NEET Biotechnology and Its Applications: Important Questions and Answers by PW

Biotechnology questions test your understanding of genetic engineering, recombinant DNA technology and the use of biological systems in medicine and agriculture. You need to remember the functions of enzymes and vectors, understand experimental steps, and connect important examples with their applications.

Physics Wallah supports your NEET Biology preparation with concept revision and question practice. Use these important questions to revise key principles, clarify common confusions and strengthen your understanding of Biotechnology and Its Applications.

Biotechnology and Its Applications: Important Questions

Question 1: What Are the Two Core Techniques of Modern Biotechnology?

Answer: The two core techniques of modern biotechnology are genetic engineering and bioprocess engineering.

• Genetic engineering: Involves the deliberate modification of genetic material to introduce or alter specific characteristics.

• Bioprocess engineering: Involves maintaining suitable conditions for growing cells or microorganisms and producing useful biological products on a large scale.

These techniques are used in healthcare, agriculture, industrial production and the development of genetically modified organisms.

Question 2: In Which Direction Does DNA Move During Agarose Gel Electrophoresis?

Answer: DNA moves from the negative electrode, or cathode, towards the positive electrode, or anode.

DNA has a negatively charged phosphate backbone, which causes it to move towards the positive electrode in an electric field.

During agarose gel electrophoresis:

• DNA samples are loaded into wells near the cathode.

• Smaller DNA fragments move faster through the gel and travel farther.

• Larger DNA fragments migrate more slowly and remain closer to the loading wells.

DNA bands can be visualised by staining the DNA with ethidium bromide and observing it under ultraviolet radiation.

Remember: DNA moves towards the anode, and smaller fragments travel farther.

Question 3: What Is the Difference Between Digested and Undigested DNA?

Answer: Digested DNA has been treated with restriction enzymes, whereas undigested DNA has not undergone restriction enzyme cleavage.

Restriction enzymes cut DNA at specific recognition sequences. Depending on the DNA molecule and the enzyme used, digestion produces fragments of different sizes that can be separated through gel electrophoresis.

Undigested DNA generally produces a different migration pattern because it remains uncut. Its migration also depends on the molecule's size and shape.

Question 4: What Is PCR, and How Does It Amplify DNA?

Answer: Polymerase chain reaction (PCR) is a technique used to amplify a selected DNA segment, producing millions or billions of copies under suitable conditions.

During ideal amplification, the DNA quantity approximately doubles with each cycle.

The theoretical relationship is:

N = 2ⁿ 

Here, (N) represents the number of DNA copies from one starting double-stranded DNA molecule after (n) ideal cycles.

For example:

• After 1 cycle: 2 copies

• After 2 cycles: 4 copies

• After 3 cycles: 8 copies

• After 4 cycles: 16 copies

Kary Mullis is associated with the development of PCR.

Remember: PCR amplifies DNA through repeated cycles of denaturation, annealing and extension.

Question 5: What Are the Three Steps of PCR?

Answer: The three main steps of PCR are denaturation, annealing and extension.

1. Denaturation: Heating separates double-stranded DNA into two single strands.

2. Annealing: Primers bind to their complementary sequences on the DNA strands.

3. Extension: Taq DNA polymerase extends the primers by adding nucleotides to synthesise new DNA strands.

Taq polymerase is required for DNA synthesis during extension, not for primer annealing.

Question 6: What Is the Function of Taq DNA Polymerase in PCR?

Answer: Taq DNA polymerase synthesises new DNA strands by extending primers during PCR.

It is obtained from the thermophilic bacterium Thermus aquaticus. Its thermostability allows it to function during repeated PCR heating cycles without requiring replacement after every denaturation step.

Question 7: What Is the Recognition Sequence of EcoRI, and How Does It Produce Sticky Ends?

Answer: EcoRI recognises the palindromic DNA sequence GAATTC and cuts the DNA strands in a staggered manner, producing sticky ends.

The recognition sequence is:

5′-GAATTC-3′ 3′-CTTAAG-5′ 

The staggered cuts produce complementary single-stranded overhangs. These sticky ends can pair with complementary ends of another DNA fragment.

DNA ligase then seals the sugar-phosphate backbone to form recombinant DNA.

Restriction endonucleases break phosphodiester bonds in DNA, not glycosidic bonds.

Question 8: How Is Recombinant DNA Formed Using Restriction Enzymes?

Answer: Recombinant DNA is formed by joining DNA fragments from different sources.

The process involves the following steps:

1. Identify the desired gene and the vector.

2. Cut the foreign DNA and vector using the same suitable restriction enzyme.

3. Allow complementary sticky ends to pair.

4. Use DNA ligase to join the fragments.

5. Obtain the recombinant DNA molecule.

Restriction enzymes cut DNA at specific sequences, while DNA ligase joins the DNA fragments by sealing the backbone.

