Unit 5: Section 5- Drugs

A summary of the Drugs topic from edexcel's A2 Biology (Grey Matter)

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Drugs and Disease 1

  • Parkinson's disease affects motor skills (movement) as the neurones in the brain controlling movement are destroyed. These neurones normally produce dopamine (neurotransmitter), leading to a lack of dopamine
  • This causes a decrease in transmission of nerve impulses involved in movement, leading to symptoms such as tremors and slow movement
  • Depression is thought to be caused by a low level of the neurotransmitter serotonin. Serotonin transmits impulses across synapses in the areas of brain that control mood
  • L-dopa is a drug used to treat Parkinson's disease. It has a similar structure to dopamine, and is converted to dopamine by an enzyme in the brain when it is taken. This increases dopamine levels in the brain, increasing the mobility of the patient (dopamine not directly given as can't cross the blood-brain barrier)
  • MDMA (ecstasy) increases level of serotonin in the brain by inhibiting the reuptake of serotonin into the presynaptic neurone, and by triggering the release of serotonin from presynaptic neurones. Mean impulses are constantly triggered in the areas of brain which control mood, leading to mood elevation.
  • The Human Genome Project identified all the genes in the human genome, in order to identify genes and therefore proteins involved in disease
  • Information being used to create new drugs that target identified proteins
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Drugs and Disease 2

  • HGP has also highlighted common genetic variations between people, some of which can make drugs less effective. Drug companies use this to make new drugs that are effective in people with the variations
  • Moral and ethical issues
  • Drugs for specific genetic variations will increase research costs for drug companies, leading to more expensive drugs and potentially a two-tier health service (only available to the rich)
  • Some people may be refused an expensive drug as their genome means it won't be effective- may be the only drug available
  • Information held could be used by others eg, insurance companies to unfairly discriminate
  • Revealing that a drug may not work for a person may be psychologically damaging 
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Producing Drugs Using GMOs

  • Genetically Modified Organisms- Gene for target protein isolated using restriction enzyme, and copied using PCR. Copies inserted into plasmids and transferred into MOs. The modified MOs are grown so they produce the useful protein, which is purified and used as a drug. Eg. human insulin and human blood clotting factors.
  • Genetically Modified Plants- Gene for target protein inserted into bacterium, which infects a plant cell. Gene inserted into the plant cell DNA by the bacterium, and left to grow into an adult plant (every cell has a copy of the target gene). The protein can be purified from plant tissues or delivered by eating the plant. Eg. human insulin and cholera vaccine.
  • Genetically Modified Animals- Gene for target protein injected into the nucleus of a fertilised animal egg cell, which is implanted into an adult animal to grow into a whole animal. The target protein produced purified from the milk of the animal. Eg. human antithrombin from GM goats.
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