How Transgenic Animals Aid Disease Research and Vaccine Development
Animals that have modified genomes are called Transgenic Animals. A foreign gene is being inserted into the genome of the animal with the purpose to alter its DNA. To improve the genetic traits of the target animals, this method is used. Earlier, selective breeding methods were used for the improvement of these genetic traits. In this method, the animals were mated to produce an individual with improved genetic characteristics with the desired genetic traits. This time-consuming and expensive method was later replaced by recombinant DNA technology. These genes are passed on to successive generations. Transgenic animals are genetically modified and are therefore known as Genetically Modified Organisms. The first genetically modified organism was engineered in the year 1974 by Rudolph Jaenisch. He injected the SV40 virus in early mouse embryos and developed a transgenic mouse.
Methods for Creating Transgenic Animals
Following methods are used for creating the Transgenic Animals -
Physical Transfection
In this method, the gene of interest is directly injected into the pronucleus of a fertilized ovum. It is the very first method that proved to be effective in mammals. This method is applied to a wide variety of species. Other methods of physical transfection include particle bombardment, ultrasound, and electroporation.
Chemical Transfection
One of the chemical methods of gene transfection includes transformation. In this method, the target DNA is taken up in the presence of calcium phosphate. The DNA and calcium phosphate co-precipitates, which facilitates DNA uptake. The mammalian cells possess the ability to take up foreign DNA from the culture medium.
Retrovirus-Mediated Gene Transfer
To increase the chances of expression, the gene is transferred utilizing a vector. Since retroviruses can infect the host cell, they are used as vectors to transfect the gene of interest into the target genome.
Viral Vectors
Viruses are used to transfect rDNA into the animal cell. The virus can infect the host cell, express well, and replicate efficiently.
Bactofection
The gene of interest is transferred into the target gene with the help of bacteria with this process.
Examples of Transgenic Animals
Following are some of the examples of transgenic animals:
Transgenic Fish
Genetic transfer has been done in various fishes such as common carp, Atlantic salmon,etc. Transgenic salmon was the first genetically modified animal for food production.
Transgenic Chicken
D.W.Salter and L.B.Crittenden produced an avian leukosis virus resistant strain of the chicken in the year 1987.
Transgenic Rabbit
The first transgenic rabbit was successfully produced in 1985. They are used in the field of molecular farming.
Transgenic Cow
The name of the first transgenic cow is Rosie and it was developed in 1997. They are mainly developed with two objectives- increased milk production and molecular farming.
Transgenic Sheep
The first mammal to be produced from an adult cell was a sheep. The sheep’s name was Dolly. In this, the udder cells from a 6-year-old Finn Dorset white sheep were injected into an unfertilized egg from a Scottish Blackface ewe, which had its nucleus removed. Electrical pulses were used to fuse the cells. After the fusion of the nucleus of the cell with the egg, the resultant embryo was cultured for six to seven days. A transgenic sheep, Dolly was born by implantation into another Scottish Blackface ewe. Generally, transgenic sheeps are produced in order to achieve better meat production.
Transgenic Mice
Transgenic mice take birth when DNA is injected into the oocytes or one or two-celled embryos obtained from female mice after hormonal treatment. After injecting the DNA, the embryo is implanted into the uterus of receptive females.
Benefits Of Transgenic Animals
Some of the benefits of transgenic animals are -
Normal Physiology and Development
The growth factor is altered by introducing a foreign gene in transgenic animals. These animals facilitate the study of gene regulation and its effect on the everyday functions of the body.
Study of Diseases
These transgenic animals are specially designed to study the functions of genes in the development of certain diseases. Moreover, to take out a solution to disease, transgenic animals are used as model organisms. These transgenic models are used in research for the development of medicines. For example, we have transgenic models for diseases such as Alzheimer’s and cancer.
Biological Products
Transgenic animals are useful in obtaining biological products such as medicines and nutritional supplements. Some of the biological products such as medicines and nutritional supplements are produced and obtained from transgenic animals. Research for the manufacture of medicines to treat diseases such as phenylketonuria (PKU) and hereditary emphysema is going on. Rosie was the first transgenic cow in 1997 who produced milk that was rich in human protein. She produced about 2.4 grams per liter of milk. This milk contains the human gene alpha-lactalbumin and could be given to babies as an alternative to natural cow milk.
