Examples Of Transgenic Animals

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Transgenic Animals

• Some important examples of transgenic animals are as follows

Transgenic Fish

• Gene transfers have been successful in various fish, such as common carp, rainbow trout, Atlantic salmon, catfish, goldfish, zebra - fish, etc.
• Transgenic Salmon
• Genetically modi fied salmon was the first transgenic animal for food production.
• The genetically modified sperms were fused with normal ova (eggs) of the same species.
• The zygotes which developed into embryos gave rise to much bigger adults than either parent.
• The transgenic salmon possesses an additional gene that codes for the growth hormone that allows the fish to grow larger more rapidly than the non - transgenic salmon.

Transgenic Chicken

• Avian leukosis virus ( ALV ) is a serious viral pathogen of chickens . D.W. Salter and L.B. Crittenden ( 1988 ) have produced an ALV - resistant strain of the chicken by introducing a defective genome of this virus into the genome of the chicken.
• This principle is also applied to evolve transgenic fish that can resist viral infections.

Transgenic Mice

• Mouse is the most preferred mammal for studies on gene tranfers due to its many favourable features like short oestrous cycle and gestation period, relatively short generation time, production of several offspring per pregnancy (i.e. , litter), convenient in vitro fertilization, successful culture of embryos in vitro, etc. As a result, the techniques for gene transfer and transgenic produc tion have been developed using mice as models in other animals.
• Recently, rats and rabbits are being used for research work on gene transfer.

Transgenic Rabbits

• Rabbits are quite promising for gene farming or the molecular farming, which aims at the production of recoverable quantities of pharmaceutically or biologically important proteins encoded by the transgenes.
• The following human genes encoding valuable proteins have been transferred into rabbits : interleukin 2, growth hormone, tissue plasminogen activator, alfa1 antitrypsin, etc.
• These genes were expressed in the mammary tissues and their proteins were harvested from milk.

Transgenic Goats

• Goats are being evaluated as bioreactors. Some human genes have been introduced in goats and their expression achieved in mammary tissues .
• The initial results are encouraging.

Transgenic Sheep

• Transgenic sheep have been produced to achieve better growth and meat production. For example, human genes for blood clotting factor IX and for alfa 1 antitryspin have been trans ferred in sheep and expressed in mammary tissue.
• This was achieved by fusing the genes with the mammary tissue - specific promoter of the bovine bita - lactoglobulin gene.
• Human growth hormone gene has also been introduced in sheep in order to promote growth and meat production.
• However, they also showed several undesirable effects like joint pathology, skeletal defects, gastric ulcers, infertility, etc.
• In 1990 Tracy, the transgenic ewe was bom in Scotland.

Transgenic Pigs

• The rate of transgenic production in pigs, sheep, cattle and goats is much lower (usually < 1 %) than that in mice (usually between 3-6 %) . The objectives in transgenic swine (pl. same, meaning pig), production are ( i ) increased growth and meat production and ( ii ) to serve as bioreactors.
• Transgenic pigs expressing human growth hormone do show improved growth and meat production, but they also show several health problems.
• In January 2002, an Edinburgh based therapeutics company announced the birth of a litter of transgenic pig clones.

Transgenic Cows

• The only successful transfection technique in cows is microinjection of fertilized ova, which may either be recovered surgically or may be obtained from ovaries extracted from slaughtered cows and cultured in vitro. The two chief objectives of transgenic production are as follows : ( i ) increased milk or meat production and ( ii ) molecular farming . Several human genes have been successfully transferred in cows and expressed the mammary tissue
• the protein is secreted in milk from where it is easily harvested.
• The name of first transgenic cow is Rosie.

Transgenic Dogs

• Dogie is a transgenic dog with excellent smelling power.
• It was used during attack on World Trade Centre (WTC) of the USA in 2001 to recover injured people from heaps of devastated building

ANDI

• DNA of a fluroescent jelly fish was introduced into an unfertilized egg of a Rhesus monkey in the test tube.
• The diploid egg underwent cleavage and the early embryo was implanted in a surrogate mother.
• ANDI, the first transgenic monkey was born on Oct 2. 2000.
• It has been named ANDI, the acronym of " inserted DNA "
• The credit for production of ANDI goes to Dr. Gerald Schatten of Oregon Health Sciences University, USA
• This work would be helpful for curing diseases such as breast cancer, Alzheimer's disease, diabetes and AIDS .

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