BiologyCBSE Class 12 · Biotechnology and its Applications

Transgenic Animals

Updated 15 October 2026 · Fact-checked

Transgenic animals have had their DNA manipulated to carry and express an extra (foreign) gene. Over 95 per cent are mice. They are used to study normal physiology and development, as models of human diseases, to produce biological products such as α-1-antitrypsin or Rosie the cow's human protein-enriched milk, and to test the safety of vaccines and chemicals.

Notice that one animal with an added foreign gene serves five purposes; remember that over 95 per cent of transgenic animals are mice.

Illustration drawn for QuestionBuddy.

Understand Transgenic Animals

What they are. Animals whose DNA has been manipulated to possess and express an extra (foreign) gene are transgenic animals. Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced, but over 95 per cent of all transgenic animals are mice.

Why they are made: five uses.
1. Normal physiology and development: to study how genes are regulated and how they affect normal body functions and development. Example: studying complex growth factors such as insulin-like growth factor: genes from other species that alter its formation are introduced and the effects studied, revealing the factor's biological role.
2. Study of disease: transgenic animals serve as models for human diseases, so new treatments can be investigated. Models exist for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's.
3. Biological products: medicines may need biological products that are expensive to make. Introducing the gene for a product lets animals make it. Example: human α-1-antitrypsin, used to treat emphysema. Work on similar products is under way for cystic fibrosis and phenylketonuria (PKU). Rosie (1997), the first transgenic cow, gave milk enriched with a human protein, alpha-lactalbumin, at 2.4 g per litre; such milk is nutritionally better balanced for human babies than ordinary cow milk.
4. Vaccine safety: transgenic mice are used to test vaccine safety before human use; e.g. polio vaccine safety. If reliable, this could replace the use of monkeys to test vaccine batches.
5. Chemical safety testing (toxicity testing): animals carrying genes that make them more sensitive to toxic substances are exposed to chemicals and the effects studied, giving results in less time, as in drug toxicity testing.

How a transgene gets in (general idea). A gene of interest is introduced into the animal's cells, typically at a very early stage (e.g. into a fertilised egg by micro-injection into the nucleus), so that the animal and its offspring carry and express it. Disarmed retroviruses can also deliver genes into animal cells.

Ethics and regulation. Genetic modification of organisms can have unpredictable results when they are introduced into ecosystems. The Indian Government has set up the Genetic Engineering Approval Committee (GEAC), which judges whether GM research is valid and whether releasing GM organisms for public use is safe. Using animals for products also raises questions about their welfare.

Flow chart (biological product): human gene for a protein → introduced into the animal (e.g. fertilised egg) → transgenic animal → protein secreted (e.g. in milk) → extracted and purified → medicine or food supplement.

Draw and label: uses of transgenic animals (concept map). Checklist: a central oval 'transgenic animals (95% mice)' with five spokes: 'normal physiology (insulin-like growth factor)', 'disease models (cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's)', 'biological products (α-1-antitrypsin; Rosie's milk with α-lactalbumin)', 'vaccine safety (polio vaccine; replaces monkeys)', 'chemical safety (toxicity testing)'. Labels as in the spokes.

Transgenic Animals: key facts

Definition: $transgenic animal = animal expressing an extra (foreign) gene$; Over 95% are mice.
Five uses: $physiology ∣ disease models ∣ biological products ∣ vaccine safety ∣ chemical safety$; Learn one example for each.
Rosie the cow (1997): $human α -lactalbumin; 2.4 g per litre of milk$; Nutritionally more balanced for human babies.
Biological product example: $α -1-antitrypsin \to emphysema$; Attempts also for PKU and cystic fibrosis.
Regulation in India: $GE A C = Genetic Engineering Approval Committee$; Decides validity of GM research and safety of releasing GMOs.

How to answer Transgenic Animals questions

Most questions ask for uses with examples, or apply a use to a case. Classify the case into one of the five uses.

1Define a transgenic animal in one line (expresses an extra, foreign gene); add that over 95% are mice.
2Identify the purpose in the question: understanding a gene, modelling a disease, making a product, testing a vaccine or a chemical.
3Give the NCERT example for that purpose (insulin-like growth factor; cancer/cystic fibrosis/rheumatoid arthritis/Alzheimer's; α-1-antitrypsin, Rosie; polio vaccine; toxicity testing).
4Explain the advantage: cheaper products, faster safety results, fewer monkeys used, models for testing treatments.
5For Rosie, give year, protein and amount (1997, human α-lactalbumin, 2.4 g/L).
6For ethics, mention unpredictable effects and the role of GEAC.

Transgenic Animals in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Transgenic animals as producers of biological products

Suppose a dairy research station has a transgenic cow that, like Rosie, makes 2.4 g of human alpha-lactalbumin per litre of milk and gives 15 litres of milk a day.

