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71 Cards in this Set
- Front
- Back
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Stimulus-response path for a coordinated response: |
1) Stimulus detected by receptor in sense organ. 2) Electrical impulse along a sensory neurone to the brain. 3) This acts as the coordinator and decides the response. 4) Electrical impuse along a motor neurone to the effector which can be a muscle or a gland that carries out the appropriate response. |
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Stimulus-response path for a reflex action: |
1) Harmful stimulus detected by receptor 2) Electrical impulse along a sensory neurone to the spinal cord, which acts as the cooordinator 3) Electrical imoulse in relay / intermediate neurone 4) Electrical impulse in motor neurone to the effector, which carries out the response |
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Taxes: |
1) Simple response determined by the direction of the stimulus 2) Mobile organism responds to environmental change 3) Moves towards a favourable stimulus (positive taxis) 4) Moves away from an unfavourable stimulus (negative taxis) |
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Kineses: |
1) A form of response in which an organism does not move towards or away from a stimulus 2) The more unpleasant the stimulus, the more rapidly it moves or changes direction 3) Purpose to return organism to the more favourable environment 4) Increase in random movements 5) Important when stimulus is less directional e.g. temperature or humidity |
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Tropism: |
1) A growth movement of part of the plant in response to a directional stimulus 2) Can be positive or negative 3) Phototropism; Geotropism; Hydrotropism |
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Autonomic Nervous System control of heart rate: |
1) Involuntary and unconscious 2) Sympathetic stimulates effectors so speeds up activity - fight or flight 3) Centre in the medulla oblongata increases heart rate, linked to SAN by sympathetic nervous system 4) Parasympathetic generally inhibits effectors, slowing activity and conserving energy 5) Centre in the medulla oblongata decreases heart rate, linked to SAN by parasympathetic nervous system |
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Role of chemoreceptors in control of heart rate: |
1) Increased muscular / metabolic activity 2) More CO2 produced by respiring tissues 3) Blood pH lowered 4) Chemoreceptors in carotid artery increase frequency of impulses in medulla oblongata 5) Centre in medulla oblongata increases frequency of impulses to SAN via sympathetic nervous system 6) SAN increases heart rate 7) Increased blood flow removes CO2 faster 8) CO2 level returns to normal |
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Role of pressure receptors in control of heart rate: |
1) Located within walls of carotid arteries 2) When blood pressure higher than normal they transmit nervous impulses to centre in medulla oblongata that decreases heart rate 3) Impulse via parasympathetic nervous system to SAN causing heart rate to drop 4) When blood pressure lower than normal they transmit nervous impulses to centre in medulla oblongata that increases heart rate 5) Impulses via sympathetic nervous system to SAN causing heart rate to increase |
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Structure of the Pacinian corpuscle: |
1) Responds to mechanical stimuli - pressure 2) Occur deep in the skin and in ligaments/joints 3) Has a single sensory neurone at the centre of layers of tissue surrounded by a gel 4) This has a special type of sodium channel in its plasma membrane called the stretch-mediated sodium channel 5) Permeability to sodium changes when the shape changes |
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Function of the Pacinian corpuscle: |
1) In normal, resting state the stretch-mediated sodium channels are too narrow to allow sodium to pass - resting potential 2) When pressure is applied it changes shape and the membrane becomes stretched 3) This opens the sodium channels and sodium ions diffuse in 4) This depolarises the membrane and produces a generator potential 5) This then creates an action potential that passes to the CNS |
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Rod cell structure and function: |
1) Can't distinguish different wavelengths - black and white images 2) More of them 3) Spatial summation occurs - many rod cells synapse with a single bipolar neurone 4) Therefore more likely that stimulus reaches threshold value 5) Allow us a higher degree of visual sensitivity 6) Hard to distinguish between separate sources of light (low visual acuity) |
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Cone cell structure and function: |
1) 3 different types each with own wavelength of light 2) Different pigment requires a higher light intensity to break it down 3) Only light of high intensity will create a generator potential 4) Each connect to a single bipolar neurone 5) Give good visual acuity, but low sensitivity |
