GM Microbes

Pregunta	Respuesta
Extra Reading - Malaria	Recently reseachers have been able to develop an entire chemical pathway into yeast to enable it to make Artemisinic - a natural antimalarial drug found in the plant Sweet Wormwood. Very good as it will provide fast production of the drug. But many third world countries grow this plan on farms - will synthetic production put them out of jobs and money? Also will the Biotech company make a profit as 3rd world countries can't afford to buy them at profitable prices & malaria is not an issue in developing world.
Problems	Human genes contain INTRONS but bacteria/prokaryotic hosts' DNA doesn't and so they can't deal with them. To overcome this, use mRNA where the introns have already been processed out. This is copied in to DNA (cDNA) and then this is placed in the host for copying. This allows human genes to be genetically modified in prokaryotic hosts.
Prokaryotic Host Problems - PTM	Lots of human proteins undergo 'post-translational modification' to become active. Many bacteria can't carry out PTM - PTM processes include glycosylation, phosphorylation, acetylation etc.
Prokaryotic Host Advantages	Bacteria are rapid growers, grow in cheap conditions and are easy and cheap to supply They are great hosts but have their limitations
Eukaryotic Host Problems	Expensive and require more complex and pricey conditions. They are slow growers and hold more ethical issues. They can get infected easily rendering them useless & a waste of lots of money.
Eukaryotic Host Advantages	Very good at PTM & can remove introns automatically via RNA splicing
Risk of GM Escaping in to the Environment Prevention - Biological Containment	Biological Containment: The strains are genetically disable so they are produced to rely exclusively on conditions supplied by the medium on which they are grown - if they escape they will die or be unable to reproduce and spread. 'The outside is lethal'. For example, they are modified so they are unable to produce essential amino acids themselves and so it is supplied in their medium - away from it they die. OR they can be made recombinant deficient to prevent transfer of new genes to the outside world. This minimises the risk of genetic exchange as they can't undergo recombination during DNA replication.
Risk of GM Escaping in to the Environment Prevention - Physical Containment	Physical Containment: The very minimum is just the application of good microbiological practice. E.g. the use of air hoods, sterilisation and negative pressure air systems. Good in theory but always the risk of error.
Risk of GM Escape	Robert Holiday calculated the risk of GM escape at every stage of each process. E.g. he worked out the probability of ingesting something GM, then the probability of it bypassing the stomach acid, then the probability of genetic exchange etc. He said it was a total chance of 10^-0... VERY UNLIKELY In the 40 years of GM technology, there have been no links of any controversy being exclusively linked to GM. GM has been blamed but never exclusively linked. E.g. Smallpox escaped from a lab - not GM. & The great potato scandal - was GM but didn't escape.
Insulin!	- Now routinely produced in microbes & used to treat type 1 diabetes. - Originally animal insulin (cow/pig) was used to treat it. Porcine insulin is very similar genetically to human insulin and can be genetically modified to be identical. Straight porcine insulin was used by most due to it being cheap & easy to acquire. Risks included being contaminated by viruses and prions (BSE) but there was no alternative - it was take the risk or die! It could also cause rare adverse immune reactions - which is when modified porcine insulin was used.
GM Human Innsulin	First clones in E. Coli in 1980. It required PTM, the removal of C-chain & the insertion of sulphur-sulphur cross links which was carried out by chemical processing of proinsulin. It was carried out in yeast as these can carry out PTM - but yields are lower. Both methods are used commercially. It went in to commercial use very fast. After 2 years it was in clinical trials and after 4 years was in wide use. VERY FAST.
Was GM Human Insulin introduced Too Hastily?	Very rarely things go from discovery to use within 8 years - VERY FAST. But a lucky escape. GM insulin was introduced in the same year as the BSE epidemic in the UK. Bovine spongy encephalitis or mad cow disease spread rapidly in the early 90s. The BSE prions have been found in human tissues such as tonsils showing that it could have occurred in the pancreas. The BSE prions are the likely cause of human CJD and had we continued to use bovine insulin for longer, we may have had a CJD epidemic... Lucky Escape!
Making GM Human Insulin in Bacteria	Insulin is normally synthesised in pancreatic islet cells and consists of 2 chains linked by sulphur brides from cystein residues. These bridges must be in the correct place for the protein to be active. The genomic sequence contains introns so the preproinsulin mRNA is used and copied in to cDNA instead. the proproinsulin cDNA is split in to the A & B chains and separately they are fused on to the beta-galactose gene and inserted in to separate plasmids. The 2 plasmids are then introduced to E. coli and induced with IPTG to activate the beta-galactocidase gene to gain a fusion protein. The Beta-gal gene is then purified out to leave the 2 pure chains. These are then mixed together under the correct conditions to join them together with the formation of 3 s-s bridges. Product is then cleaned to make sure its correct and safe for human prescription
GM Human Growth Hormone	It is now routinely produced from E. coli. But is it ethical? should it be given to boost congenital dwarves? It's a very unpleasant process and given to young children - do they really have a choice? It can be used to boost vitality and mobility in elderly people - going against nature? Also used to improve athlete performance - unfair and cheating?
GM Bovine GH & Milk - Arguments FOR	- Can boost milk yields by 20% in Dairy Cattle (Banned in Uk but used widely in US) - Cheap & widely available - No PTM required - 20% yield increase means 20% fewer cows for the same yield, so you save on food, space, and methane contamination - Been used for 15 years and no health scare yet...