How much alpha-lactalbumin does the cow produce in a day and in a 300-day lactation? Why is this approach attractive compared with making the protein in other ways?

Try it first, then show the solutionSolution

Per day: 2.4 g/L × 15 L = 36 g.
Per lactation: 36 g × 300 = 10,800 g = 10.8 kg.
Biological products are often expensive to make; a transgenic animal secretes the protein in milk, from which it can be collected regularly, and the milk itself is more balanced for human babies.

Answer: 36 g per day; 10.8 kg in 300 days; cheaper, continuous production of a human protein in milk.

Memory hook: A transgenic cow is a living protein factory.

Tricks to remember Transgenic Animals

Short memory aids. Say each one aloud once, then use it on a question the same day.

Five uses: P-D-B-V-C
Physiology, Disease, Biological products, Vaccine safety, Chemical safety: 'Please Don't Bring Very Cold milk'.
Use it when: Listing uses.
Rosie 97, 2.4
Rosie was born in '97 and gave 2.4 g/L.
Use it when: Rosie facts.
Mice are the majority
95 out of 100 transgenic animals squeak.
Use it when: Over 95% are mice.

Transgenic Animals: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Definition · 1 mark · Very short answerBoard level

What are transgenic animals? Which animal makes up most of them?

Try it first, then show the solutionSolution

Animals whose DNA has been manipulated to possess and express an extra (foreign) gene; over 95% of them are mice.

Answer: Animals expressing a foreign gene; mostly mice (over 95%).

Example 2: Rosie · 2 marks · Very short answerBoard level

Name the first transgenic cow. What was special about its milk?

Try it first, then show the solutionSolution

Rosie (1997) (1 mark).
Its milk contained human alpha-lactalbumin (2.4 g per litre), making it nutritionally more balanced for human babies than natural cow milk (1 mark).

Answer: Rosie; human α-lactalbumin-enriched milk (2.4 g/L).

Example 3: Five uses · 5 marks · Long answerHarder board level

Explain any five uses of transgenic animals with an example of each.

Try it first, then show the solutionSolution

Normal physiology and development: studying gene regulation, e.g. insulin-like growth factor (1 mark).
Study of disease: models for human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's (1 mark).
Biological products: α-1-antitrypsin for emphysema; Rosie's α-lactalbumin-rich milk (1 mark).
Vaccine safety: transgenic mice test polio vaccine safety, possibly replacing monkeys (1 mark).
Chemical safety: animals made more sensitive to toxins give toxicity results in less time (1 mark).

Answer: Physiology, disease models, biological products, vaccine safety, chemical safety, with examples as above.

Example 4: Disease models · 2 marks · Very short answerHarder board level

How do transgenic animals help in finding new treatments for human diseases? Give two diseases for which models exist.

Try it first, then show the solutionSolution

Transgenic animals carrying disease-related genes develop the disease, so they act as models in which new treatments can be tested and gene contributions understood (1 mark).
Models exist for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's (any two) (1 mark).

Answer: They mimic human disease for testing treatments; e.g. cancer, Alzheimer's.

Example 5: Faster toxicity results · 2 marks · Very short answerHarder board level

Explain why transgenic animals give results of chemical toxicity testing in less time than normal animals.

Try it first, then show the solutionSolution

They carry genes that make them more sensitive to toxic substances than non-transgenic animals (1 mark).
So harmful effects appear at lower doses and sooner, shortening the time needed to judge safety (1 mark).

Answer: Greater sensitivity to toxins shows effects sooner.

Example 6: Replacing monkeys · 3 marks · Short answerHOTS / competency

Suppose a vaccine company wants to stop using monkeys to test each batch of polio vaccine. Explain how transgenic mice could help, what must first be proved, and one ethical benefit.

Try it first, then show the solutionSolution

Transgenic mice are being developed to test vaccine safety (e.g. polio vaccine) before use in humans (1 mark).
First, experiments must prove the mouse test is successful and reliable, giving the same safety judgement as the monkey test (1 mark).
Ethical benefit: fewer primates are used in testing; mice are easier to breed and maintain (1 mark).

Answer: Transgenic mice can test batches if proven reliable, reducing the use of monkeys.

Where students lose marks in Transgenic Animals

The slips examiners see most often, and what to write instead.