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Hormonal System: |
1) Communication by chemicals (hormones) 2) Transmission in the bloodstream 3) Transmission fairly slow, travels to all parts of the body 4) Response is slow and widespread 5) Response is often long lasting 5) Effect may be permanent and irreversible |
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Nervous System: |
1) Communication by nerve impulses 2) Transmission by neurones 3) Transmission is very rapid 4) Nerve impulses travel to specific parts of the body 5) Response is localised, rapid and short lived 6) Effect is temporary and reversible |
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Tropisms controlled by IAA: |
1) Cells at the tip of the shoot produce IAA which it transported down the shoot 2) Initially it is transported to all sides 3) Light causes it to migrate to shady side 4) IAA causes cell elongation so cells on shady side elongate more 5) The shaded side grows faster causing the shoot to bend towards the light (positive phototropism) 6) In geotropism, the high concentration of IAA causes root tissue to not elongate (opposite effect in roots) |
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Structure and function of a neurone: |
1) Cell body contains nucleus and lots of rough ER for the production of proteins and neurotransmitters 2) Dendrons subdivide into dendrites that carry nerve impulses to the cell body 3) The axon carries the nerve impulses away from the cell body 4) Schwann cells provide electrical insulation and carry out phagocytosis 5) The myelin sheath increases the speed of transmission 6) Nodes of Ranvier are gaps between adjacent Schwann cells where there is no myelin 7) Depolarisation occurs at nodes of Ranvier (saltatory conduction) |
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Maintenance of a resting potential across an axon: |
1) Resting potential makes the inside of the axon negative relative to the outside 2) (3) Sodium ions are actively transported out by sodium potassium pumps, and (2) potassium actively transported into the axon 3) This creates a chemical gradient and the sodium ions begin to diffuse naturally into the axon and potassium diffuse out 4) Potassium gates are mainly open, but sodium gates mainly closed - axon membrane more permeable to potassium 5) There is also an electrical gradient as ions are charged 6) Equilibrium is established - no net movement of ions |
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Sequence of events that causes an action potential: |
1) If a stimulus exceeds the threshold value sodium channels open 2) Sodium diffuses in and reverses the charge across the membrane - depolarisation 3) Sodium channels close and potassium channels open 4) Potassium moves out along electro-chemical gradient - repolarisation 5) Hyperpolarisation - potassium channels slow to close, so slight overshoot 6) Resting potential - ion channels reset |
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Factors that affect the speed at which an action potential travels: |
1) Myelin sheath - saltatory conduction and increases speed of transmission 2) Axon diameter - greater diameter = faster due to less leakage of ions 3) Temperature - affects rate of diffusion so higher temp = faster nerve impulses |
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Refractory Period: |
1) It is the time during which it is impossible to generate further action potentials 2) Ensures action potential is unidirectional 3) Produces discrete impulses 4) Limits the number of action potentials |
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Spatial Summation: |
1) Number of presynaptic neurones synapse with single postsynaptic neurone 2) Collectively they release enough neurotransmitter to overcome threshold value 3) They can therefore collectively trigger a new action potential |
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Temporal Summation: |
1) Single presynaptic neurone releases neurotransmitter many times over a short period 2) The total amount of neurotransmitter exceeds the threshold value triggering a new action potential |
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Cholinergic Synapse: |
1) Arrival of action potential at presynaptic neurone causes calcium channels to open 2) Calcium ions diffuse in, causing vesicles to move and fuse with presynaptic membrane 3) Vesicles release acetylcholine which diffuses across synapse and binds to complimentary receptors on postsynaptic membrane, causing sodium channels to open 4) Sodium diffuses in an generates a new action potential 5) Enzyme breaks down acetylcholine and it is recycled |
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Agonist Drugs on Synaptic Transmission: |
Agonists stimulate the nervous system by creating more action potentials in the postsynaptic neurone: 1) Mimic a neurotransmitter (same shape) 2) Stimulate the release of more neurotransmitter 3) Inhibit the enzyme that breaks down the neurotransmitter |
