Transgenic animals

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Transgenic animals

  1. 1. By, DAMARIS BENNY DANIEL II Msc. Zoology
  2. 2.  A transgenic animal is one that carries a foreign gene that has been deliberately inserted into its genome.  Transgenesis is the process by which mixing up of genes takes place.  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.
  3. 3.  First transgenic animal was a ‘Supermouse’ created by Ralph Brinster (U Pennsylvania) and Richard Palmiter (University of Washington) in 1982.  It was created by inserting a human growth hormone gene in mouse genome.  The offspring was much larger than the parents.  Mouse – common transgenic expt.  Other animals include pig, goat, cow, sheep, fish etc.
  4. 4.  Step 1 – Construction of a transgene ◦ Transgene made of 3 parts:  Pomoter  Gene to be expressed  Termination sequence  Step 2 – Introduction of foreign gene into the animal ◦ Pronuclear microinjection method ◦ Embryonic stem cell method.
  5. 5.  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 using a micropipette.  Eggs with the transgenes are kept overnight in an incubator to develop to a 2 cell stage.  The eggs are then implanted into the uterus of a pseudo - pregnant female (female which has been mated with a vasectimized male the previous night)
  6. 6.  Transgenic animals can be created by manipulating embryonic stem cells.  ES cells are obtained from the inner cell mass of a blastocyst.  Transgene is incorporated into the ES cell by ◦ Microinjection ◦ By a retro virus ◦ By electroporation  Transgenic stem cells are grown in vitro.  Then they are inserted into a blastocyst and implanted into a host’s uterus to grow normally.
  7. 7.  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 offsprings are mated to form homozygous strains.
  8. 8.  Multiple insertion – too much proteins  Insertion into an essential gene – lethality  Insertion into a gene leading to gene silencing  Insertion into a different area can affect the gene regulation
  9. 9.  Superfish ◦ Increased growth and size ◦ Growth hormone gene inserted into fertilized egg. ◦ Transgenic salmon grows about 10 – 11 times faster than normal fish.  Glo fish ◦ GM freshwater zebra fish (Danio rerio) ◦ Produce by integrating a fluorescent protein gene from jelly fish into embryo of fish.
  10. 10.  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.  Oncomouse ◦ Mouse model to study cancer ◦ Made by inserting activated oncogenes.  Smart mouse ◦ Biological model engineered to overexpress NR2B receptor in the synaptic pathway. ◦ This makes the mice learn faster like juveniles throughout their lives.
  11. 11.  Enviro pig ◦ Pigs have trouble fully digesting a compound known as phytate found in many cereal grains used to feed them. ◦ Transgenic pigs are created by introducing phytase gene of E.coli. ◦ Phytase enzyme is thus produced in the salvary 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.
  12. 12.  Bioreactors whose cells have been engineered to synthesis marketable proteins.  More economical than producing desired protein in cell culture.  Transgenic cattle ◦ Transgenic cows are made to produce proteins lactoferrin and interferons in their milk. ◦ Prion free cows resistant to mad cow disease.  Transgenic sheep ◦ For good quality wool production.  Transgenic goat ◦ Goats that could express tissue plasminogen activator, anti thrombin III, spider silk etc in milk.
  13. 13.  Alba, the EGFP (Enhanced Green Flurescent protein) bunny  Created in 2000 as a transgenic artwork.  ANDi was the first transgenic monkey, born in 2000.  “ANDi” stands for “inserted DNA” spelled backwards.  An engineered virus was used to insert the harmless gene for green fluorescence protein (GFP) into ANDi’s rhesus genome.  ANDi proves that transgenic primates can be created, and can express a foreign gene delivered into their genome.
  14. 14.  Medical importance ◦ Disease model ◦ Bioreactors for pharmaceuticals ◦ Xenotransplantation  Agricultural importance ◦ Disease resistant animals ◦ For improving quality and quantity of milk, meat, eggs and wool production  Industrial importance ◦ Toxicity sensitive transgenic animals to test chemicals. ◦ Spider silk in milk of goat
  15. 15.  Blurring the lines between species by creating transgenic combinations.  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.  Various bioethicist argue that it is wrong to create animals that would suffer as a result of genetic alteration.
  16. 16.  Transgenic goats engineered to produce human breast milk ( Journal Transgenic Research, August 2012) ◦ University of California scientists created the transgenic goats by transferring human genes for breast milk enzymes and proteins into goat embryos. ◦ Produce 60 percent of the lysozyme and lactoferrin found in human mother’s milk. ◦ For babies of mothers who aren’t present, or can’t nurse them, milk from these transgenic goats could provide the next-best alternative.  Bioluminescent transgenic mouse model for study mammary gland tumour development. (PLoS ONE, aug 2012) ◦ Research done by Cancer Biology and Therapeutics Group, Ireland
  17. 17.  Transgenic technology is a field that is under constant evolution.  Many transgenic animals have been successfully created for a variety of purposes, and the prospects are enormous.  It holds great potential in many fields including agriculture, medicine and industry.  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.
  18. 18.  Satyanarayana U, Biotechnology (2010), 1st edition, Books and allied (P) Ltd, Kolkata.  Channarayappa, Molecular Biotechnology – Principles and Practices (2006), 1st edition, University Press Pvt Ltd, Hyderabad.  Smith E John, Biotechnology (1996), 3rd edition, Cambridge University Press  http://dsc.discovery.com/technology/tech-10/genetic- engineering/10-transgenic-animals-03.html  www.biomedcentral.com/1471-2407/12/209  http://news.e-healthsource.com/index.php?p=news1&id=534197

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