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Transgenic animals

Presented by- Prachi Dixit

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Content Transgenesis .Introduction.Definition. History .Production of transgenic animals.The methodology.Examples of transgenics.Importance.Issue related to transgenic technology.Conclusion.

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Transgenesis Process of introducing foreign or exogenous DNA into an animals genome is called transgenesis.

Transgenesis is the process of introducing an exogenous gene called a transgene into a living organism so that the organism will exhibit a new property and transmit that property to its offspring.

Transgenesis can be facilitated by liposomes by liposomes, enzymes, plasmid vectors, viral vectors, pronuclear injection, protoplast fusion, and ballistic DNA injection.

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Introduction A transgenic animal is one that carries a foreign gene that has been deliberately inserted into its genome.

Foreign genes are inserted into the germ line of the animal , so it can be transmitted to the progeny.

Transgenic technology has led to the development of fishes, live stock and other animals with altered genetic profiles which are useful to mankind.

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Horse Donkey Mule

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Definition Transgenic animals are the genetically modified organisms which have a foreign gene in their genome due to which they show certain properties which are different from non- genetically modified organisms.

Glow fish as pets.Sheep with more wool. Cow producing more milk with lower cholesterol.

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Example & History

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Example – “Dolly” (sheep)

Dolly was a female domestic sheep, and the first mammal cloned from an adult somatic cell, using the process of nuclear transfer. Born5 July 1996

She was cloned by Sir Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute, part of the University of Edinburgh, Scotland.

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Example – “supermouse”

First transgenic animal was a “Supermouse” created by ‘Ralph Brinster’ and ‘Richard Palmiter’ In 1982.

It was created by inserting a human growth hormone gene in mouse genome.

The offspring was much larger than the parents.

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Example- “Herman” (Bull)

First transgenic mammal “Herman” ,the bull was the first genetically modified or transgenic mammal in the world.

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Production of transgenic animals

Transgenic technology has been developed and perfected in the laboratory mouse. Since the early1980’s hundreds of different genes have been introduced into various mouse strains. These studies have contributed to understanding of gene regulation

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The methodology Step 1- construction of a transgene. Transgene made of three parts-• Promoter• Gene to be expressed• Termination sequence

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Cont…

Step 2- Introduction of foreign gene into the animal.

Pronuclear microinjection method. Embryonic stem cell method. Retrovirus-mediated gene transfer method.

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Cont… Step 3 – Screening for transgenic positives.

Transgenic progenies are screened by PCR to examine the site of incorporation of the gene. Some transgenes may not be expressed if integrated into a transcriptionally inactive site.

Step 4 – Further animal breeding is done to obtain maximal expression.

Heterozygous offspring's homozygous strains are mated to form.

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Retro virus mediated gene transfer method

Retroviruses can be used for the transfer of foreign genes into animal genomes.This can best be done at 4-16 cell stage embryos.Completion of this process requires that the host cell undergoes the S phase of the cell cycle. Therefore, retroviruses effectively transduce only mitotically active cells. Very high rates of gene transfer are achieved with the use of retroviruses.

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Disadvantages Limitations on the size of the foreign DNA insert (usually 9 to 15 kb) transferred.

The genome of the retroviral strain can be integrated into the same nucleus as the transgene. This means that the virus itself could be produced by the transgenic organism and create a problem especially if the animal will be used for production of food. Low copy number integration.

Additional steps required to produce retroviruses.

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Microinjection method

A female animal is superovulated and eggs are collected.

The eggs are fertilized in vitro.

The transgene containing solution is Injected into the male pronucleus.

Eggs with the transgenes are kept overnight in an incubator to develop.

The eggs are then implanted into the uterus of a pseudo pregnant female.

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Cont…Because of the disadvantages of the retroviral vectors, microinjection of DNA is currently the preferred method for producing transgenic mice.

The mouse was the first animal to undergo successful gene transfer using DNA microinjection .

This method involves:- transfer of a desired gene constructed from another member in the same or different species into the pronucleus of a reproductive cell.

Then it will be cultured in vitro until reaches embryonic phase then transferred to the recipient cell.

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Embryonic stem cell method

Transgenic animals can be created by manipulating embryonic stem cell.

ES cells are obtained from the inner cell mass of the blastocyst.

Transgenic stem cells are grown in vitro.

Then they are inserted into a host uterus to grow normally.

Harvest the Inner Cell Mass (ICM) from 3 day old blastocysts.

Inject the transgenic ES cells into the blastocoele of a new 3-day old host blastocyst.

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Some example of transgenic animals

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Transgenic fishSuper fish•Growth hormone gene inserted into fertilized egg.•Increased growth and size.•Transgenic fish grows about 10-11 time faster than normal fish.

Glo fish •Genetically modified zebra fish.•Produced by integrating a fluorescent protein gene from jelly fish into embryo of fish.

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Super fish

Glo fish

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Transgenic mouseOnco mouse•Mouse model to study cancer.•Made by inserting activated oncogenes.

Alzheimer’s mouse•In the brain of Alzheimer’s patients, dead nerve cells are entangled in a protein called amyloid.•Mouse made by introducing amyloid precursor gene into fertilized egg of mice.

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Alzheimer’s mouse

Onco mouse

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Transgenic pigEnviro pig•Pigs have trouble fully digesting a compound known as phytate in many cereal grains used to feed them.•Transgenic pigs are created by introducing phytase gene of Ecoli.•Phytase enzyme is thus produced in the salivary gland of pig.•It degrades indigestible phytate with the release of phosphate that is readily digested by pigs.

Pig for organ transplant•Pigs with human genes, in order to decrease the chance of organ rejection by human body.

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Transgenic sheepFor good quality wool.

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Transgenic monkey“ANDI” was the first transgenic monkey, born in 2000.ANDI proves that transgenic primates can be created and can express a foreign gene delivered into their genome.

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Transgenic cow“ROSIE” was the first transgenic cow , born in 1997. Produced human protein enriched milk at 2.4g/lt contains human gene Alpha lactalbumin.

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Recent researchTransgenic goats engineered to produce human breast milk.•University of California scientists created the transgenic goats by transferring human genes for breast milk enzymes and proteins into goat embryos.

•Produce 60% of the lysozyme and lactoferrin found in human mother’s milk.

•For babies of mother’s who aren’t present or can’t nurse them, milk from these transgenic goats could provide the next best alternative.

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importanceIndustrial importance –•Toxicity sensitive transgenic animals to test chemicals.•Spider silk in milk of goat.

Medical importance –•Disease model.•Xenotransplantation.

Agriculture importance –•Disease resistant animals.•For improving quality & quantity of milk, meat, eggs & wool production.

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Application Production of organs for transplant.Surgical techniques.Cancer models.Antibody production.Study of role of gene.

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Issue related to transgenic technology

There may be health risks associated with transgenics.

There may be long term effects on the environment when transgenic animals are released into the field.

Abnormalities suffered are more.Reduced fertility.Respiratory and circulatory problems.Weak immune system.

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Conclusion With proper research and careful use the transgenic animals can go a long way in solving several problems for which science doesn't have a solution till now.

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Thank you