaller fragments. Therefore,the undigested $DNA$ was loaded in well $1$.

(A) The plasmid $pBR322$ contains two antibiotic resistance genes: $amp^R$ (ampicillin resistance) and $tet^R$ (tetracycline resistance).
The restriction site for the enzyme $Cla\, I$ is located within the $tet^R$ gene.
When foreign $DNA$ is inserted at the $Cla\, I$ site,the $tet^R$ gene undergoes insertional inactivation,meaning it becomes non-functional.
Consequently,the bacteria containing this recombinant plasmid will lose their resistance to tetracycline.
However,the $amp^R$ gene remains intact and functional.
Therefore,the transformed bacteria will be able to grow on ampicillin-containing medium but will fail to grow on tetracycline-containing medium.

(C) The process of introducing recombinant $DNA$ into a host cell is known as transformation.
To facilitate the uptake of $DNA$ by the host cell (like $E. coli$),the cells are treated with a divalent cation such as calcium $(Ca^{2+})$.
This increases the efficiency with which $DNA$ enters the bacterium through pores in its cell wall.
Recombinant $DNA$ can then be forced into such cells by incubating the cells with recombinant $DNA$ on ice,followed by placing them briefly at $42^{\circ} C$ (heat shock),and then putting them back on ice.
This enables the bacteria to take up the recombinant $DNA$.

(B) Microinjection is a technique used to introduce foreign $DNA$ directly into the nucleus of an animal cell using a fine glass micropipette. This method is commonly used in animal cells because they lack a cell wall,making it easier to penetrate the cell membrane and nuclear envelope.

(A) In the process of recombinant $DNA$ technology,after the removal of other macromolecules like $RNA$,proteins,and lipids using specific enzymes,the purified $DNA$ is precipitated out by adding chilled ethanol. This process is known as spooling,where the $DNA$ appears as a collection of fine threads in the suspension.

(D) The Polymerase Chain Reaction $(PCR)$ consists of three main steps:
$1$. Denaturation $(P)$: The double-stranded $DNA$ is heated to a high temperature of about $95^{\circ}C$ to separate the strands.
$2$. Annealing $(Q)$: The temperature is lowered to about $40-60^{\circ}C$ (typically $50-65^{\circ}C$,here $56^{\circ}C$) to allow the primers to bind to the template $DNA$.
$3$. Extension $(R)$: The temperature is raised to $72^{\circ}C$ to allow the $Taq$ $DNA$ polymerase to synthesize the new $DNA$ strand.
Therefore,the correct sequence of temperatures is $95^{\circ}C$ for $P$,$56^{\circ}C$ for $Q$,and $72^{\circ}C$ for $R$.

(A) The $PCR$ (Polymerase Chain Reaction) technique consists of three main steps: denaturation,annealing,and extension.
In the denaturation step,the double-stranded $DNA$ is heated to a high temperature (approximately $94^{\circ}C - 96^{\circ}C$).
This high temperature breaks the hydrogen bonds between the complementary base pairs,causing the two strands of $DNA$ to separate.
Unlike in vivo replication,where helicase is used to unwind $DNA$,$PCR$ uses thermal denaturation to separate the strands.

(B) In a simple stirred-tank bioreactor (represented by $P$),the stirrer facilitates even mixing and oxygen availability throughout the bioreactor.
In a sparged stirred-tank bioreactor (represented by $Q$),sterile air bubbles are sparged from the bottom,which increases the oxygen transfer surface area.
Therefore,$P$ is a simple stirred-tank bioreactor and $Q$ is a sparged stirred-tank bioreactor.

(D) Downstream processing in recombinant $DNA$ technology refers to the processes that occur after the product is synthesized in the bioreactor.
It primarily includes the separation,purification,quality control,and preservation of the products.
The expression of the desired gene to produce the product is a part of 'upstream processing',which occurs within the bioreactor.
Therefore,option $D$ is the correct answer.