GM Bovine GH & Milk - Arguments FOR	- Increased mastitis & ulcers at injections sites which leads to animal suffering and higher vet bills - Milk contains higher levels of growth promoter hormone (IGF-1). This is identical to human IGF-1 and can be absorbed in the gut, but is there a potential risk? - We don't need the milk. So the additional money and animal suffering is unnecessary.
Should it be Published?	The H5N1 virus is easily modifiable. 1 modification allows the virus to be transmitted in ferrets by coughing. The authors wanted to publish the method, but it was halted initially due to biosecurity fears. Does GM provide scope for bioweapons? In the end the work was published.
Main GM Microbes Points	- Deontological argument again is the unnaturalness of the processes. - Utilitarian argument again is the risks carried with GM; safety of humans and ecological risks and bioweaponry - But GM drugs are purer and safer and screened more rigorously than other sources - so perhaps risk is lower (utilitarian argument FOR)? - There have been no reported GM accidents in 40 years but stuff isn't usually labelled as GM so maybe that's why the media doesn't report on GM concerns - Justice issues as the main pro is affordability - why should we patent microbes for our economic gain?
Terminology	In the 70's when it first came out, in the USA it was termed 'genetic engineering', but Brits called it 'Genetic manipulation'. Immediate bad connotations. More recently the term 'genetic modification' has been used.
What is GM?	1. human interference with natural genomes. 2. Introducing new genes or changing them by inserting/deleting DNA. 3. Selective breeding on a whole new level - this is a very passive/non-invasive form of GM. 4. The new technology is allowing the crossing of species barriers.
First Pioneered?	First pioneered in bacteria and viruses, then later moved to yeast and then to plants. Animals was much trickier but got there eventually. Can now do it in somatic tissues of humans, to try and cure or alleviate genetic disease. Can't manipulate human genes or germ cells due to the fear of them passing uncontrollably through generations
Human GM?	Only permitted in somatic tissues and not germ cells. GM precision tends to decrease as the complexity of the organism increases. You can get high precision and efficiency in bacteria but not in animals. If you're careful you can achieve precision in animals, but the efficiency is lost - very high failure rate!
Ethical Rationales	These are ALL utilitarian: 1. Commercial production of medicinal drugs. 2. Improving crops & livestock rapidly - faster growth/disease/pest resistance/higher yield/better nutrition etc. 3. Investigation in to how genes work & what does what in what organisms. 4. To create animal models of human genetic diseases for research or drug purposes. 5. Gene therapy to correct genetic defects - currently only allowed in only in somatic tissues. Majority of GM is carried out on crops or microbes for industrial/economical purposes.
Main Objections	Unnatural crossing of species barriers! 'Breaches natural spp barriers and violates the natural integrity of spp.' 'The teleos of animals can be so drastically modifies so as to alter the direction of evolution' FOX, 1990 Quite unlikely but get where he's coming from...
Response to Fox, 1990	Evidently not a biologist as he uses the example of inserting ELEPHANT growth hormone in to CATTLE... Silly boy. It's unlikely that it will alter the direction of evolution. But.. final statement 'teleos should be respected and the gene pool should be worthy of moral consideration' - this is true. We are turning nature 'un-natural' & do we really have the right to do this?
Genomic Identity	Should it be an aspect of an organism's value? We are interfering with 100s of years of natural evolution for our own limited gain and are these gains worthy of the violation on nature? Do the gains benefit the bioshpere as a whole or just humans?
Arguments for GM	Almost exclusively Utilitarian. GM benefits more than it detriments.
Arguments against GM	Deonotological - It is inherently wrong and we shouldn't be doing it. It is unnatural. Utilitarian - There is a risk to humans so we shouldn't do it (safety)
History	Selective breeding = mild form of GM & been doing it since early days of agriculture. Didn't really know why it worked until Darwin's theory of Natural Selection. In the 1920's the idea of 'eugenics' was promoted - essentially the process of 'wiping out bad genes and the less fit'. But took a negative turn whin Hitler adopted it for the Holocaust. Prior to this, psych wards used to sterilise patients so they wouldn't pass on their 'bad' genes. Didn't understand how genes or traits were carried until Watson & Crick discovered DNA.
First GM Microbe!	Carried out on bacteria in USA in the 70's. A circular piece of bacterial DNA (plasmid) was taken & cut once with a restriction enzyme to leave a linear piece of DNA with sticky ends. Then genomic DNA or mRNA was cut from a higher organism with the same restriction enzymes so sticky ends were complimentary. The genomic DNA was inserted to the Circular DNA which was then sealed with DNA ligases. Left with a circular piece of DNA which has the new gene set incorporated with the original plasmid. This is known as recombinant DNA and acts as a vector. It is inserted back in to the bacteria & so can multiply rapidly.
Cloning of recombinant DNA	It is propogated by inserting the recombinant DNA (desired gene set incorporated into bacterial DNA plasmid) into a suitable bacterial host. This reproduces to multiply and replicate the plasmid. You end up with lots of copies of the new gene/DNA segment. N.B. This is GM NOT Cloning!

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	Creado por Alice Burke hace más de 11 años