Question 9: What Is a Plasmid, and Why Is It Used as a Cloning Vector?

Answer: A plasmid is generally a circular, double-stranded, extrachromosomal DNA molecule that can replicate independently inside a bacterial cell.

Plasmids are used as cloning vectors because they can carry foreign DNA into host cells and allow its replication or maintenance.

A useful cloning vector generally contains:

• An origin of replication.

• A selectable marker.

• Suitable restriction sites.

• Features that allow the inserted DNA to be maintained in the host.

Other vectors used in genetic engineering include bacteriophages, cosmids, phagemids and shuttle vectors.

A bacterium is the host organism, not the vector itself.

Question 10: What Are the Important Components of the pBR322 Vector?

Answer: pBR322 is a commonly studied plasmid cloning vector used in genetic engineering.

Its important components include:

• Ampicillin-resistance gene: Acts as a selectable marker.

• Tetracycline-resistance gene: Acts as another selectable marker.

• ori: The origin of replication, where DNA replication begins.

• rop gene: Encodes a protein involved in regulating plasmid replication and copy number.

• Restriction sites: Include sites recognised by enzymes such as EcoRI, HindIII, PstI and PvuII.

The location of the inserted foreign DNA determines whether a selectable marker is disrupted.

Question 11: What Happens When Foreign DNA Is Inserted at the EcoRI Site of pBR322?

Answer: When foreign DNA is inserted at the EcoRI site of pBR322, neither the ampicillin-resistance gene nor the tetracycline-resistance gene is disrupted.

Therefore, the resulting transformants can retain resistance to both ampicillin and tetracycline.

The antibiotic-resistance pattern depends on the insertion site. If foreign DNA disrupts one of the resistance genes, that gene may no longer function, helping distinguish recombinant bacteria from non-recombinant bacteria.

Question 12: How Does Blue–White Screening Work in the pUC Vector?

Answer: Blue–white screening distinguishes recombinant and non-recombinant colonies by examining whether the lacZ gene remains functional.

The pUC vector contains a lacZ region and an ampicillin-resistance marker.

• Blue colonies: lacZ remains functional, allowing beta-galactosidase activity under the screening conditions. These colonies are generally non-recombinant.

• White colonies: Insertion of foreign DNA disrupts lacZ, preventing the expected colour reaction. These colonies are generally recombinant.

Ampicillin resistance selects transformants, while colony colour helps distinguish recombinant colonies.

Memory tip: Blue means functional lacZ; white means disrupted lacZ.

Question 13: What Are the Major Steps of Recombinant DNA Technology?

Answer: Recombinant DNA technology involves isolating, modifying and introducing DNA into a suitable host.

The major steps are:

1. Isolation of DNA.

2. Cutting DNA with restriction enzymes.

3. Isolation of the desired DNA fragment.

4. Amplification of the fragment, when required.

5. Ligation of the fragment into a suitable vector.

6. Introduction of recombinant DNA into a host cell.

7. Selection of suitable host cells.

8. Replication and maintenance of the recombinant DNA.

The introduction of recombinant DNA into a bacterial host cell is called transformation. Gene cloning involves producing multiple copies of the desired DNA fragment.

Question 14: Which Enzymes Are Used to Isolate DNA from Fungal and Bacterial Cells?

Answer: Different enzymes are used to break down cellular components and remove unwanted material during DNA isolation.

• Chitinase: Breaks down the chitin-containing cell wall of fungi.

• Lysozyme: Helps break down bacterial cell walls.

• RNase: Removes RNA.

• Protease: Removes proteins.

• DNase: Degrades DNA and is therefore avoided when intact DNA is required.

The enzyme used depends on the organism and the cellular component that must be removed.

Question 15: What Is the Difference Between Exonuclease and Endonuclease?

Answer: Exonucleases remove nucleotides from the ends of DNA or RNA molecules, whereas endonucleases cleave bonds within a nucleic acid strand.

Restriction endonucleases recognise particular DNA sequences and cut DNA at defined positions.

Memory tip: Exonucleases act at the ends; endonucleases cut within the strand.

Question 16: What Is the Role of Methylase in the Restriction–Modification System?

Answer: Methylase modifies specific DNA sequences through methylation, helping protect the host's own DNA from cleavage by its restriction enzymes.

Restriction endonucleases recognise and cut particular DNA sequences, while the corresponding methylases help distinguish protected host DNA from susceptible DNA.

Together, these enzymes form a restriction–modification system.

Question 17: What Is the Correct Sequence of Heat-Shock Transformation?

