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Zoology · Biotechnology and its Applications

Transgenic Animals

Transgenic animals — animals carrying and expressing a foreign gene — close Section 10.3 of NCERT Class 12 biology. The topic is a fact-recall favourite for NEET: the five-point list of uses, the dominance of mice, and named examples such as Rosie the 1997 cow are repeatedly assembled into match-the-column and statement-evaluation questions. Expect at least one cross-reference question every two-to-three years drawn from this single page of the textbook.

NCERT grounding

Section 10.3 of the NCERT Class 12 chapter Biotechnology and its Applications defines the term, lists the species in which transgenics have been produced, and enumerates five reasons for making them. Every sentence on this page has been mined for question stems — option strings such as "alpha-1-antitrypsin / emphysema", "Rosie / 2.4 grams per litre", and "polio vaccine safety / monkeys" are pulled verbatim into options. The corresponding NIOS lesson (Chapter 30, Section 30.8) adds methodology — microinjection into the male pronucleus and the retroviral vector route — which NEET occasionally uses for one-line traps.

"Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals."

— NCERT Class 12, Section 10.3

Five uses of transgenic animals

NCERT clusters the entire scientific rationale for transgenic animals into a numbered list of five applications. The wording on the textbook page is dense, but the five "buckets" are mutually exclusive and easy to memorise once you tie each one to a named example or a named disease. Confusing one bucket for another — for instance, dropping alpha-1-antitrypsin into "vaccine safety" instead of "biological products" — is the single most common mistake on this topic.

Read the five uses below as a checklist. For NEET, you should be able to produce the list cold, attach the right example to each entry, and recognise distractors built by swapping examples across buckets.

Memory hook (NCERT order): Physiology → Disease → Products → Vaccine → Chemical. "PDPVC" — physiology and development first, toxicity testing last.

1 · Normal physiology & development

Study how genes are regulated and how they affect normal functioning of the body and its development.

NCERT example: insulin-like growth factor (IGF). Genes from other species that alter IGF formation are introduced, and the resulting biological effects reveal the factor's role.

Bucket cue: "gene regulation / growth"

2 · Study of disease

Transgenic animals act as disease models, increasing understanding of how genes contribute to disease and enabling new treatments to be tested.

Four diseases on the NEET list: cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's.

Bucket cue: "models for human diseases"

3 · Biological products

Animals engineered to secrete human proteins (often in milk) that would otherwise be expensive to manufacture.

Three named products: α-1-antitrypsin (emphysema), human protein factor IX (haemophilia), human alpha-lactalbumin (Rosie, 1997).

Bucket cue: "milk / human protein"

4 · Vaccine safety

Transgenic mice are being developed to test the safety of vaccine batches before human use.

NCERT example: polio vaccine. If reliable, transgenic mice could replace monkeys for this purpose.

Bucket cue: "polio · replace monkeys"

5 · Chemical safety / toxicity testing

Same procedure as drug-toxicity testing. Animals carry genes that make them more sensitive to toxins than wild-type animals.

Outcome: faster results, fewer large animals — transgenic mice replace bigger species.

Bucket cue: "more sensitive · less time"

Why over 95 per cent of all transgenic animals are mice

NCERT records that transgenic rats, rabbits, pigs, sheep, cows and fish have all been produced, but writes plainly that over 95 per cent of existing transgenic animals are mice. This statistic is the highest-yield single fact on the page; it appears as a stand-alone option in match-the-column items. The reasons it is true are practical rather than biological — mice are not unique in their genetics, only in their usability.

>95%

NCERT key fact

"Over 95 per cent of all existing transgenic animals are mice." Rats, rabbits, pigs, sheep, cows and fish make up the remainder. Memorise the species list — NEET sometimes swaps in birds or amphibians as distractors.

The case for mice rests on five practical advantages. They are small (cheap to house), reproduce rapidly (short generation time), produce large litters (statistical power), have a fully sequenced genome (since 2002), and — crucially — their fertilised eggs are large enough to accept microinjection of foreign DNA into the male pronucleus without lethal damage. The retroviral vector route works in mouse pre-implantation embryos for the same anatomical reasons. Together these make mice the de-facto standard for the entire field.

