Biotechnology

The orchid Ophrys ensures pollination by mimicking the appearance and scent of a female bee. Male bees, attracted to the orchid, attempt to mate with it (pseudocopulation) and inadvertently carry pollen to other flowers.

Transgenic animals are those that have had foreign genes deliberately inserted into their genome. These genes are introduced to study gene functions, improve livestock traits, or produce biologically important substances.

Structure of Sparged Stirred-Tank Bioreactor:

A sparged stirred-tank bioreactor is a commonly used vessel for carrying out fermentation and large-scale cultivation of microorganisms or cells. The key components of its structure include:

• Cylindrical Vessel: The main body is a vertical cylindrical tank made of stainless steel, often jacketed for temperature control.
• Agitator (Impeller): A motor-driven shaft with blades inside the tank helps in mixing the contents to ensure uniform distribution of nutrients and cells.
• Sparger: A gas-inlet device at the bottom of the tank that introduces sterile air or gases (like oxygen) in the form of fine bubbles into the culture medium.
• Baffles: Vertical plates attached to the inner walls to reduce vortex formation and improve mixing efficiency.
• Ports and Sensors: Multiple ports for inoculation, sampling, pH and temperature sensors, nutrient addition, and harvesting.
• Control System: Automated controls for parameters like pH, temperature, aeration rate, and agitation speed.

Working of Sparged Stirred-Tank Bioreactor:

The working of the bioreactor involves the following steps:

1. Sterilization: The bioreactor is first sterilized to prevent contamination.
2. Inoculation: The desired microbial culture or cells are introduced into the sterile nutrient medium.
3. Agitation: The impeller continuously stirs the medium to keep the cells in suspension, distribute nutrients evenly, and improve heat and mass transfer.
4. Aeration: The sparger injects air or oxygen into the culture. The bubbles rise and dissolve in the liquid, providing the oxygen needed for aerobic metabolism.
5. Monitoring and Control: pH, temperature, and dissolved oxygen are constantly monitored and controlled using feedback systems to maintain optimal growth conditions.
6. Product Harvesting: After sufficient biomass or product accumulation, the contents are harvested for downstream processing.

Advantages:

• Efficient oxygen transfer due to sparging and stirring
• Uniform mixing ensures consistent environmental conditions for cells
• Scalable and suitable for industrial production of biomolecules

Conclusion:

The sparged stirred-tank bioreactor is an essential tool in biotechnology and industrial microbiology for culturing cells under controlled conditions, especially for the production of pharmaceuticals, enzymes, and other biologically important products.

Step 1 (a): The palindromic sequence of 5' – GAATTC – 3' is:
5' – GAATTC – 3'
3' – CTTAAG – 5'
It reads the same in 5' to 3' direction on both strands, making it a palindrome.

Step 2 (b): The restriction endonuclease that recognizes this sequence is EcoRI.

Step 3 (c): EcoRI cuts between G and A in both strands as follows:
5' – G↓AATTC – 3'
3' – CTTAA↑G – 5'
This creates **sticky ends** (overhanging single-stranded regions) which can form hydrogen bonds with complementary sequences.

Step 4: Sticky ends facilitate the insertion of foreign DNA during genetic engineering by allowing ligation with complementary sequences.

1. Transgenic animals are those animals whose DNA has been altered by introducing a foreign gene from another organism. They carry and express an extra (trans) gene.

1. Vaccine Safety: Transgenic mice are used to test the safety of vaccines before they are used on humans. Example: Polio vaccine trials.
2. Biological Products: Transgenic animals are engineered to produce useful biological substances like proteins. Example: Transgenic sheep producing human alpha-1-antitrypsin to treat emphysema.

[(i)] The protein produced by Bacillus thuringiensis is in inactive form (protoxin) inside the bacteria. It becomes active only in the alkaline gut of insects.
[(ii)] The gene coding for this protein has been incorporated into cotton plants. This makes Bt cotton produce the insecticidal protein, which kills bollworm pests on consumption.
[(i)] In the diagram of pBR322 vector:

‘a’ is amp gene (ampicillin resistance)

‘b’ is tet gene (tetracycline resistance)

[(ii)] The -galactosidase gene produces a visible colour change when active. This allows for blue-white screening, a simpler and faster method to identify recombinant colonies.
[(iii)] Uses of Cloning Vector:

For producing multiple copies of a specific gene.
For transferring desirable genes into host organisms.

