Mix Examples - Biotechnology Principals and Process Questions in English

(A) Agrobacterium tumefaciens (updated scientific name: Rhizobium radiobacter) is the causal agent of crown gall disease (the formation of tumours) in over $140$ species of dicots. It is a rod-shaped,Gram-negative soil bacterium.
Symptoms are caused by the insertion of a small segment of $DNA$,known as $T-DNA$ (transfer $DNA$),into the plant cell,which is incorporated at a semi-random location into the plant genome.
Option $A$ is correct because Agrobacterium tumefaciens naturally transfers $T-DNA$ into plant cells,causing crown gall tumours.
Option $B$ is incorrect because Thermus aquaticus is the source of Taq polymerase,not the Bt-gene.
Option $C$ is incorrect because $pBR322$ is a cloning vector (plasmid),not an enzyme.
Option $D$ is incorrect because restriction endonucleases are known as molecular scissors,while ligase is known as molecular glue.

(D) $PCR$ (Polymerase Chain Reaction) can detect very low amounts of $DNA$ by amplifying the target sequence.
$PCR$ is routinely used to detect $HIV$ in suspected $AIDS$ patients.
It is also used to detect mutations in genes in suspected cancer patients.
Furthermore,it is a powerful technique used to identify and diagnose many other genetic disorders.

(A) Assertion $(A)$ is correct because the Polymerase Chain Reaction $(PCR)$ is a technique used to amplify a specific segment of $DNA$ in vitro.
Reason $(R)$ is also correct because the ampicillin resistance gene is a well-known selectable marker used in cloning vectors to identify transformed cells from non-transformed ones.
However,the reason $(R)$ does not explain why $PCR$ is used for $DNA$ amplification. Both statements are scientifically accurate,but they describe two different aspects of biotechnology.
Therefore,both $(A)$ and $(R)$ are correct,but $(R)$ is not the correct explanation of $(A)$.

(A) The first artificial recombinant $DNA$ was constructed by Stanley Cohen and Herbert Boyer in $1972$.
They isolated an antibiotic resistance gene from the plasmid of the bacterium $Salmonella\,typhimurium$.
This gene was then linked to a native plasmid of $Escherichia\,coli$ using the enzyme $DNA$ ligase.
Therefore, the correct combination is the plasmid and the antibiotic resistance gene.

(B) In recombinant $DNA$ technology,$X-gal$ ($5$-bromo$-4-$chloro$-3-$indolyl-$\beta$-$D$-galactopyranoside) is a chromogenic substrate used to detect the activity of the enzyme $\beta$-galactosidase.
When the enzyme $\beta$-galactosidase is present and active,it cleaves the $X-gal$ molecule.
This cleavage results in the formation of an insoluble blue-colored product.
This process is commonly used in blue-white screening to identify recombinant colonies in cloning experiments.

(C) The incorrect option is $C$. $\text{Taq}$ polymerase is a heat-stable $\text{DNA}$ polymerase,not an $\text{RNA}$ polymerase. It is isolated from the bacterium $\text{Thermus aquaticus}$.
Elution is the process of extracting $\text{DNA}$ fragments from the agarose gel.
Spooling is the process of removing precipitated $\text{DNA}$ from a solution using a glass rod.
$\text{PCR}$ (Polymerase Chain Reaction) is a technique that involves thermal cycling to amplify $\text{DNA}$ segments.

(B) The Assertion is correct: The $Ti$ plasmid of $Agrobacterium$ $tumefaciens$ is a natural genetic engineer that transfers $DNA$ into plants. Scientists have modified it into a cloning vector by removing the tumor-inducing genes,making it safe for gene transfer.
The Reason is also correct: Retroviruses have the ability to infect cells and integrate their genetic material into the host genome. By disarming them (removing pathogenic genes),they are successfully used as vectors to deliver desired genes into animal cells.
Both statements are factually correct,but the Reason does not explain why the $Ti$ plasmid was modified; it describes a separate mechanism for animal cell transformation. Therefore,the Reason is not the correct explanation of the Assertion.

(B) The correct matches are as follows:
$1$. $\text{YAC}$ (Yeast Artificial Chromosome) is a vector used in $\text{Yeast}$. Thus,$(A)$ matches with $(II)$.
$2$. $\text{Hind II}$ was the first restriction endonuclease discovered. Thus,$(B)$ matches with $(III)$.
$3$. Gel electrophoresis is a technique used for the separation of $\text{DNA}$ fragments based on their size. Thus,$(C)$ matches with $(I)$.
$4$. $A$ heterologous host is used for the expression of the gene of interest to produce a recombinant protein. Thus,$(D)$ matches with $(IV)$.
Therefore,the correct sequence is $A-II, B-III, C-I, D-IV$.

(B) Statement $(I)$ is correct: Disarmed $Agrobacterium$ $tumefaciens$ is widely used as a vector to transfer foreign genes into plant cells.
Statement $(II)$ is incorrect: In $\text{EcoRI}$,the letter '$R$' is derived from the name of the strain (e.g.,$RY13$),not the species.
Statement $(III)$ is correct: Gene therapy is a significant application of modern biotechnology used to treat genetic disorders.
Statement $(IV)$ is incorrect: $\text{DNA}$ is a hydrophilic (water-loving) molecule and cannot pass through cell membranes easily because cell membranes are composed of a hydrophobic lipid bilayer. Special techniques like microinjection or electroporation are required.
Since statements $(II)$ and $(IV)$ are incorrect,the correct option is $B$.

(C) Statement $(A)$ is correct: Hind $II$ was the first restriction endonuclease isolated from the bacterium Haemophilus influenzae.
Statement $(B)$ is correct: When a protein-encoding gene is expressed in a heterologous host,the protein produced is referred to as a recombinant protein.
Statement $(C)$ is correct: Microinjection is a direct method of gene transfer used specifically for animal cells,where foreign $DNA$ is injected directly into the nucleus.
Statement $(D)$ is correct: In $\text{PCR}$,primers are small,chemically synthesized oligonucleotides that are complementary to the regions of the template $\text{DNA}$.
Since all four statements $(A, B, C, D)$ are correct,the total number of correct statements is $4$.

(C) . Bioreactors are vessels in which raw materials are biologically converted into specific products using microbial,plant,or animal cells.
$B$. Downstream processing refers to the processes of separation and purification of the product after the biosynthetic stage.
$C$. Recombinant protein refers to the protein encoded by the recombinant $DNA$,such as insulin produced by rDNA technology.
$D$. $PCR$ (Polymerase Chain Reaction) is a technique used to amplify $DNA$ segments and can be used to detect mutated genes in suspected cancer patients.
Therefore,the correct match is $A-ii, B-iv, C-i, D-iii$.

(A) . Genetically modified organism: Bt cotton $(II)$
$B$. $DNA$ polymerase: Thermus aquaticus $(III)$
$C$. Ti plasmid: Agrobacterium tumefaciens $(I)$
$D$. pBR322: Escherichia coli $(IV)$
Therefore,the correct matching is $A-II, B-III, C-I, D-IV$.