Recombinant DNA Technology Class 12 is Chapter 1 of the NCERT Biotechnology textbook for the current academic session — an eight-page overview of how scientists learned to cut, join and move DNA between organisms.
The official chapter PDF is right below, and the rest of this page explains what the chapter contains and teaches, so you know where to read carefully and what to revise.
Download the Recombinant DNA Technology Class 12 NCERT PDF
NCERT publishes this chapter as the file lebt101.pdf on its official website. The file holds the complete chapter exactly as printed — the unit contents, the Herbert Boyer biography, section 1.1, the Box 1 history timeline, the Summary and the closing exercise set.
Download the NCERT Class 12 Biotechnology Chapter 1 Recombinant DNA Technology PDF to read the chapter on your phone or laptop while you work through the explanations below, or to save it for offline revision before class.
| What the chapter holds | Count | Where it is used |
|---|---|---|
| Printed pages | 8 | |
| Sections in the chapter | 2 | |
| Figures with NCERT captions | 1 | |
| Tables | 2 | |
| Exercise questions | 6 | answered in our NCERT Solutions |
| Official NCERT PDF | Download the chapter PDF | the chapter exactly as NCERT publishes it |
Chapter at a Glance
The table on this page gives the chapter’s size at a glance — how many sections, figures and exercise questions it holds — from the same official source as the PDF. It is the fastest way to judge how much reading Chapter 1 involves before you start.
Despite the technical title, this is an overview chapter: it introduces vocabulary and history, sets up the other three chapters of the unit, and closes with a short exercise set. There are no formulas and no numerical problems to practise.
What This Chapter Covers
NCERT has organised Chapter 1 as a deliberately short introduction. It gives you the vocabulary and history you need for the rest of the unit; the practical detail follows in later chapters. The chapter’s own closing line in Box 1 says as much: the next chapters of the unit discuss the components and applications of rDNA technology in detail (NCERT, p. 6).
- Unit contents (p. 1): the unit lists four chapters — Chapter 1, An Overview of Recombinant DNA Technology; Chapter 2, Host–Vector System; Chapter 3, Gene Cloning; and Chapter 4, Application of Recombinant DNA Technology.
- Herbert Boyer (p. 2): a biography of the researcher who co-created the first genetically modified organisms.
- Section 1.1 (pp. 3–5): the body of the chapter — the definition, the science that made rDNA technology possible, the molecular tools, and the applications in medicine and agriculture.
- Box 1 (p. 6): the chapter’s timeline of 28 landmark discoveries from 1917 to 2023.
- Summary (p. 7): NCERT’s two takeaway points — the definition of rDNA technology and the idea of gene cloning.
- Exercises (p. 8): a closing set of discussion, factual MCQ and assertion–reason questions.
The biography on page 2 is unusual for a textbook. Herbert ‘Herb’ Boyer was born in 1936 in Derry, Pennsylvania, trained in microbial genetics at the University of Pittsburgh, later co-founded Genentech, and received the 1996 Lemelson-MIT Prize.
The chapter tells his story because the 1973 Cohen–Boyer experiment — cutting open a plasmid, inserting a gene from another species, and closing the plasmid again — produced the first genetically modified organisms (NCERT, p. 2). Who did what matters: the exercise set asks about it directly.
Section 1.1 ends by pointing to Box 1, the chapter’s record of the landmark discoveries that built modern biotechnology. This is the most fact-dense part of the chapter and the source of its factual MCQs. The timeline below follows the book’s entries, grouped under four heads: foundations, tools, products and genome editing.