(A):
Step 1: For (i), a bacterial cell is made ‘competent’ to take up recombinant DNA by treating it with calcium chloride (CaCl ) and subjecting it to a heat shock. The CaCl makes the cell membrane permeable by interacting with the negative charges on the membrane, and the heat shock (42°C for a brief period) creates a temperature gradient that allows the DNA to enter the cell through transient pores.
Step 2: For (ii), PCR (Polymerase Chain Reaction) amplifies a gene of interest in three steps per cycle: (1) Denaturation at 94–95°C to separate the DNA strands, (2) Annealing at 50–60°C to allow primers to bind to the target DNA, and (3) Extension at 72°C where Taq polymerase adds nucleotides to synthesize new DNA strands. This cycle repeats 25–30 times to exponentially amplify the gene.
OR
(B):
Step 3: For (i), transgenic animals are organisms that have had a foreign gene (transgene) inserted into their genome using genetic engineering techniques, resulting in the expression of a new trait.
Step 4: For (ii), transgenic animals are produced for four reasons: (1) To study gene function and regulation in a living organism, (2) To produce pharmaceuticals, like human proteins (e.g., insulin) in their milk, (3) To improve agricultural traits, such as disease resistance or growth rates in livestock, and (4) To model human diseases for research, like creating mice models for cancer studies.
Thus, (A) explains bacterial competence and PCR steps, while (B) defines transgenic animals and provides reasons for their production.

Gel electrophoresis is a widely used technique to separate DNA fragments based on size. The process involves the following steps:

1. A gel matrix (usually agarose) is prepared and submerged in an electrophoresis chamber. DNA samples are loaded into wells at one end of the gel.
2. An electric current is applied across the gel, and DNA, which is negatively charged, moves towards the positive electrode.
3. The gel acts as a sieve, allowing smaller DNA fragments to move faster through the matrix than larger ones, thus separating them based on size.
4. After electrophoresis is completed, the DNA fragments are stained with a dye (like ethidium bromide), and the gel is exposed to UV light, allowing visualization of the separated fragments as bands.

This method helps in analyzing DNA for various purposes, such as DNA profiling, gene cloning, or identifying mutations.

(i) The full form of ELISA is Enzyme-Linked Immunosorbent Assay. It is a diagnostic tool used for detecting the presence of an antigen or antibody in a sample. The test is based on the principle of antigen-antibody interaction. In this method, an antigen is immobilized on a solid surface, and an antibody, which is linked to an enzyme, binds to the antigen. The enzyme is then used to catalyze a reaction with a substrate, generating a color change or signal that can be quantified. This principle allows for high sensitivity and specificity in detecting trace amounts of substances.

(ii) Adenosine deaminase (ADA) deficiency leads to Severe Combined Immunodeficiency (SCID). The treatments include:

1. Enzyme Replacement Therapy (ERT): Administration of PEG-ADA (pegylated ADA), a modified enzyme that compensates for the missing ADA enzyme. This method helps partially restore immune system functions.
   
2. Bone Marrow Transplantation (BMT): The most common curative method. In this procedure, healthy bone marrow from a matched donor is transplanted into the patient to restore normal ADA function. It is especially effective in younger patients with a matched donor.
   
3. Gene Therapy: A revolutionary method where the patient's own stem cells are modified outside the body to include a functional copy of the ADA gene. These modified cells are then reintroduced to the patient to produce the necessary enzyme.

(A) Step 1: Bacterial cells are lysed using enzymes such as lysozyme to break the cell wall.
Step 2: Detergents like SDS (sodium dodecyl sulfate) are used to break open cell membranes and release cellular contents.
Step 3: Proteins and RNA are removed by treatment with protease and RNase enzymes respectively.
Step 4: The purified DNA is then precipitated by adding chilled ethanol or isopropanol.
OR
(B) Step 1: DNA sequences encoding the insulin A and B chains were isolated and inserted into plasmids.
Step 2: These recombinant plasmids were introduced into E. coli bacteria.
Step 3: The bacteria produced the A and B chains separately.
Step 4: These chains were extracted and chemically joined to form functional human insulin.

(A) Step 1: The technique involves the use of Bt cotton, a genetically modified crop.
Step 2: It contains genes from Bacillus thuringiensis that produce Cry proteins.
Step 3: When ingested by insect larvae, Cry proteins form pores in their midgut epithelium, causing cell lysis and death.
Conclusion: This makes the cotton plant pest-resistant and reduces pesticide use.
OR
(B) Two molecular diagnostic techniques:

• PCR (Polymerase Chain Reaction): Detects the presence of pathogen DNA by amplifying it from minute quantities.
• ELISA (Enzyme-Linked Immunosorbent Assay): Detects antigens or antibodies using antigen-antibody interaction and enzyme-linked indicators.

Transgenic animals are those that have had a foreign gene deliberately inserted into their genome. They are produced for a variety of scientific, medical, and industrial reasons. Here are four major reasons:

1. To study gene functions and regulation

Transgenic animals help scientists understand how specific genes work.

