Question
What are transgenic animals? Describe the process of creating one. Give examples of transgenic animals and their applications. What was special about Rosie the cow?
(NEET + CBSE Board pattern)
Solution — Step by Step
A transgenic animal is one whose genome has been deliberately modified by introducing a foreign gene (transgene) from another organism. The transgene integrates into the animal’s DNA and can be expressed to produce a desired protein.
The basic process:
- Isolate the gene of interest
- Attach it to a suitable promoter (to ensure expression)
- Introduce the construct into a fertilised egg (by microinjection into the pronucleus)
- Implant the modified egg into a surrogate mother
- Screen the offspring for transgene expression
| Application | Example | Details |
|---|---|---|
| Pharmaceutical production | Rosie the cow | Produced human alpha-lactalbumin-enriched milk (2.4 g/L) — nutritionally balanced for human babies |
| Disease models | Transgenic mice with cancer genes | Used to study cancer progression and test drugs |
| Vaccine safety testing | Transgenic mice with human genes | Test vaccine immune response in human-like system |
| Gene therapy research | Mice with cystic fibrosis gene | Study gene correction strategies |
| Product safety testing | Transgenic animals with human-like toxin sensitivity | Replace traditional animal testing with more accurate models |
Rosie was the first transgenic cow, born in 1997. She carried the gene for human alpha-lactalbumin and produced milk enriched with this protein at 2.4 g/litre. This made the milk more nutritionally balanced for human infants — closer to human breast milk than normal cow milk.
The significance: demonstrating that farm animals could serve as living “bioreactors” — producing pharmaceutically or nutritionally valuable human proteins in their milk.
graph TD
A["Transgenic Animal Creation"] --> B["Isolate gene of interest"]
B --> C["Attach to promoter"]
C --> D["Microinject into fertilised egg"]
D --> E["Implant in surrogate"]
E --> F["Screen offspring"]
F --> G{"Applications"}
G --> G1["Pharma: Rosie - human protein in milk"]
G --> G2["Research: Disease model mice"]
G --> G3["Testing: Vaccine safety"]
style A fill:#fbbf24,stroke:#000,stroke-width:2px
style G1 fill:#86efac,stroke:#000Why This Works
Transgenic technology allows us to use animals as biological factories. The mammary gland is an ideal “production unit” because milk is easily collected without harming the animal, and mammary-specific promoters ensure the transgene is expressed only in milk (not in all tissues). This approach is called molecular farming or pharming.
The transgene integrates into the animal’s germline, meaning it can be passed to offspring — creating a self-sustaining production line of transgenic animals.
Common Mistake
Students often confuse transgenic animals with cloned animals. A transgenic animal has foreign DNA inserted (from a different species). A clone is a genetic copy of another individual of the SAME species. Dolly was a clone (no foreign DNA); Rosie was transgenic (human gene inserted). NEET tests this distinction directly.
For NEET, memorise these two names: Rosie = first transgenic cow (human alpha-lactalbumin), Dolly = first cloned mammal (SCNT from mammary cell). These two animals cover 90% of NEET biotechnology application questions.