Q.Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Recombinant Protein Therapeutics
Imagine you need a specific medicine—say, insulin for diabetes—but the only way to get it used to be from the pancreas of cows or pigs. That was expensive, risky (animal proteins could trigger allergies), and never quite identical to human insulin. Now, we can take the human gene that makes insulin, put it into a harmless bacterium or yeast, and let that microbe churn out perfect human insulin in huge vats. That is the core idea of recombinant protein therapeutics.
Recombinant means "made by combining DNA from different sources." Protein therapeutics means "a protein used as a medicine." So, recombinant protein therapeutics are medicines that are proteins, made by genetically engineered living cells, to treat or prevent disease.
The NCERT textbook (Class 12 Biology, Chapter 12, Biotechnology and its Applications) introduces this under "Biotechnological Applications in Medicine." It specifically mentions human insulin (Humulin) as the first recombinant therapeutic approved for human use. The textbook explains that the human insulin gene was inserted into E. coli bacteria, which then produced insulin identical to our own.
How does it work, step by step?
- Identify the gene that codes for the therapeutic protein (e.g., the gene for human insulin, growth hormone, or clotting factor).
- Insert that gene into a "vector" (a carrier DNA, often a plasmid from a bacterium) using restriction enzymes and DNA ligase.
- Introduce the vector into a host cell (usually E. coli bacteria, yeast, or mammalian cells). This host cell is now "transformed" – it carries the human gene.
- Grow the host cells in large fermenters. As they multiply, they follow the human gene's instructions and produce the human protein.
- Purify the protein from the culture. The final product is a pure, human-identical therapeutic protein, free from animal contaminants.
Why does this matter? (The "why" for a commerce/humanities student)
- Safety and Efficacy: Because the protein is exactly human, the body rarely rejects it. No risk of animal viruses or allergic reactions to animal proteins.
- Scalability: You can produce massive quantities in a lab, independent of animal supply. One batch of engineered bacteria can make more insulin in a day than thousands of pig pancreases.
- Cost (eventually): While initial R&D is expensive, mass production drives down cost, making life-saving drugs accessible to more people.
- New Treatments: It enables therapies that were impossible before—like monoclonal antibodies for cancer, or erythropoietin for anaemia in kidney patients.
The NCERT textbook emphasises that recombinant therapeutics are "relatively free from risk of infection and immune response" compared to products extracted from animals or human cadavers. This is the single biggest advantage: purity and human compatibility.
Examples you should know (from NCERT and common knowledge) …
Insulin is first made as a longer precursor, pro-insulin, which must be processed before it becomes functional — a key example in the NCERT Class 12 Biology chapter on biotechnology and its applications (genetically engineered insulin). …
Pro-insulin becomes mature insulin by the removal of the C-peptide (the connecting peptide), leaving the A and B chains linked by disulphide bonds.
Concept. Insulin is a peptide hormone made of two short polypeptide chains, A and B, held together by disulphide bridges. In humans (and mammals) it is synthesised first as a pro-hormone (pro-insulin) that needs processing to become fully mature and functional.
Why the change is needed. Pro-insulin contains an extra polypeptide stretch — the C-peptide — in addition to the A and B chains. This extra peptide is not present in the mature, functional hormone.
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- KCET 2026Set UNKNOWN1 markMCQQ.The human protein obtained from transgenic animals used to treat emphysema is (A) Insulin (B) α - Lactalbumin (C) α - 1 antitrypsin (D) β - Lactalbumin
›Reveal solutionSolution
Human α-1 antitrypsin, produced from transgenic animals (e.g., sheep engineered to secrete it in their milk), is used to treat emphysema.
Step 1 — Transgenic animals as protein factories
Transgenic animals can be engineered so that the gene responsible for a desired human protein is introduced along with regulatory sequences that direct its expression into milk, allowing large-scale, easy purification of the protein.