| Year | Milestone | Stage |
|---|---|---|
| 1917 | Karl Ereky coined the term ‘Biotechnology’ | Foundations |
| 1944 | Avery, MacLeod and McCarty demonstrated that ‘DNA is the genetic material’ | Foundations |
| 1952 | Joshua Lederberg discovered ‘Plasmids’ | Foundations |
| 1953 | Watson and Crick proposed the ‘Double Helical structure of DNA’ | Foundations |
| 1960s | Werner Arber and Matthew Meselson discovered ‘Type I restriction enzymes’ | Tools |
| 1967 | Gellert, Lehman, Richardson and Hurwitz discovered ‘ligase enzymes’ | Tools |
| 1970 | Hamilton O. Smith and Thomas J. Kelly discovered ‘Type II restriction enzymes’ | Tools |
| 1972 | Paul Berg assembled the first ‘Recombinant DNA’ from a bacterium into a virus | Tools |
| 1973 | Stanley N. Cohen and Herbert Boyer developed ‘DNA cloning and rDNA technology’ | Tools |
| 1975 | Georges J.F. Köhler and César Milstein described ‘Hybridoma Technology’ for production of monoclonal antibodies | Tools |
| 1982 | FDA approved the world’s first recombinant DNA therapeutic product, ‘Humulin’, developed by Eli Lilly and Genentech | Products |
| 1983 | Kary Mullis developed ‘Polymerase Chain Reaction’ | Tools |
| 1984 | Sir Alec Jeffreys invented ‘DNA Fingerprinting’ | Tools |
| 1986 | The first recombinant vaccine, ‘Recombivax HB’ for Hepatitis B, was approved for human use | Products |
| 1990 | The ‘Human Genome Project’ was officially initiated, coordinated by the U.S. Department of Energy and the National Institutes of Health | Genome editing |
| 1994 | The first genetically engineered crop, ‘Flavr Savr’ tomato, was introduced (produced by Calgene in 1992) | Products |
| 1996 | Keith Campbell and Ian Wilmut cloned the first mammal, ‘Dolly’ the sheep, from a somatic cell using nuclear transfer | Genome editing |
| 1996 | Researchers at Monsanto developed ‘Bt cotton’; first commercially released in China and the United States, followed by India in 2003 | Products |
| 2000 | Ingo Potrykus and Peter Beyer developed ‘Golden Rice’ | Products |
| 2003 | The Human Genome Project (HGP) was completed | Genome editing |
| 2004 | ‘Avastin’, an anti-VEGF monoclonal antibody for cancer treatment, was developed | Products |
| 2006 | Recombinant vaccine ‘Gardasil’ against human papillomavirus (HPV) received FDA approval | Products |
| 2006 | Nobel prize awarded for the discovery of RNA interference ‘Gene Silencing’ by double-stranded RNA | Genome editing |
| 2010 | Robert Edwards awarded Nobel Prize for the development of human ‘in vitro fertilization’ (IVF) therapy | Genome editing |
| 2012 | Shinya Yamanaka and John B. Gurdon discovered that mature differentiated cells can be reprogrammed into ‘Induced Pluripotent Stem Cells’ | Genome editing |
| 2019 | Nobel prize awarded for the discovery of the ‘CRISPR-Cas9’ genome editing tool | Genome editing |
| 2020 | Recombinant vaccines against COVID-19 were developed | Products |
| 2023 | Nobel prize awarded for the mRNA vaccine against COVID-19 | Genome editing |
The fourth group gathers the genome-level achievements of recent decades — whole-genome projects, gene silencing, genome editing and related Nobel-recognised advances. Read the table once in order and the chapter writes its own story: understand DNA first, then build tools, then produce things with them.
Key Concepts in This Chapter
This is the part to actually understand, because every later chapter of the unit builds on these ideas. Read each concept once with the NCERT page open beside you, and you will meet all of them again in Chapters 2–4.
What Recombinant DNA Technology Is
Recombinant DNA (rDNA) technology is the collective name for the methods used to directly manipulate the nucleic acid — the genome — of an organism. The chapter says plainly that the same methods are also called genetic engineering (NCERT, p. 3). The word ‘recombinant’ describes the result: genetic material put together in a new combination.
Section 1.1 makes a careful point: rDNA technology was not a single invention. It became possible only after a chain of discoveries in the last century (NCERT, p. 3):
- Proof that DNA carries an organism’s genetic information and passes it to the next generation.
- The determination of the chemical and physical structure of DNA — the double helix.
- A detailed understanding of replication, transcription and translation.