By adding or removing genes, researchers can study their role in development, immunity, diseases, and metabolism.

For example, knockout mice are used to investigate the function of individual genes.

2. To model human diseases

They are used to mimic human genetic disorders, helping researchers study the disease progression and test potential treatments.

Diseases like cystic fibrosis, cancer, Alzheimer’s, and diabetes have been studied using transgenic mice.

3. For production of therapeutic proteins

Transgenic animals can be engineered to produce human proteins in their milk, eggs, or blood (a process called “gene pharming”).

Example: Transgenic goats producing antithrombin, a protein used to prevent blood clots in humans.

4. To improve livestock quality

Genes can be inserted to improve traits such as growth rate, disease resistance, milk production, or meat quality.

This helps in creating more productive and disease-resistant animals, enhancing agricultural efficiency.

The correct answer is ELISA

Understanding Techniques for Early Disease Detection

The question asks which technique is used for the early detection of a disease based on the principle of antigen-antibody interaction. Antigen-antibody interactions are central to immunological diagnostic methods, where specific antibodies bind to target antigens to identify the presence of a disease.

Identifying the Correct Technique

Among the listed options, ELISA (Enzyme-Linked Immunosorbent Assay) is the technique that relies on antigen-antibody interactions for detecting diseases. It is widely used for early diagnosis of various conditions, such as infections and autoimmune disorders.

• ELISA: Enzyme-Linked Immunosorbent Assay is a diagnostic tool that detects antigens (e.g., pathogen proteins) or antibodies in a sample by using specific antigen-antibody binding. An enzyme-linked reaction produces a measurable signal, typically a color change, to indicate the presence of the target. ELISA is used for diseases like HIV, hepatitis, and COVID-19 due to its sensitivity and specificity.
• RNAi: RNA interference is a biological process where RNA molecules inhibit gene expression, typically used in research to silence specific genes. It is not a diagnostic technique and does not involve antigen-antibody interactions.
• EST: Expressed Sequence Tag is a short sequence of DNA derived from cDNA, used in genomics to identify gene transcripts. It is a tool for gene discovery, not a diagnostic method or related to antigen-antibody interactions.
• PCR: Polymerase Chain Reaction amplifies DNA segments for detection of genetic material, such as pathogen DNA or RNA. While PCR is used for disease diagnosis (e.g., detecting SARS-CoV-2), it targets nucleic acids, not antigen-antibody interactions.

Based on the principle of antigen-antibody interaction, ELISA is the correct technique for early disease detection.

Comparing Diagnostic Techniques

Here is a comparison of the techniques mentioned in the options:

Therefore, ELISA is the technique for early disease detection based on antigen-antibody interactions.

Revision Table: Key Techniques in Molecular Biology and Diagnostics

Additional Information on ELISA and Antigen-Antibody Interactions

ELISA, developed in the 1970s, revolutionized medical diagnostics by leveraging the specificity of antigen-antibody interactions. The technique involves immobilizing an antigen or antibody on a solid surface, adding a sample, and using enzyme-linked antibodies to produce a detectable signal. Variants like sandwich, direct, and indirect ELISA allow flexibility in detecting different targets. Its applications extend beyond infectious diseases to include hormone levels, allergies, and cancer markers. The Mahabharata period, while unrelated to modern diagnostics, reflects early Indian knowledge of health and medicine, as seen in references to healing practices in the epic. ELISA’s role in modern medicine underscores the importance of immunological techniques in early disease detection, ensuring timely intervention and improved health outcomes.

Transgenic animals are those animals whose DNA has been deliberately altered by introducing a foreign gene. These animals carry and express an extra gene (transgene) from another organism. Four important uses of transgenic animals for human benefit:

(B) Normal physiology and development: To study gene regulation and the effect of genes on normal functions and development.
(C) Disease models: To understand the development and progression of diseases like cancer, cystic fibrosis, rheumatoid arthritis, etc.
(D) Biological products: Transgenic animals can be used to produce therapeutic proteins such as human insulin or α-1-antitrypsin in their milk.
(E) Vaccine safety testing: Transgenic mice are used for toxicity and safety tests for vaccines.

Step 1: (a) The enzyme used to make multiple copies of foreign DNA is DNA polymerase, specifically Taq polymerase during the PCR (Polymerase Chain Reaction) process.
Step 2: (b) EcoR I creates sticky ends (overhanging sequences) in both plasmid and foreign DNA.

• These sticky ends are complementary, allowing the foreign DNA to bind with the plasmid DNA.
• DNA ligase then joins the sugar-phosphate backbones, forming a stable recombinant DNA molecule.