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Antagonist Drugs on Synaptic Transmission: |
Antagonists inhibit the nervous system by creating fewer action potentials in the postsynaptic neurone: 2) Block receptors on the sodium/potassium ion channels on the postsynaptic membrane |
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Structure of a Sarcomere: |
1) I bands - light bands which have no overlap between actin and myosin, just actin 2) A bands - dark bands which have overlap between actin and myosin 3) H-zone may or may not have overlap depending on state of contraction 4) Z-line - found at the centre of each I band (the distance between the Z lines make up a sarcomere) |
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Change of sarcomere during muscle contraction: |
1) During contraction the sarcomere shortens (i.e. the Z lines move closer together) 2) I band becomes narrower 3) H-zone becomes narrower 4) A band remains the same width |
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Slow Twitch Fibres: |
1) Contract more slowly and with less power over a longer period 2) Adapted for endurance work 3) Adapted for aerobic respiration to prevent build up of lactic acid 4) Have a large store of myoglobin and glycogen, lots of mitochondria and a rich blood supply |
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Fast Twitch Fibres: |
1) Contract more rapidly but provide powerful contractions for a short period of time 2) Adapted for intense exercise 3) Adapted by having thicker and more numerous myosin filaments 4) A higher concentration of enzymes involved in anaerobic respiration 5) A store of phosphocreatine, which can rapidly generate ATP from ADP in anaerobic conditions |
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Muscle Contraction: |
1) The arrival of the action potential at the neuromuscular junction causes calcium channels to open 2) Calcium diffuses into the sarcoplasm and causes tropomyosin to move so that myosin heads can form a cross-bridge with the actin 3) An ATP attaches to each myosin head causing it to detach from the actin 4) ATPase hydrolyses ATP and head returns to its original position 5) The myosin head then reattaches further along the actin filament 6) Known as the sliding filament theory |
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Energy for Muscle Contraction with and without oxygen: |
1) Hydrolysis of ATP supplies energy needed for movement of the myosin head 2) In anaerobic conditions ATP is generated using phosphocreatine 3) It is stored in muscles and acts as a reserve supply of phosphate to combine with ADP 4) The phosphocreatine store is replenished using phosphate from ATP when the muscle is relaxed |
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Self-Regulating control system: |
1) The set point (desired level or norm at which the system operates) is monitored by receptors that detect deviation away from set points and alert the controller, which coordinates the information and sends instructions to an appropriate effector, which brings about the changes needed to return system to set point creating a feedback loop, which informs the receptor of the changes to the system. |
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Physiological responses to a rise in core body temperature and how it is detected: |
1) Detected by thermoreceptors in heat loss centre in hypothalamus which detect a rise in the temperature of passing blood. 2) Vasodilation - arterioles widening - heat lost by radiation 4) Lowering of body hair - no air to insulate |
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Physiological responses to a fall in core body temperature and how it is detected: |
1) Detected by thermoreceptors in heat gain centre in hypothalamus which detect a fall in the temperature of passing blood. Also located in skin. 2) Shivering - muscle contraction produces metabolic heat 3) Piloerection - hairs trap air for insulation 4) Increased metabolic rate 5) Decrease sweat production 6) Vasoconstriction - less heat loss by radiation |
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Ectotherms and how they regulate body temperature: |
1) Ectotherms are animals that use environment to regulate their body temperature 2) Expose themselves to the sun - SA 3) Shelter when too hot or burrow 4) Gain warmth from the ground 5) Generate metabolic heat 6) Colour variation to absorb or reflect |
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Second Messenger model of hormone action: |
1) Hormones produced by glands and secreted into the blood. Carried in the blood plasma to target cells with complementary receptors on the cell membrane - hormone-receptor complex which activates an enzyme inside the cell, resulting in the production of a chemical that acts as a second messenger 2) Second messenger causes a series of chemical changes that produce the required response |
