Transgenic Animals

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.