Answer: The commonly taught sequence is:

Ice → Heat shock → Ice

Competent bacterial cells are often treated with calcium chloride before heat shock. Calcium ions help facilitate the interaction between DNA and the bacterial cell surface, increasing the likelihood of DNA uptake.

After heat shock, the cells are allowed to recover under suitable conditions.

Question 18: What Is a Bioreactor, and What Are Its Major Components?

Answer: A bioreactor is a vessel that provides controlled conditions for growing cells or microorganisms and producing useful biological products on a large scale.

The stirred-tank bioreactor is a commonly used design.

Its important components and systems include:

• Agitation or stirring system.

• Oxygen-delivery system.

• Temperature and pH controls.

• Foam-control system.

• Nutrient supply.

• Sterile operating conditions.

• Sampling port.

The sampling port allows small amounts of culture to be withdrawn for monitoring growth, contamination and product formation.

A flat-blade impeller helps mix the culture, while a foam breaker controls excessive foam. Steam may be used for sterilisation.

Question 19: What Is Downstream Processing in Biotechnology?

Answer: Downstream processing involves recovering and purifying a biological product after its production in a bioreactor.

It can include:

1. Separation of the product from cells or culture medium.

2. Purification of the desired product.

3. Formulation into a suitable final preparation.

4. Quality-control testing.

Downstream processing is distinct from the growth conditions maintained inside a bioreactor.

Question 20: Why Is the C-Peptide Absent in Mature Insulin?

Answer: The C-peptide is removed during the conversion of proinsulin into mature insulin.

Mature human insulin contains two polypeptide chains:

• A chain.

• B chain.

The chains are connected by disulfide linkages. The C-peptide is present in proinsulin but is absent from mature insulin after processing.

Memory tip: Mature insulin consists of A and B chains; the C-peptide is removed.

Question 21: How Was Recombinant Human Insulin Produced Using Bacteria?

Answer: Eli Lilly developed genetically engineered human insulin using Escherichia coli.

The A and B chains of human insulin were produced separately in bacterial cells and then combined to form functional insulin.

This approach helped produce human insulin using recombinant DNA technology rather than relying solely on insulin extracted from animal sources.

Question 22: Why Is Insulin Not Routinely Administered Orally?

Answer: Insulin is a protein hormone that can be broken down by digestive enzymes in the gastrointestinal tract.

Oral administration does not reliably deliver intact insulin into the bloodstream in the required amount. Therefore, conventional insulin treatment generally uses injection, although specialised delivery approaches continue to be studied and developed.

Question 23: What Is Gene Therapy? Explain Its Application in ADA Deficiency.

Answer: Gene therapy introduces genetic material into cells to compensate for or address the effects of a defective gene.

In adenosine deaminase (ADA) deficiency, a functional ADA gene can be introduced into suitable cells.

The approach described in the NCERT context involves:

1. Collecting lymphocytes from the affected individual.

2. Introducing functional ADA cDNA using a suitable vector, such as a retroviral vector.

3. Growing the genetically modified lymphocytes.

4. Infusing the modified cells back into the individual.

Repeated infusions may be necessary because lymphocytes are not immortal and eventually die.

Introducing a functional gene into suitable cells at an early embryonic stage may provide a more lasting correction, depending on the cells modified and the treatment approach.

Question 24: Which Molecular Techniques Are Used for Disease Diagnosis?

Answer: Important molecular diagnostic techniques include PCR, recombinant DNA technology, ELISA, DNA probe hybridisation and autoradiography.

• PCR: Amplifies selected DNA sequences so they can be detected more easily.

• ELISA: Detects specific antigens or antibodies through antigen–antibody interactions.

• DNA probe hybridisation: Identifies complementary nucleic acid sequences using a labelled probe.

• Autoradiography: Detects radioactive labels associated with DNA fragments or other biological material.

• Recombinant DNA technology: Supports the analysis and manipulation of genetic material.

These techniques are useful in detecting infections, genetic changes and disease-associated molecules.

Question 25: What Is the Principle of ELISA?

Answer: ELISA, or enzyme-linked immunosorbent assay, is based on antigen–antibody interactions.

An enzyme-linked detection system produces a measurable signal when the target interaction occurs. This often produces a colour change.

Commonly used enzymes include peroxidase and alkaline phosphatase.

The result depends on the design of the assay and the presence of the target antigen or antibody.

Biotechnology and Its Applications becomes easier to revise when you connect each technique with its principle, process and practical application. Focus on restriction enzymes, cloning vectors, PCR, recombinant insulin, gene therapy, molecular diagnosis, Bt crops, RNA interference and transgenic animals. Physics Wallah supports your NEET  Biology preparation with concept revision and question practice.

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