- Methods to isolate and purify DNA from organisms.
- Finally, the sequencing of DNA.
Each step was necessary. You cannot move a gene until you know what it is made of, how it is copied, and how to extract it cleanly. With that toolkit in place, scientists could ask a new question: is it possible to transfer a gene of interest from one organism to another and obtain its product?
The Molecular Tools: Restriction Enzymes and Ligase
Two enzymes do the physical work of moving DNA. Restriction enzymes act as scissors to cut DNA molecules; ligase is the enzyme that joins two DNA fragments (NCERT, p. 3). Cut with one, join with the other — that is the whole manoeuvre.
The two were discovered within a few years of each other. Ligase was found in 1967 by Gellert, Lehman, Richardson and Hurwitz. Restriction enzymes came from Werner Arber, Hamilton Smith and Daniel Nathans in the late 1960s and early 1970s (NCERT, p. 3).
Box 1 adds detail the body text does not: Type I restriction enzymes were discovered in the 1960s by Arber and Matthew Meselson, and Type II restriction enzymes in 1970 by Hamilton O. Smith and Thomas J. Kelly (NCERT, p. 6).
Why do the two tools matter? Without scissors you cannot remove a gene from its original DNA; without glue you cannot fasten it into its new carrier.
Boyer’s special skill, the chapter notes, was using restriction enzymes to cleave double-stranded DNA so that it produced single-stranded ends with identical termini — cut ends that can match the cut ends of another fragment, ready for the joining step (NCERT, p. 3).
The Cohen-Boyer Experiment, Step by Step
Chapter 1 tells the story of the first recombinant organisms as a partnership of two skills. Stanley Cohen could introduce plasmid DNA into E. coli and propagate and clone the plasmids inside the bacteria. Herbert Boyer could cleave double-stranded DNA with restriction enzymes. Put together, the two skills became rDNA technology (NCERT, p. 3).
- Start with a plasmid. A plasmid is a loop of DNA inside a bacterium. The chapter’s timeline credits Joshua Lederberg with discovering plasmids in 1952 (NCERT, p. 6).
- Cohen’s expertise prepares the carrier. Plasmid DNA can be introduced into E. coli, where it is propagated and cloned — so there is a working system to carry foreign DNA.
- Boyer’s expertise cuts the DNA. Restriction enzymes cleave double-stranded DNA, producing single-stranded ends with identical termini.
- Cut open the plasmid loop from one species of bacteria.
- Insert a gene from a different bacterial species into the opened loop.
- Close the plasmid again — ligase is the enzyme that joins the DNA fragments (NCERT, p. 3).
- Result: a recombinant plasmid carrying recombined DNA from two different sources — the first genetically modified organisms (NCERT, p. 2).
The chapter dates the experiment to 1973, after preliminary experiments that year, and Box 1 places it in sequence: in 1972 Paul Berg assembled the first recombinant DNA; in 1973 Cohen and Boyer developed DNA cloning and rDNA technology (NCERT, pp. 2, 6).
The Cohen–Boyer experiment matters because it proved the basic recipe of genetic engineering — cut a carrier, insert a foreign gene, close the carrier, let a host cell multiply it. Every product later in the chapter follows a version of that recipe.
Where rDNA Technology Is Applied
Two application areas anchor the applied half of the chapter: medicine and agriculture (NCERT, pp. 4–5). The logic is the same in both — a product that is hard, costly or risky to obtain from its natural source can be made in a controlled system using rDNA technology.
The chapter’s strongest example is the replacement of animal-derived insulin and growth hormone with safer bacterial versions. The table below compares the old route with the rDNA route.
| Product | Old animal source | Why it failed | rDNA solution |
|---|---|---|---|
| Insulin (treats diabetes) | Tons of animal pancreatic glands were needed to get only a few milligrams of insulin. | Available in limited quantity and at high cost, and the purified animal protein caused immunogenic reactions in humans. | Human insulin produced in a bacterial system using rDNA technology. |
| Growth hormone (treats dwarfism) | Thousands of animal pituitary glands were required to isolate the hormone. | The same three problems — limited quantity, high cost, immunogenic reactions. | Human growth hormone produced in a bacterial system. |
The chapter adds three more therapeutic products: interferon, used to treat cancer, and plasminogen activator and urokinase, used to dissolve blood clots (NCERT, p. 4). In agriculture, rDNA technology has produced genetically modified crops with targeted changes in their genomes: crops resistant to disease, so farmers worry less about crop damage, and drought-resistant or salinity-tolerant crops that grow in adverse environments.