Named transgenic animals and products

NEET options recycle the same handful of names. Hold all of these in active recall: Rosie (cow, 1997, human alpha-lactalbumin, 2.4 grams per litre); α-1-antitrypsin (treats emphysema); factor IX (treats haemophilia); and the four NCERT-listed disease models — cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's. NIOS adds transgenic goats (tissue plasminogen activator, tPA, dissolves blood clots for heart-attack and stroke patients) and Chinese hamster ovary cells (factor VIII, haemophilia A). NCERT itself names the rat IGF transgenic mouse only obliquely; treat it as an illustration of physiology research, not a stand-alone product.

Transgenic animal / cell Foreign gene / product Clinical use
Mouse (research staple)Rat IGF (insulin-like growth factor)Physiology / development studies
Sheep (NCERT)α-1-antitrypsinEmphysema
Sheep / livestock (NCERT)Human protein factor IXHaemophilia
Rosie (cow, 1997)Human alpha-lactalbumin (2.4 g/L)Nutritionally balanced milk for human babies
Transgenic goat (NIOS)Tissue plasminogen activator (tPA)Dissolves clots (coronary thrombosis, stroke)
Chinese hamster ovary cells (NIOS)Factor VIIIHaemophilia A (avoids HIV risk from human-blood factor)
Transgenic mouse (polio receptor)Human poliovirus receptorPolio vaccine safety testing (replaces monkeys)

How a transgenic animal is made (NIOS supplement)

NCERT does not narrate the method; NIOS Section 30.8 does. The classic procedure is microinjection of foreign DNA into the male pronucleus of a fertilised egg. The retroviral-vector route — infection of pre-implantation embryos with a retrovirus carrying the foreign DNA — is the alternative. The full microinjection workflow is summarised below; expect occasional NEET items asking which step uses what.

Pronuclear microinjection — eight steps (NIOS 30.8)

Most common route to mammalian transgenics
  1. Step 1

    Collect oocytes

    Recovered from female parent surgically or post-slaughter.

  2. Step 2

    In-vitro maturation

    Oocytes matured in culture before fertilisation.

  3. Step 3

    In-vitro fertilisation

    Fertilised with male semen in the dish.

  4. Step 4

    Centrifuge

    Concentrates yolk so the male pronucleus is visible.

  5. Step 5

    Microinjection

    100–1000 copies of the gene injected into the male pronucleus.

  6. Step 6

    In-vitro embryo development

    Embryos cultured to a transferable stage.

  7. Step 7

    Implant in foster mother

    Non-surgical implantation of one embryo.

  8. Step 8

    Screen offspring

    DNA of offspring screened for the transgene.

Figure 1 Pronuclear microinjection of foreign DNA Microinjection of foreign DNA into male pronucleus Holding pipette ♂ pronucleus ♀ Micropipette · foreign DNA 100–1000 copies of gene injected · embryo then cultured & implanted

Figure 1. The fertilised egg is immobilised on a holding pipette (left). A fine micropipette (right) delivers foreign DNA — typically 100 to 1000 copies of the transgene — into the larger male pronucleus. After microinjection, the embryo is cultured in vitro and then transferred non-surgically into a foster mother.

Ethical concerns (NEET reference level)

NCERT does not develop a separate ethical analysis for transgenic animals; the broader Section 10.4 — covered on a sibling page — applies. For NEET at this level, two points matter. First, the manipulation of living organisms cannot proceed unregulated, which is why India established the Genetic Engineering Appraisal Committee (GEAC) to approve GM research and the release of GM organisms (PYQ NEET 2018). Second, transgenic-animal production raises specific concerns about animal welfare, the unpredictability of off-target genome edits, and the equitable sharing of benefits from products derived from genetic material long used by traditional communities (the biopiracy theme). These remain general principles; deeper ethical analysis sits with the dedicated GEAC subtopic.