Step 3: (c) The most commonly used host is Escherichia coli (E. coli).

Polymerase Chain Reaction (PCR) is a technique used to amplify a gene or DNA segment of interest.
Steps of PCR:

1. Denaturation: The double-stranded DNA is heated to to separate it into two single strands.
2. Annealing: The temperature is lowered to to allow primers to bind (anneal) to the complementary sequences on the single-stranded DNA.
3. Extension: The temperature is raised to around , and Taq DNA polymerase adds nucleotides to the primers, extending the DNA and synthesizing new strands.

Cycle Repetition: These steps are repeated for 25–35 cycles, exponentially increasing the quantity of the target DNA.

The biotechnological strategy used is called RNA interference (RNAi).

Explanation:

• RNA interference is a method of gene silencing where double-stranded RNA (dsRNA) prevents the expression of specific genes.
  
• In this technique, genes encoding dsRNA specific to the nematode’s essential genes are introduced into the tobacco plant using Agrobacterium tumefaciens vectors.
  
• These genes transcribe RNA molecules which form dsRNA, initiating RNAi in the plant.
  
• When the nematode feeds on the transgenic roots, the silencing RNA affects its gene expression, thus preventing its infection and development.

(a) The enzyme used in Step-1 is DNA ligase. It joins the sticky ends of the vector DNA and the alien DNA to form a recombinant DNA molecule.
(b) The technical term for Step-3 is transformation, which is the process of introducing recombinant DNA into the host cell (E. coli).
(c) Using the same restriction enzyme (EcoR I) to cut both vector and alien DNA ensures that both fragments have complementary sticky ends. This compatibility facilitates the easy and specific joining of the DNA fragments using DNA ligase, ensuring successful recombination.

Definition: Transgenic animals are those that carry a foreign gene that has been deliberately inserted into their DNA and is passed on to the next generation.

Key Points: The inserted gene may come from the same species or a different species. The purpose is to alter traits, produce medically useful products, or study gene functions. The transgene becomes a permanent part of the animal’s genetic material and is inherited by its offspring.

Examples: Transgenic mice for studying cancer and genetic disorders. Transgenic cows that produce human proteins in milk. Transgenic pigs for organ transplantation research. Transgenic goats producing therapeutic proteins.

Polymerase Chain Reaction (PCR)

Purpose: PCR is a powerful technique used to amplify a specific gene or DNA segment in vitro, producing millions of copies from a small initial sample.

Steps of PCR:

1. Denaturation:
   The DNA sample is heated to 94–98°C. This breaks the hydrogen bonds between the strands, converting double-stranded DNA into two single strands.
2. Annealing:
   The temperature is reduced to 50–65°C to allow short, single-stranded DNA primers to bind (anneal) to their complementary sequences on the template strands.
3. Extension:
   The temperature is increased to about 72–80°C, optimal for the thermostable enzyme Taq polymerase. This enzyme synthesizes the new DNA strand by adding nucleotides to the primers.
4. Amplification (Cycles):
   The above three steps are repeated for 20–40 cycles, resulting in an exponential increase in the number of DNA copies. After n cycles, ideally:

✅ Applications:

• Genetic testing and diagnostics
• Forensic science (DNA fingerprinting)
• Infectious disease detection
• Gene cloning and research

Making Bacterial Cells Competent for DNA Uptake

Bacterial cells can be made competent to take up recombinant DNA using two major methods:

1. Chemical Transformation

• Bacterial cells are treated with calcium chloride:
• This treatment increases the permeability of the bacterial cell membrane.
• The recombinant DNA can then pass through the cell membrane more easily.

2. Electroporation

• An electrical pulse is applied to the bacterial suspension.
• This creates temporary pores in the bacterial membrane.
• DNA molecules enter the cell through these pores.

3. Selection

• After transformation, bacterial cells are incubated on selective media.
• Only those cells that have successfully taken up the recombinant DNA will survive and grow.

(a) Proteins coded by which specific Bt. toxin gene control corn borer?
- The specific Bt. toxin gene that controls corn borer is the cry1Ab gene.
- The cry genes in code for proteins called Cry proteins (insecticidal proteins). The Cry1Ab protein is toxic to the larvae of the corn borer
(b) How does Bt. toxin produced by the bacterium kill the insect? Explain.
- The Cry protein produced by is ingested by the larvae of the corn borer when they feed on the Bt. cotton or Bt. corn.
- Once ingested, the Cry protein is activated in the insect's alkaline digestive system. The protein binds to specific receptors in the insect's gut cells, forming pores in the gut lining.
- These pores cause the gut cells to break down, leading to the loss of the gut's permeability, disrupting digestion. This results in the death of the insect due to starvation and septicemia.