These modifications improve both the quality and the value of production (NCERT, pp. 4–5).
The chapter also looks forward: a variety of important therapeutic proteins, peptides and hormones will increasingly be produced from plants using rDNA technology. The advantage over animal-based products is cost and contamination — animal products are costlier and need extra care to keep them free of viruses and other animal protein contaminants (NCERT, p. 5).
Figure Walkthrough: The Chapter Opening Image
The chapter’s opening image is titled ‘An Overview of Recombinant DNA Technology’. It stands at the head of section 1.1 (NCERT, p. 3), exactly where the text first defines rDNA technology as the direct manipulation of an organism’s genome.
Read the image as a diagram of that definition: genetic material being taken from one context, altered, and put together in a new combination. That is the same idea the Cohen–Boyer experiment performs with a plasmid and a foreign gene.
The figure also signals the chapter’s two halves — the science that built the technology, and the products it is used for. When you revise, try to state the chapter’s subject in one sentence; the figure is the book’s own attempt to give you that sentence visually.
Definitions You Should Know
These are the terms the chapter expects you to carry into later chapters. The NCERT page is given beside each term so you can check the exact wording in the book.
| Term | Plain meaning | NCERT page |
|---|---|---|
| Recombinant DNA (rDNA) technology | Methods used to directly manipulate the nucleic acid/genome of an organism | p. 3 |
| Genetic engineering | Another name for rDNA technology — the same definition | p. 3 |
| Gene cloning | Isolation and propagation of a desired DNA molecule (gene) from a source, to obtain its product in ample quantity | p. 7 |
| Plasmid | A loop of DNA inside bacteria that can carry foreign DNA; discovered by Joshua Lederberg in 1952 | pp. 3, 6 |
| Restriction enzymes | Enzymes that act as scissors to cut DNA molecules | p. 3 |
| Ligase | The enzyme that joins two DNA fragments | p. 3 |
| Recombinant plasmid | A plasmid carrying recombined DNA from two different sources — the product of the Cohen–Boyer experiment | p. 2 |
Common Mistakes Students Make in This Chapter
Most of the errors students make in this chapter come from a small set of confusions. The table names each one before you make it, gives the correct rule, and tells you how to check your answer.
| Mistake | Correct rule | How to check your answer |
|---|---|---|
| Thinking rDNA technology began with the double helix in 1953 | The double helix was one step, not the finish. Understanding replication, transcription and translation, isolating and purifying DNA, and sequencing all had to follow before the first recombinant DNA was assembled in 1972 and the first recombinant organisms were made in 1973. | List the foundations in order, then check that the 1972 and 1973 dates come at the end. |
| Mixing up restriction enzymes and ligase | Restriction enzymes cut DNA (scissors); ligase joins two DNA fragments (glue). | Ask: is this DNA being separated or put together? |
| Confusing gene cloning with cloning Dolly the sheep | Gene cloning isolates and propagates one DNA molecule (a gene) to get its product in quantity (NCERT, p. 7). Dolly was a whole mammal cloned from a somatic cell by nuclear transfer in 1996. | Ask: is the result a gene product or a whole organism? |
| Assuming animal insulin and growth hormone were replaced only because of cost | The chapter also gives limited quantity and immunogenic reactions in humans as reasons. | Name all three problems, not just cost. |
| Exercise Q5: choosing (a) because both statements are true | Both the assertion and the reason are true, but the reason (restriction endonuclease is a type of nuclease) does not explain the assertion. The correct answer is (b). | Read the reason as an explanation: does it tell you why the assertion is true? Naming a wider category is not an explanation. |
| Exercise Q6: treating it like Q5 and choosing (b) | Both statements are true, and this time the reason (the multifork replication mechanism) is the correct explanation of the assertion. The correct answer is (a). | Compare the two questions: in Q6 the reason names the mechanism that makes the assertion possible; in Q5 it only restates a category. |
Exam Notes: How to Revise This Chapter
One honest caution before exam preparation: textbook contents and the examinable syllabus are not always identical, so check the current official CBSE syllabus for Class 12 Biotechnology. Nothing on this page promises which specific questions will appear.