(C) When a protein-encoding gene is expressed in a heterologous host, the protein produced is referred to as a $Recombinant$ $protein$.
This is a fundamental principle of biotechnology where the gene of interest is inserted into a vector and then introduced into a host organism (like $E. coli$ or yeast) to produce the desired protein in large quantities.

(B) $PCR$ (Polymerase Chain Reaction) is a technique used to amplify a specific $DNA$ segment.
It requires two sets of small,chemically synthesized oligonucleotides that are complementary to the regions of the $DNA$ template.
These two primers are known as the forward primer and the reverse primer.
They bind to the $3'$ ends of the two strands of the denatured $DNA$,allowing the $DNA$ polymerase to extend the sequence.
Therefore,$2$ types of primers are required for the amplification process.

(C) The Polymerase Chain Reaction $(PCR)$ consists of three main steps performed in a cyclic manner:
$1$. Denaturation: The double-stranded $DNA$ is heated to a high temperature (approx. $94-98^{\circ}C$) to separate the strands.
$2$. Annealing: The temperature is lowered (approx. $50-65^{\circ}C$) to allow primers to bind to the complementary sequences on the single-stranded $DNA$ templates.
$3$. Extension: The temperature is adjusted (approx. $72^{\circ}C$) for the $DNA$ polymerase enzyme to synthesize the new $DNA$ strand by adding nucleotides.
Therefore,the correct sequence is Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension.

(A) $PCR$ stands for Polymerase Chain Reaction.
It is a laboratory technique used to amplify specific $DNA$ sequences.
Since this process occurs outside of a living organism (in a test tube or reaction vessel), it is classified as an $In vitro$ method.
Therefore, the correct option is $A$.

(B) The Polymerase Chain Reaction $(PCR)$ is a technique used to amplify a specific $DNA$ segment. The number of $DNA$ copies produced after $n$ cycles is given by the formula $2^n$.
Given that the number of cycles $n = 30$, the total number of copies produced is $2^{30}$.
$2^{10} = 1,024$ (approximately $10^3$).
$2^{30} = (2^{10})^3 \approx (10^3)^3 = 10^9$.
Therefore, $2^{30}$ is approximately $1$ billion copies.

(B) bioreactor is a vessel in which raw materials are biologically converted into specific products by microbes,plant and animal cells,or their enzymes.
In the context of biotechnology,the process of preparing the culture medium and inoculating it with the desired organism is known as upstream processing.
The bioreactor provides the optimal conditions (temperature,pH,substrate,salts,vitamins,oxygen) for the growth of the organism and the production of the desired product.
Therefore,the main production phase,which involves the growth of the organism and the synthesis of the product,occurs within the bioreactor,which is a part of the upstream processing.
Downstream processing refers to the separation and purification of the product after it has been synthesized in the bioreactor.

(B) $mRNA$ silencing is a method of cellular defense in all eukaryotic organisms. This method involves the silencing of a specific $mRNA$ due to a complementary $dsRNA$ molecule that binds to and prevents translation of the $mRNA$. This process is known as $RNA$ interference or $RNAi$.

(D) $PCR$ (Polymerase Chain Reaction) is a powerful molecular diagnostic technique used to amplify specific $DNA$ sequences.
$1$. It is used to detect $HIV$ in suspected $AIDS$ patients even when the viral load is very low.
$2$. It is used to detect mutations in genes in suspected cancer patients,which helps in early diagnosis.
$3$. It is widely used to identify genetic disorders by analyzing specific $DNA$ segments.
Therefore,all the given options are correct applications of $PCR$ in molecular diagnostics.

(D) The separation of $DNA$ fragments based on their size is achieved through a technique called $Gel$ $electrophoresis$.
In this process,$DNA$ fragments are separated by forcing them to move through a gel matrix (usually agarose) under an electric field.
Since $DNA$ molecules are negatively charged,they move towards the anode (positive electrode).
The smaller fragments move faster and travel further through the pores of the gel compared to larger fragments,allowing for effective separation.