Worked examples

Worked example 1

Q. A transgenic cow named Rosie produced human protein-enriched milk. The protein concerned and the year of the achievement are, respectively:

A. Human alpha-lactalbumin, in 1997. NCERT records that the milk contained 2.4 grams per litre of this human protein and was nutritionally a more balanced product for human babies than natural cow milk. Distractors that pair Rosie with α-1-antitrypsin (a sheep example) or with factor IX (haemophilia) are common; the correct linkage is Rosie → alpha-lactalbumin → infant nutrition.

Worked example 2

Q. Statement I: Over 95 per cent of existing transgenic animals are mice. Statement II: Transgenic mice are used to test the safety of polio vaccines and could replace monkeys for this purpose. Which is correct?

A. Both statements are correct and both are NCERT statements. Statement I is the headline fact about why mice dominate the field; Statement II is one specific application — vaccine safety testing — given in NCERT Section 10.3 (iv). Mice are made transgenic for the human poliovirus receptor so they respond to the virus like primates do; this could replace monkey-based safety testing for polio vaccine batches.

Worked example 3

Q. Match the transgenic product with its clinical use: (A) α-1-antitrypsin (B) Factor IX (C) Alpha-lactalbumin (D) Tissue plasminogen activator. Choices: (I) Haemophilia (II) Emphysema (III) Dissolves blood clots (IV) Enriched milk.

A. A–II, B–I, C–IV, D–III. α-1-antitrypsin treats emphysema; factor IX treats haemophilia; alpha-lactalbumin enriched the milk of Rosie; tissue plasminogen activator from transgenic goats dissolves clots in coronary thrombosis. NEET 2024 used a similar A–B–C–D match with α-1-antitrypsin and Cry-genes — keep the product-to-use map intact in active recall.

Worked example 4

Q. Which of the following is not among the four human diseases for which transgenic models are listed in NCERT Section 10.3? Options: (1) cancer (2) cystic fibrosis (3) sickle-cell anaemia (4) Alzheimer's.

A. (3) sickle-cell anaemia. The four NCERT-listed transgenic disease models are cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's. Sickle-cell anaemia features elsewhere in the chapter (gene therapy / hereditary disease discussions) but is not on the transgenic-animal list. NEET frequently builds "all of the following except" stems on exactly this four-item set.

Common confusion & NEET traps

Bucket discrimination — biological products vs vaccine safety

Biological products (Use #3)

Produce a useful protein in the animal's body / milk

  • α-1-antitrypsin → emphysema
  • Factor IX → haemophilia
  • Alpha-lactalbumin → Rosie (1997, 2.4 g/L)
  • Attempts also for PKU, cystic fibrosis
vs

Vaccine safety (Use #4)

Use the animal as a sensitive testing system

  • Transgenic mice express viral receptors
  • Polio vaccine safety testing
  • If reliable, replaces monkeys
  • No human protein is harvested

NEET PYQ Snapshot — Transgenic Animals

Direct PYQs on transgenic animals are sparse; the NEET 2024 match item is the most recent direct hit, supplemented by the GEAC-linked 2018 question.

NEET 2024

Match List I with List II: A. α-1-antitrypsin · B. Cry IAb · C. Cry IAc · D. Enzyme replacement therapy  ||  I. Cotton bollworm · II. ADA deficiency · III. Emphysema · IV. Corn borer.

  1. A-II, B-I, C-IV, D-III
  2. A-III, B-I, C-II, D-IV
  3. A-III, B-IV, C-I, D-II
  4. A-II, B-IV, C-I, D-III
Answer: (3)

Why: α-1-antitrypsin is the transgenic biological product for emphysema (III). Cry IAb targets corn borer (IV); Cry IAc targets cotton bollworm (I); enzyme replacement therapy applies to ADA deficiency (II). One stem tests three of the chapter's flagship facts; the transgenic-animal anchor is the α-1-antitrypsin → emphysema pairing.

NEET 2018

In India, the organisation responsible for assessing the safety of introducing genetically modified organisms for public use is:

  1. Indian Council of Medical Research (ICMR)
  2. Council for Scientific and Industrial Research (CSIR)
  3. Research Committee on Genetic Manipulation (RCGM)
  4. Genetic Engineering Appraisal Committee (GEAC)
Answer: (4)

Why: GEAC is the statutory body cited in NCERT Section 10.4 — it clears all GM research and the release of GM organisms, including transgenic animals. RCGM is a different (research-stage) committee; ICMR and CSIR set their own ethics norms but are not the regulatory body for GM release.