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Falling of blood glucose levels and physiological response: |
1) Drop in blood glucose caused by insufficient dietary carbohydrate intake or excessive exercise 2) Detected by alpha cells in islets of Langerhans 3) Secrete glucagon which binds to receptors on liver cells 4) Activates an enzyme that converts glycogen to glucose - glygcogenolysis 5) Increases the conversion of amino acids and glycerol into glucose - gluconeogenesis |
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Rising of blood glucose levels and physiological response: |
1) Due to absorbing glucose after meal 2) Detected by beta cells in islets of Langerhans 3) Secrete insulin that bind to recetor sites on almost all cells, causing a change in tertiary structure of the glucose transport channels, causing them to change shape and open so more glucose is taken up by the cells 4) Activation of enzymes that convert glucose to glycogen (glycogenesis) and fat |
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Type 1 Diabetes and how it is controlled: |
1) Known as insulin dependent as body doesn't produce any. Usually early onset. 2) May be result of autoimmune respose where body attacks own cells (beta cells) 3) Controlled by insulin injections 2-4 times a day 4) Monitored using biosensors 5) Carbohydrate intake and exercise must be controlled |
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Type 2 Diabetes and how it is controlled: |
1) Insulin independent - cells glycoprotein receptors have lost responsiveness 2) Typically late onset but increasinly earlier due to obesity and poor health 3) Controlled by regulating carbohydrate intake 4) Drugs may be given to slow the rate at which the body absorbs glucose from the intestine |
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How hormones control the Menstrual Cycle: |
1) Begins when the uterus lining is shed 2) Pituitary gland releases FSH into blood which stimulates follicles in the ovary to grow and mature. 3) Growing follicles secrete oestrogen. Low level of oestrogen causes the uterus lining to build up, and inhibits FSH and LH (negative feedback) 4) As the follicle grows, more oestrogen is produced, critical point causes release of more FSH and LH (positive feedback) 5) Surge in FSH and LH production causes ovulation. 6) Empty follicle develops into the corpus luteum which produces progesterone 7) Progesterone maintains uterus lining thickness and inhibits release of FSH and LH 8) If egg not fertilised the corpus luteum degenerates and so progesterone level falls, causing uterus lining to breakdown. 9) FSH no longer inhibited, cycle starts again |
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Main features of the genetic code: |
1) Amino acid coded for by base triplet 2) Code is degenerate 3) Stop codons 4) Code is non-overlapping 5) Code is universal |
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mRNA structure: |
1) Pentose sugar is ribose 2) Uracil replaces Thymine 3) Single stranded, single helix molecule 4) Quantity varies from cell to cell depending on metabolic activity 5) Shorter - just the length of a gene |
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Transcription in Protein Synthesis: |
1) Formation of pre-mRNA 2) DNA Helicase acts on specific region of DNA breaking hydrogen bonds between complementary bases 3) Two strands separate exposing nucleotide bases in that region 4) RNA polymerase moves along the template causing complementary nucleotides to align 5) As the RNA polymerase moves along the DNA strand rejoins behind it |
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Splicing in Protein Synthesis: |
1) Non-coding introns are removed and the functioning exons fuse together 2) Exons can join in a number of different combinations 3) Splicing occurs in the nucleus so the mRNA is now small enough to pass out the nuclear pore |
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Translation in Protein Synthesis: |
1) Ribosome attaches to the starting codon at one end of the mRNA 2) tRNA with complementary anticodon sequence moves to the ribosome and pairs up with the sequence on the mRNA. tRNA carries a specific amino acid. 3) Ribosome moves along the mRNA, and by means of an enzyme and ATP, the two amino acids are joined by peptide bond 4) Synthesis continues until a stop codon is reached |
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Mutations on Protein Structure: |
1) A mutation is a change in a gene / base sequence / structure of DNA 2) Happens spontaneously, but increased by mutagenic agents e.g. ionising radiation 3) Nonsense mutation - codon is now stop codon 4) Mis-sense mutation - different amino acid coded for 5) Silent mutation - degenerate, no change 6) Addition/Deletion - frame shift |
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Proto-oncogenes: |