The chapter’s exercise set (NCERT, p. 8) has three question types, and each type draws on a different part of the chapter. The map below shows where each answer lives.
| Exercise | Type | What it tests | Where the answer lives |
|---|---|---|---|
| Q1 | Short discussion | How recombinant DNA technology was initially developed | Section 1.1, NCERT pp. 3–4 — the chain of discoveries plus the Cohen–Boyer experiment |
| Q2 | Short discussion | Applications in crop improvement and therapeutics | NCERT pp. 4–5 — the improved crops and the five named therapeutic products |
| Q3 | Factual MCQ | Who discovered the plasmid | Box 1, NCERT p. 6 — Joshua Lederberg, 1952 (option c) |
| Q4 | Factual MCQ | What plasminogen activator and urokinase are used as | NCERT p. 4 — a blood clot dissolving drug (option b) |
| Q5 | Assertion–reason | Restriction endonucleases | NCERT p. 3 and Box 1, p. 6 — answer (b) |
| Q6 | Assertion–reason | E. coli division and DNA replication | The question itself, NCERT p. 8 — answer (a) |
For the two discussion questions, a full answer names steps, not just conclusions. Q1 should move chronologically through the discoveries that laid the foundation — DNA as genetic material, the double helix, replication, transcription and translation, isolation and purification, sequencing — and end with the Cohen–Boyer experiment.
Q2 must cover both halves the question asks, with at least one named product for each: a disease-resistant, drought-resistant or salinity-tolerant crop for crop improvement, and insulin (or any of the other four therapeutics) for medicine.
For the factual MCQs, learn the Box 1 timeline, especially who discovered what and in which year. For the assertion–reason items, the trap is deciding whether the reason explains the assertion, not merely whether both statements are true. With no numerical problems in the chapter, revision here is about names, years and sequences.
Revision Summary: The Chapter in a Page
NCERT’s own Summary (NCERT, p. 7) distils Chapter 1 into two statements, worth memorising in your own words:
- rDNA technology equals genetic engineering. Both names mean the methods used to manipulate the nucleic acid/genome of an organism.
- Gene cloning. The isolation and propagation of a desired DNA molecule (gene) from a source, so that its product can be obtained in ample quantity.
The one breakthrough to remember: in 1973, Cohen and Boyer cut open a plasmid loop from one bacterial species, inserted a gene from a different species, and closed the plasmid — creating a recombinant plasmid and the first genetically modified organisms. Paul Berg’s 1972 recombinant DNA was the step immediately before it.
The two payoffs to remember: the therapeutic products (human insulin, human growth hormone, interferon, plasminogen activator, urokinase) and the improved crops (disease-resistant, drought-resistant, salinity-tolerant).
Five years carry this chapter’s story. Link them as a sequence:
| Year | What happened | Memory hook |
|---|---|---|
| 1944 | Avery, MacLeod and McCarty showed DNA is the genetic material | 1944 — prove the material |
| 1952 | Joshua Lederberg discovered plasmids | 1952 — find the carrier |
| 1953 | Watson and Crick proposed the double helical structure of DNA | 1953 — learn its shape |
| 1972 | Paul Berg assembled the first recombinant DNA | 1972 — build the first recombinant DNA |
| 1973 | Cohen and Boyer developed DNA cloning and rDNA technology | 1973 — make the technology work |
The hook in one line: 1944 prove the material (DNA), 1952 find the carrier (plasmid), 1953 learn its shape (double helix), 1972 build the first recombinant DNA, 1973 make the first recombinant organisms. Place the product years around them: 1982 Humulin, 1983 PCR, 2000 Golden Rice, 2019 CRISPR-Cas9.