Concept

Which one of the following statements about transgenic animals, as per NCERT Section 10.3, is incorrect?

  1. Over 95 per cent of all existing transgenic animals are mice.
  2. The first transgenic cow, Rosie, was produced in 1997.
  3. Rosie's milk contained 2.4 grams per litre of human alpha-lactalbumin.
  4. Transgenic mice are used to test the safety of vaccine batches and could replace pigs for polio vaccine testing.
Answer: (4)

Why: Option (4) plants a species swap — NCERT says transgenic mice could replace monkeys, not pigs, in polio vaccine safety testing. Options (1)–(3) reproduce the NCERT wording exactly and are correct.

Concept

Which of the following human diseases is not listed in NCERT as one having a transgenic animal model?

  1. Cancer
  2. Cystic fibrosis
  3. Rheumatoid arthritis
  4. Sickle-cell anaemia
Answer: (4)

Why: NCERT lists exactly four — cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's. Sickle-cell anaemia is treated elsewhere in the syllabus (genetic disorders, gene therapy) and is a common distractor in this "all except" pattern.

FAQs — Transgenic Animals

Definition, the dominance of mice, named examples, and the polio-vaccine substitution — all questions answer NCERT Section 10.3 directly.

What is a transgenic animal in one line as per NCERT?

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals (NCERT Class 12, Section 10.3). The introduced foreign gene is called the transgene.

Why are more than 95 percent of all transgenic animals mice?

Mice are small, breed rapidly, have a short generation time, produce large litters, are inexpensive to house, and their early embryos tolerate microinjection of foreign DNA into the male pronucleus. These practical advantages explain why over 95 percent of all existing transgenic animals are mice, even though transgenic rats, rabbits, pigs, sheep, cows and fish have all been produced.

What was special about Rosie the cow (1997)?

Rosie, born in 1997, was the first transgenic cow. She produced human protein-enriched milk containing 2.4 grams per litre of human alpha-lactalbumin. The enriched milk was nutritionally a more balanced product for human babies than natural cow milk because it carried a human nutritional protein.

Which human protein produced in transgenic animals is used to treat emphysema?

Alpha-1-antitrypsin (α-1-antitrypsin) is the transgenic biological product used to treat emphysema, a chronic lung disease. NCERT also lists similar transgenic attempts for phenylketonuria (PKU) and cystic fibrosis.

How do transgenic mice replace monkeys in polio vaccine safety testing?

Transgenic mice are engineered to express the human poliovirus receptor so that they respond to the virus much like primates. If a vaccine batch is safe in these mice, it can be deemed safe for humans. NCERT states that if this approach is reliable, transgenic mice could replace monkeys in testing the safety of polio vaccine batches.

What is chemical safety / toxicity testing using transgenic animals?

Transgenic animals are made that carry genes which render them more sensitive to toxic substances than non-transgenic animals. They are then exposed to the chemical and the effects studied. Because the response is amplified, results are obtained in less time and with fewer animals than conventional drug-toxicity testing.

What are the five uses of transgenic animals listed in NCERT?

NCERT Section 10.3 lists five uses: (i) Normal physiology and development, (ii) Study of disease — models of cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's, (iii) Biological products — alpha-1-antitrypsin, human protein factor IX, human alpha-lactalbumin, (iv) Vaccine safety — polio vaccine testing in transgenic mice, and (v) Chemical safety / toxicity testing.

Related Topics
Biotechnology and its Applications Back to the full chapter notes. Ethical Issues & GEAC Regulation of GM research and biopiracy. Biotech in Medicine Therapeutic and diagnostic applications. Genetically Engineered Insulin Humulin in E. coli — Eli Lilly, 1983. Gene Therapy ADA deficiency and retroviral correction. Molecular Diagnosis — ELISA & PCR Early disease detection techniques. Bt Cotton & Pest-Resistant Plants Cry I Ab and Cry I Ac — transgenic plants.