1) Stimulate cell division 2) In a normal cell, growth factors attach to a receptor protein on the cell-surface membrane and switch on genes necessary for DNA replication 3) Gene mutation can cause them to become oncogenes, permanently switching genes on leading to excessive cell division 4) Cell divides too rapidly and tumour or cancer develops |
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Tumour Suppressor Genes: |
1) Inhibit cell division, preventing tumour formation 2) If it mutates, it will become inactive 3) Mutant cells formed are normally structurally and functionally different to normal cells 4) Most of them die but any that survive clone and form tumours 5) These may be harmless (benign) or harmful (malignant) |
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Totipotency: |
1) A totipotent cell can develop into any body cell 2) Found in embryos up to the 32 day stage 3) They later differentiate and become specialised 4) Embryonic stem cells can be grown in vitro and then induced to develop into a range of different tissues e.g. skin grafts, blood cells 5) Ethical issues, but can get stem cells from adult bone marrow |
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Oestrogen on Gene Transcription: |
1) Transcription factors stimulate a gene to undergo transcription 2) Oestrogen easily diffuses into cell membranes, and combines in the cytoplasm with a site on a receptor molecule of the transcription factor (complimentary shapes) 3) Receptor molecule shape changes, releasing the inhibitor molecule from the DNA binding site on the transcriptional factor 4) Transcriptional factor can now enter the nuclear pore and combine with DNA to stimulate transcription of the gene |
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siRNA on Gene Expression: |
1) Small interfering RNA 2) Prevents gene expression by breaking down mRNA before translation occurs 3) An enzyme cuts large, double stranded molecules of RNA into siRNA 4) One of the two strands of siRNA combines with an enzyme 5) The siRNA guides the enzyme to the mRNA by pairing its bases with the complementary ones on the mRNA 6) Enzyme then cuts the mRNA into smaller sections so it can't be translated |
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Making a protein using gene technology: |
1) Isolation of the DNA fragments that have the gene for the desired protein 2) Insertion of the DNA fragment into a vector 3) Transformation - transfer DNA into suitable host 4) Identification of host cells that have successfully taken up the gene by gene markers 5) Growth/cloning of the population of host cells |
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Gene Isolation using Reverse Transcriptase: |
1) A cell that readily produces the protein is selected 2) These cells have large quantities of the relevant mRNA which can be extracted 3) Reverse transcriptase is then used to make DNA from RNA. This DNA is known as cDNA 4) To make the other strand of DNA, DNA polymerase is used to build up complimentary nucleotides on the cDNA 5) The resulting double strand of DNA is the gene |
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Gene Isolation using Restriction Endonucleases: |
1) These are enzymes that cut DNA at a specific recognition sequence 2) Sometimes it cuts between two opposite bases leaving blunt ends 3) Others cut in a staggered fashion leaving sticky ends |
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Replica Plating - Bacteria taking up new DNA: |
1) As well as inserting desired gene, 2 marker genes are inserted 2) Resistance gene to antibiotic ampicillin left in tact 3) Desired gene inserted within gene for tetracycline resistance 4) Host bacteria cells mixed with plasmid vector 5) Small sample transferred to agar plate containing ampicillin 6) Colonies allowed to develop, and the ones that grow are resistant to ampicillin 7) Replica plate is made with tetracycline 8) Repeated and ones that die are the ones that incorporated the desired gene 9) Can also use flourescence |
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Polymerase Chain Reaction (PCR): |
1) PCR in DNA replication in vitro 2) Separation of the DNA strand 3) DNA fragments, primers and DNA polymerase placed in thermocycler 4) Heated to 95'C to break hydrogen bonds between the complementary bases 5) Cooled to 55'C to allow primers to join to their complementary bases 6) Synthesis of DNA at 72'C - optimal temperature for DNA polymerase 7) Cycle takes 2 minutes and doubles amount |
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Differences between PCR and in vivo DNA replication: |
1) PCR in vitro; DNA replication in vivo 2) PCR uses heat to break hydrogen bonds, DNA replication uses DNA helicase 3) PCR uses primers |
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Benefits of Genetic Modification: |
1) Increased yield from animals/crops 2) improving the nutrient conent of food 3) Introducing resistance to disease or pests 4) Making crop plants tolerate herbicides 5) Tolerance to extreme environments 6) Making vaccines 7) Producing medicines for treating disease |
