Drugs + Disease

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Parkinson's Disease

  • parkinson's disease is a brain disorder that affects motor skills
  • in parkinsons's, the neurones in parts of the brain that control movement are destroyed - these neurones normally produce the neurotransmitter dopamine, so losing them causes a lack of dopamine
  • this causes a decrease in the transmission of the nerve impulses involved in movement, leading to symptoms like tremors and slow movement
  • scientists know that the symptoms are caused by a lack of dopamine, they've developed drugs to increase the level of dopamine in the brain
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  • L-dopa is a drug used to treat the symptoms of Parkinson's disease
  • its structure is very similar to dopamine
  • when L-dopa is given, it's absorbed into the brain and converted into dopamine by the enzyme dopa-decarboxylase, which increases the level of dopamine in the brain
  • dopamine can't be used to treat Parkinson's disease because it can't enter the brain
  • a higher level of dopamine means that more nerve impulses are transmitted across synapses in parts of the brain that control movement
  • this gives sufferers of Parkinson's disease more control over their movement
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  • scientists know there is a link between a low level of the neurotransmitter serotonin and depression
  • serotonin transmits nerve impulses across synapses in parts of the brain that control mood
  • scientists have developed drugs (antidepressants) to increase the level of serotonin in the brain
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MDMA (ecstasy)

  • MDMA increases the levle of serotonin in the brain
  • serotonin is usually taken back into a presynaptic neurone after triggering an actional potential to be used again
  • MDMA increases the level of serotonin by inhibiting the uptake of serotonin into presynaptic neurones, and by triggering the release of serotonin from presynaptic neurones
  • this means that nerve impulses are contantly triggered in postsynaptic neurones in parts of the brain that control mood, so the effect of MDMA is mood elevation
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Human Genome Project

  • the HGP was a 13 year project that idnetified all of the genes found in human DNA - the information obtained is stored in databases
  • scientists use the databases to identify genes, and proteins, that are involved in disease - they are using this information to create new drugs that target the identified proteins
  • the HGP has also highlighted common genetic varitions between people
  • it's known that some of these variations make some drugs less effective
  • drug companies can use this knowledge to design new drugs that are effective in people with these variations
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  • creating drugs for specific genetic variations will increase research costs for drug companies - these new drugs will be more expensive, which could lead to a two-tier health service, where only wealthier people will be able to afford these new drugs
  • some people might be refused an expensive drug because their genetic make-up indicates that it won't be that effective for them (but it may be the only drug avaialable)
  • the information held within a person's genome could be used by others e.g. employers or insurance companies, to unfairly discriminate against them
  • revealing that a drug might now work for a person could be psychologically damaging to them
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Genetically Modified Microorganisms

  • the gene for the protein (drug) is isolated using restriction enzymes
  • the gene is copied using PCR
  • copies are inserted into plasmids (small circular molecules of DNA) which are transferred into microorganisms
  • the modified microorganisms are frown in large containers so that that divide and produce lots of the useful protein from the inserted gene
  • the protein can then be purified and used as a drug

lots of drugs are produced from genetically modified bacteria e.g. human insulin (used to treat type 1 diabetes) and human blood clotting factors (used to treat haemophilia)

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Genetically Modified Plants

  • the for the protein (drug) is inserted into a bacterium, which infects a plant cell
  • the bacterium inserts the gene into the plant cell DNA - the plant cell is now genetically modified
  • the plant cell is grown into an adult plant - the whole plant contains a copy of the gene in every cell
  • the protein produced from the gene can be purified from the plant tissues, or the protein (drug) could be delivered by eating the plant

some drugs have been produced from genetically modified plants e.g. human insulin and a cholera vaccine

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Genetically Modified Animals

  • the gene for the protein (drug) is injected into the nucleus of a fertilised animal egg cell
  • the egg cell is the implanted into an animal - it grows into a whole animal that contains a copy of the gene in every cell
  • the protein produced from the gene is normally purified from the milk of the animal

various animals have been modified with human genes to produce drugs e.g. human anithrombin (used to treat people with a blood clotting disorder) has been produced from genetically modified goats

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Benefits of GMOs

  • agricultural crops can be modified so they give a higher yield or are more nutritious, meaning plants can be used to reduce the risk of famine and malntrition
  • crops can also be modified to have pest resistance, so fewer pesticides are needed - this reduces costs (making food cheaper) and reduces any environmental problems associated with using pesticides
  • industrial processes often use enzymes, which can be produced from genetically modified organisms in large quantities for less money, which reduces costs
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Benefits of GMOs

  • some disorders can be treated with human proteins from GMOs instead of animal proteins - human proteins are safer and more effective
  • vaccines produced in plant tissue doesn't need to be refrigerated - this could make vaccines available to more people e.g. in areas where refrigeration (usually needed for strong vaccines) isn't available
  • producing drugs using plants and animals would be very cheap because once they are genetically modified, they can be reproduced using conventional farming methods, which could make some drugs more affordable for more people, especially those in poor countries
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Risks of GMOs

  • some people are concerned about the transmission of genetic material e.g. if herbicide resistant crops interbreed with wild plants, it could create 'superweeds' that are resistant to herbicides, and if drug crops interbredd with other crops people might end up eating drugs they don't need, which could be harmful
  • some people are worried about the long-term impacts of using GMOs - there may be unforseen circumstances
  • some people think it's wrong to genetically modify animals purely for human benefit
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