Mistake: Defining transgenic as 'cloned'
Cloning and transgenesis are confused.
Wrong working
Transgenic animals are genetically identical copies of an animal.
Right working
Transgenic animals carry and express an extra (foreign) gene.
Do this: Trans-gene = gene from across (another source).
Usually costs: 1 mark.
Mistake: Wrong protein for Rosie
Biological products are mixed.
Wrong working
Rosie produced α-1-antitrypsin.
Right working
Rosie produced human alpha-lactalbumin (2.4 g/L).
Do this: Lactalbumin is a milk protein: Rosie the cow.
Usually costs: 1 mark.
Mistake: Uses listed without examples
Students write headings only.
Wrong working
Uses: study of disease, biological products.
Right working
Study of disease (models for cancer, Alzheimer's); biological products (α-1-antitrypsin).
Do this: One example per use.
Usually costs: ½ mark per use.
Mistake: Saying most transgenic animals are cows
Rosie is memorable.
Wrong working
Most transgenic animals are cows and sheep.
Right working
Over 95% are mice.
Do this: Mice are the majority.
Usually costs: 1 mark.

Exam tips

For 5-mark questions, give all five uses with one example each.
Quote Rosie's details exactly: 1997, human α-lactalbumin, 2.4 g per litre.
Link vaccine testing to polio and the possible replacement of monkeys.
Mention GEAC when ethics or safety of GMOs is asked.
Keep answers to NCERT examples; avoid naming unrelated products.

Practice questions on Transgenic Animals

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Transgenic animals that carry genes making them more sensitive to toxic substances than normal animals are used for:
(a) vaccine safety testing (b) chemical safety testing (c) producing α-1-antitrypsin (d) studying insulin-like growth factor
Hint
Results in less time.
Answer
(b) chemical safety testing (toxicity testing).
Q2 · 1 mark · Very short answerBoard level
Which human protein produced by transgenic animals is used to treat emphysema?
Hint
An anti-protease.
Answer
α-1-antitrypsin.
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Transgenic mice may replace monkeys in testing the safety of polio vaccine.
Reason (R): Transgenic mice are being developed to test the safety of vaccines before they are used on humans.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
If reliable.
Answer
(a).
Q4 · 2 marks · Very short answerHOTS / competency
Suppose a lab introduces into mice a gene from another species that increases production of insulin-like growth factor, and the mice grow much larger than normal. What use of transgenic animals does this illustrate, and what can be learnt?
Hint
Normal physiology and development.
Answer
It illustrates the study of normal physiology and development: altering the formation of insulin-like growth factor and observing the effect (larger size) reveals the factor's biological role in growth and how its gene is regulated.
Q5 · 4 marks · Case-basedHarder board level
Read and answer.
Suppose a news item says: 'A company has produced transgenic goats whose milk contains a human protein for a lung disease, and plans to release GM fish into a river to boost fish catches.'
(a) Name the human protein likely to be used for the lung disease and the disease. (1)
(b) Which category of use of transgenic animals does the goat example show? (1)
(c) Why would releasing GM fish need approval, and from which Indian body? (2)
Hint
GEAC.
Answer
(a) α-1-antitrypsin, for emphysema. (b) Production of biological products. (c) GM organisms introduced into ecosystems can have unpredictable effects (on native species, food webs, gene flow), so their safety must be assessed; in India, approval comes from the Genetic Engineering Approval Committee (GEAC).
Q6 · 2 marks · Very short answerHarder board level
Give two reasons why biological products made by transgenic animals are valuable, and name one disease for which such attempts are being made besides emphysema.
Hint
Cost; human protein.
Answer
Biological products are often expensive to make by other means, and transgenic animals can produce human proteins continuously (e.g. in milk) for collection. Attempts are being made for phenylketonuria (PKU) and cystic fibrosis.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What percentage of transgenic animals are mice?Show answer
Over 95 per cent.
2.In which year was Rosie produced?Show answer
1997.
3.Which vaccine's safety is tested in transgenic mice?Show answer
Polio vaccine.
4.Name two diseases with transgenic animal models.Show answer
Cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's (any two).
5.Which growth factor is studied using transgenic animals?Show answer
Insulin-like growth factor.
6.Expand GEAC.Show answer
Genetic Engineering Approval Committee.

Transgenic Animals: frequently asked questions

What are transgenic animals?

Animals whose DNA has been manipulated so they possess and express an extra (foreign) gene; over 95% are mice.

What are the uses of transgenic animals?

Studying normal physiology and development, modelling human diseases, producing biological products, testing vaccine safety and testing chemical safety.

What was special about Rosie the cow?

Rosie (1997) was the first transgenic cow; her milk contained human alpha-lactalbumin (2.4 g/L), making it more balanced for human babies.

How do transgenic animals help vaccine testing?

Transgenic mice are being used to test the safety of vaccines such as polio vaccine and could replace monkeys if proved reliable.

Who regulates GM organisms in India?

The Genetic Engineering Approval Committee (GEAC), which decides on the validity of GM research and the safety of releasing GMOs.