Related Resources: The Full Book and Next Chapters
This listing is maintained for the 2026-27 academic session using the NCERT textbook information available to us. NCERT remains the authority for confirming the latest edition.
Chapter 1 is the overview for a four-chapter unit, and the official NCERT website ncert.nic.in hosts the official textbook files for the current edition. The rest of the unit continues directly from this chapter:
- Host–Vector System (Chapter 2) — the next chapter, which builds directly on the plasmid concept introduced here.
- Class 12 Biotechnology notes — chapter-wise help for the whole book.
- Class 12 notes hub — notes for every subject, not only Biotechnology.
- CBSE notes library — the full collection across classes.
Reference: NCERT Class 12 Biotechnology textbook, chapter 1, official edition on ncert.nic.in.
Sources and Data Verification
The page count and chapter structure on this page describe the NCERT Class 12 Biotechnology textbook, Chapter 1 (Recombinant DNA Technology), official edition as published on ncert.nic.in. This page covers that one chapter only — not the other three chapters of the unit and no other Class 12 subject.
This page is maintained for the current academic session using the NCERT edition available on ncert.nic.in. NCERT settles textbook editions, contents and official PDFs; CBSE settles the curriculum, syllabus and examinations. The two are different documents: a chapter appearing in the textbook does not by itself prove what is examinable this session.
No independent expert review is claimed for this page; every fact above traces to the textbook itself or to the official NCERT PDF linked at the top of the page.
FAQs: Recombinant DNA Technology Class 12
What is recombinant DNA technology in simple words?
It is the direct manipulation of an organism’s nucleic acid — its genome — to create a new combination of genetic material, which is why the same methods are also called genetic engineering (NCERT, p. 3). In practice it means cutting DNA, joining a gene from one source into a carrier, and letting a host cell produce the gene’s product.
Who discovered the plasmid?
Joshua Lederberg discovered plasmids in 1952, according to the chapter’s Box 1 timeline (NCERT, p. 6). That makes (c) Joshua Lederberg the correct answer to Exercise Q3 — the other options, Paul Berg, Sir Alec Jeffreys and Kary Mullis, are names from other milestones in the same timeline.
Why are restriction enzymes called molecular scissors?
Because their job is to cut DNA molecules, precisely the way scissors cut a thread. The chapter itself uses the comparison, describing restriction enzymes as acting like scissors to cut the molecules of DNA (NCERT, p. 3). They were discovered in the late 1960s and early 1970s by Werner Arber, Hamilton Smith and Daniel Nathans.
What is the difference between gene cloning and cloning Dolly the sheep?
Gene cloning isolates and propagates one desired DNA molecule (a gene) from a source so that its product can be made in ample quantity (NCERT, p. 7). Cloning Dolly, in 1996, produced a whole sheep from a somatic cell using nuclear transfer (NCERT, p. 6). Gene cloning copies a gene; Dolly is whole-organism cloning.
Which therapeutic products mentioned in this chapter are made using rDNA technology?
The chapter names five: human insulin and human growth hormone produced in bacterial systems, interferon used to treat cancer, and plasminogen activator and urokinase used to dissolve blood clots (NCERT, p. 4). Insulin and growth hormone get the most space because their animal-derived versions were costly, limited and caused immunogenic reactions.
Is this chapter still part of the CBSE Class 12 Biotechnology syllabus?
The NCERT Class 12 Biotechnology textbook still carries Recombinant DNA Technology as Chapter 1. Whether every part of it is examinable this session is a separate question — textbook contents and the examinable syllabus are not always identical — so check the current official CBSE syllabus for Class 12 Biotechnology before you decide how much to revise.
Explore Class 12 Biotechnology Books
Related chapters:
- Gene Cloning
- Applications of Recombinant DNA Technology
- Genome Engineering