Uses of genetic modificationGenetically modified crops – to grow in climates which are inhospitableTomatoes will not soften as easilyWheat resistant to herbicidesRice with added vitamin A
Genetically modified mice – mice can be genetically modified to develop humantypes of diseases such as Asthma and cancers which research scientists can thentest on to see which drugs workThese are coloured with GFP Green Jelly fish proteins used as genetic marker
Gene therapy - This is where scientists replace defective geneswith active genes cloned from healthy individuals.There are two types of gene therapy although this sort of therapy isin it’s infancy for humans.Germ line therapy – which is currently banned in most countriesthe more acceptableSomatic cell therapy which isn’t very successful however a youngman had his sight partially restored in 2008 using this method.
Tranformed Goats and Genetically modified sheep - Sheep and goats can have specificgenes for various proteins added alongside the milk promoter gene in a plasmid when stillzygotes.These proteins will be expressed in the mammary glands of the animals.The protein can then be extracted from the milk and used. Applications include: -Medicinalanti-thrombinanti-trypsin
The genes for spiders web proteins a very strong natural fibre can also be inserted intomammary gland of sheep and goats and will be expressed with the animals milk.Spiders can’t be farmed for their silk proteins as they are cannibals.But their silk can be used to create.Bullet-proof clothing as spider silk is tougher than KevlarWear-resistant lightweight clothingRopes, nets, seat belts, parachutesRust-free panels on motor vehicles or boatsBiodegradable bottlesBandages, surgical threadArtificial tendons or ligaments, supports for weak blood vesselshttp://www.biologymad.com/ [ accesssed 05/03/2012] Toole and Toole, 2008
So lets look at genetic modification of sheep so that they produce various proteins along with their milk. First of we’d need a plasmid.foreign genes can quite easily be incorporated into them using restriction enzymesand DNA ligase.
This plasmid contains a replicationorigin, several recognition sequencesfor different restriction enzymes (withnames like PstI and EcoRI), and twomarker genes, which confer resistanceto different antibiotics (ampicillin andtetracycline).Into this you could add the gene forGreen Fluorescent Jelly fish proteinalso.Then you’d add the gene for milkpromotion and designer gene which youwere adding to code for the particularprotein you wanted out of the milkIt could be a protein for inhalation tostop lungs destroying themselvesOr a protein to stop blood clottingOr it could be for spiders silk.
The sheep is given FSH hormones to increase ova maturation. These are harvested and fertilised in vitroThe ova are fertilised in the laboratory
A plasmid is prepared containing the designer gene the promoter sequence for b-lactoglobulin and agreen, fluorescent, jelly fish. Hundreds of copies of this plasmid are microinjected into the nucleus of the fertilised zygotes.Only a few of the zygotes will be transformed, but at this stage you can’t tell which.
The genes we introduce are coupled to a promoter for the milk protein β-lactoglubulin. Since this promoter is only activated in mammary gland cells, the inserted genes will only be expressed in mammary gland cells, and so will be secreted into thesheeps milk. This makes it very easy to harvest and purify without harming the sheep.
The zygotes divide in vitro until theembryos are at the 16-cell stage.
The 16-cell embryos are implanted into the uterus of surrogate mother ewes. Only a few implantations result in a successful pregnancy.Some of the lambs will be green this will determine which ones have been transformed and which lambs are unchanged. About 1 in 20 eggs are successful.
Collect milk from the transgenic sheep for the rest of their lives. Also breed from them in order to build up a herd of transgenic sheep.Purify the protein for example AAT, is worth about £50 000 per mg
The first transgenic sheep to produce AAT was called Tracy, and she was produced by PPL Pharmaceuticals in Edinburgh in 1993. :
Ethical and Moral ConsiderationsMany types of genetic engineering are considered to be socially unacceptable as itcan lead to Eugenics and potentially dangerous as man made genes added to theenvironment could drastically change the ecology of the country.For example a crop genetically engineered to withstand a certain herbicide whichwas going to increase the yield. May pass that gene to a weed. Then the weed wouldbecome resistant to the herbicide so the crop and the weed would then once morebe competing for nutrients and light.Then we’d have to come up with another type of herbicide which was compatiblewith the environment and the new crop we are growing. This would be a veryexpensive and take time to trial as we would have to be careful that we were notdamaging the environment.For these reasons GM Crops are banned in the UK
ReferencesToole and Toole AQA Biology Study Guide, Nelson Thornes. 2008Biology Mad Website Accessed March 1st 2012