Step 2 — The specific example: α-1 antitrypsin …
- KCET 2024Set B-41 markMCQQ.If a recombinant DNA bearing gene for resistance to Ampicillin is transferred into E.coli cells, host cells become transformed into Ampicillin resistant cells. What happens when these E.coli are grown on medium containing Ampicillin ? (A) Non-transformants will grow and transformants will die (B) Non-transformants will die and transformants will grow (C) Both non-transformants and transformants will die (D) Both non-transformants and transformants will grow
›Reveal solutionSolution
Ampicillin resistance is a selectable marker: on an ampicillin plate it kills every cell that did not take up the plasmid, leaving only transformants alive.
Step 1 — What a selectable marker is and why a vector carries one.
Transformation is a very inefficient process — out of a huge population of bacteria only a tiny fraction actually take up the foreign DNA. To find them, the vector carries a selectable marker: a gene that lets the researcher identify and eliminate non-transformants and selectively permit the growth of the transformants.
Genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin are the classic markers, because normal E. coli cells do not carry resistance against these antibiotics.
Step 2 — Trace what happens to each cell type on an ampicillin plate.
- A transformant has taken up the recombinant DNA, which carries the ampR gene. It therefore expresses β-lactamase, which hydrolyses the β-lactam ring of ampicillin and inactivates the drug. Ampicillin normally kills bacteria by blocking cell-wall (peptidoglycan) synthesis; with the drug destroyed, the cell builds its wall normally and grows and divides, forming a colony. ✓
- A non-transformant never received the plasmid, has no ampR gene, cannot inactivate ampicillin, so its cell-wall synthesis is blocked and it dies. ✗
Ampicillin plate⟹transformants survive,non-transformants die
The colonies that appear are, by construction, exactly the cells that took up the recombinant DNA — which is the whole point of the design.
Step 3 — Eliminate the other options. …
- KCET 2022Set A-11 markMCQQ.ADA deficiency can be cured by (A) Kidney Transplantation (B) Bone-marrow Transplantation (C) Heart Transplantation (D) Liver Transplantation
›Reveal solutionSolution
ADA deficiency cripples the immune system's lymphocytes, so the cure must replace the blood-forming stem cells — i.e. a bone-marrow transplant.
Step 1 — What ADA deficiency is
Adenosine deaminase (ADA) deficiency is caused by the deletion of the gene for adenosine deaminase. The enzyme is essential for the normal function of lymphocytes; without it, toxic metabolites accumulate and the lymphocytes die. The result is SCID — severe combined immunodeficiency — the child has essentially no working immune system.
Step 2 — Why the bone marrow is the target
Lymphocytes (both B and T cells) are produced from haematopoietic stem cells residing in the bone marrow. So the defective cell lineage lives in the marrow. Replacing that marrow with a compatible donor's marrow replaces the stem-cell pool with cells carrying a functional ADA gene, which then generate healthy lymphocytes for life.
The NCERT statement is explicit: "ADA deficiency can be cured by bone marrow transplantation."
Step 3 — The three NCERT approaches, ranked
- Bone-marrow transplantation — the only curative option, but it needs a compatible donor and is not always available.
- Enzyme replacement therapy — functional ADA is injected; not completely curative, since the enzyme must be given repeatedly. …
- KCET 2021Set C-31 markMCQQ.Rop-gene which codes of the proteins involved in the replication of the plasmid pBR322 in E.coli is located at restriction site of (A) Hind III (B) EcoRI (C) Pvu II (D) BamH I
›Reveal solutionSolution
On the standard pBR322 map the restriction site falling within the rop gene is Pvu II; Hind III, EcoR I and BamH I lie elsewhere (in/near the tetR region).
Step 1 — Recall the anatomy of pBR322
pBR322 is the classic E. coli cloning vector. Its essential features are:
- ori — origin of replication; controls copy number.
- rop — codes for the proteins involved in the replication of the plasmid (exactly the phrase used in the question stem).
- ampR and tetR — two selectable (antibiotic-resistance) markers.
- A set of unique restriction sites — the places a foreign DNA insert can be introduced.
Step 2 — Where each restriction site sits
- Hind III, EcoR I, BamH I, Sal I — these cluster in/around the tetracycline-resistance (tetR) region; inserting DNA there inactivates tetR (insertional inactivation). …
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