Vaccine Safety
For testing the safety of the vaccines, these transgenic animals are used as models before they are injected into humans. Mostly, this was done on Monkeys.
Conclusion:
Transgenic animals are close cousins to cloned animals with a slight technicality. It is interesting to read about technological advancement and evolution of species. Imagine if humans could be transgened for better outcomes. This article gives you a thorough understanding of modified genomes and their role in transgenic animals, methods of their creation, and popular examples. You can read it through to prepare better on the topic.
FAQs on Transgenic Animals: Meaning, Uses, and Importance
1. What exactly are transgenic animals as per the CBSE Class 12 syllabus?
Transgenic animals are organisms whose DNA has been manipulated to possess and express an extra, foreign gene. This is achieved using recombinant DNA technology. The primary purpose is to introduce a new trait, such as producing a specific protein, or to create models for studying human diseases and gene functions.
2. What are some key examples of transgenic animals and their specific purposes?
Several transgenic animals have been created for specific applications in medicine and research. Some notable examples include:
- Transgenic Mice: The most common models used to study how genes contribute to diseases like cancer and cystic fibrosis.
- 'Rosie' the Cow (1997): The first transgenic cow that produced human protein-enriched milk containing alpha-lactalbumin, making it nutritionally more balanced for human babies.
- Transgenic Fish: Created to grow larger and faster than their non-transgenic counterparts for aquaculture purposes.
- ANDi the Monkey (2000): The first transgenic primate, created by inserting a gene from a jellyfish to study gene expression.
3. What are the primary methods used to produce transgenic animals?
The creation of transgenic animals primarily involves a few key techniques. The most common methods are:
- Microinjection: In this method, the foreign DNA (transgene) is directly injected into the pronucleus of a fertilised ovum, which is then implanted into a surrogate mother.
- Retroviral Vector Method: A retrovirus is used as a vector to carry the desired gene and infect an early-stage embryo, integrating the foreign DNA into the host's genome.
4. What are the most important applications of transgenic animals in biology and medicine?
Transgenic animals are crucial for advancements in several fields. Their main applications include:
- Study of Normal Physiology: To understand how genes are regulated and affect normal body functions, such as the role of insulin-like growth factor.
- Study of Diseases: Serving as models for human diseases to investigate new treatments. For example, transgenic mice are used to study Alzheimer's.
- Biological Products: They can be used as bioreactors to produce useful biological products, like human alpha-1-antitrypsin to treat emphysema.
- Vaccine Safety Testing: Used to test the safety and efficacy of vaccines before they are used on humans, such as the polio vaccine.
- Chemical Safety Testing: To assess the toxicity or safety of drugs and other chemicals.
5. Which animal makes up over 95% of all existing transgenic animals and why?
Over 95% of all existing transgenic animals are mice. This is because their genetic, biological, and behavioural characteristics closely resemble those of humans. Furthermore, they are small, easy to handle, have a short lifespan, and reproduce quickly, making them ideal and cost-effective models for genetic research and disease studies.
6. How is a transgenic animal fundamentally different from a cloned animal, such as Dolly the sheep?
The distinction lies in the genetic modification process. Transgenesis involves introducing a foreign gene from a different species to create a new, modified trait that wasn't previously present. In contrast, cloning is the process of creating a genetically identical copy of an entire organism using its own DNA, without introducing any foreign genes. Therefore, Dolly the sheep was a clone of her parent, not a transgenic animal, as no new genes were added to her DNA.
7. Why is the topic of transgenic animals considered important for a Class 12 Biology student?
Studying transgenic animals is significant for a Class 12 student as it demonstrates a powerful real-world application of biotechnology. It connects theoretical concepts of genetics and molecular biology to practical solutions in medicine, agriculture, and industry. It also introduces students to the critical domains of bioethics and the regulations surrounding genetic modification, which are essential for any future biologist or informed citizen.
8. What are the major ethical issues associated with creating and using transgenic animals?
The creation of transgenic animals raises significant ethical concerns. Key issues include the potential for animal suffering caused by genetic modifications, the unknown long-term effects on the animals' health, and the risk of disrupting ecosystems if they escape into the wild. There is also a broader philosophical debate about the morality of altering an animal's genetic makeup for human benefit. To regulate this, organisations like the Genetic Engineering Approval Committee (GEAC) in India make decisions regarding the validity and safety of GM research.