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Anti-thrombin production in genetically modified goats: |
1) Sperm from male goat used to fertilise mature eggs from female goat in vitro 2) Human gene for anti-thrombin inserted alongside gene for milk protein 3) Kids with anti-thrombin gene crossbred 4) Anti-thrombin extracted from milk and purified |
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Germ-Line Therapy: |
1) Involves replacing or supplementing the defective gene in the fertilised egg 2) Ensures that all cells in the organism will develop normally 3) Offers more permanent solution 4) Moral and ethical issues mean it is currently prohibited |
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Somatic-Cell Therapy: |
1) Targets just the affected tissues so the additional gene is not present in sperm or egg 2) Treatment needs to be repeated as cells are continually dying 3) Treatment at present has limited success |
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Liposomes on Cystic Fibrosis (Gene Therapy): |
1) Functioning CFTR genes inserted into bacterial plasmid vectors 2) These are cloned and wrapped in a lipid molecule to form a liposome 3) These are sprayed into the nostrils as an aerosol and they pass through the phospholipid bilay entering epithelial cells where gene is expressed 4) Liposome aerosol may not be fine enough to pass through, and even if successful, very few are expressed |
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Adenoviruses on Cystic Fibrosis (Gene Therapy): |
1) Adenoviruses made harmless by interfering with a gene involved in their replication 2) Viruses grown in epithelial cells in the lab along with plasmids that have normal CFTR gene inserted 3) CFTR gene becomes incorporated into DNA of the adenovirus 4) Adenoviruses isolated and purified and introduced to patients nostrils 5) Adenoviruses inject DNA into epithelial cells 6) However, may cause infections, or patients may develop immunity to them |
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Gene Therapy on SCID: |
1) Normal ADA gene isolated using restriction endonucleases 2) ADA gene inserted into retrovirus which is grown with host cells in a lab to increase their number 3) Retrovirus mixed with patients T cells 4) Retrovirus inject a copy of the normal ADA gene into the T cells 5) T cells provide genetic code needed to make ADA |
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Gene Therapy effectiveness, risks and benefits: |
1) Short-lived effect (except germ-line) 2) Can induce an immune response 3) Genes not always expressed 4) Not effective in treating multi-gene conditions 5) Moral and ethical issues - Eugenics? 6) Expensive |
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DNA Sequencing: |
1) Set up four test tubes each containing: - A primer to start DNA synthesis that is labelled (fluorescently or radioactively) - DNA polymerase 2) When the terminator nucleotide binds (random) synthesis stops 3) Lots of fragments all different sizes produced. Can be separated using gel electrophoresis |
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Gel Electrophoresis: |
1) Fragments loaded into wells on agarose gel plate 2) Electric current separates fragments due to size (smaller go further faster) 3) DNA is negatively charged so moves to the +ve electrode 4) Lane with DNA fragments of known size can be run so size of fragment can be estimated |
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Restriction Mapping |
1) Determines the pattern of fragments in a gene sequence 2) Cut with restriction enzyme A (digest) - run gel to detect number of fragments formed 3) Do same with another restriction enzyme B and run in gel 4) Cut the sequence with both A and B again run in gel 5) From fragment lengths in separate and combined digests you can work out the sequence of where the cuts were made in the whole gene sequence and hence the order of the fragments 6) Incomplete digest may give total length that appears longer than original 7) Processes now automated using fluorescent labelled terminator nucleotides and computer analyses |
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Genetic Screening: |
1) Used to determine if an unborn child might be affected by a genetic disorder 2) The order of nucleotides on the mutated gene is determined by DNA sequencing 3) Fragment of DNA with complimentary bases to mutated portion of the gene is produced 4) DNA probe is formed by radioactively labelling the DNA fragment 5) PCR produces multiple copies of the probe 6) Probe added to single-stranded DNA from person being screened 7) If donor has mutated gene, probe will bind 8) These DNA fragments can be distinguished from the rest using x-ray film (will be exposed) |
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Genetic Fingerprinting: |
1) Extraction - DNA taken from sample 2) Digestion - Restriction endonucleases cut DNA into fragments 3) Separation - Fragments separated using gel electrophoresis 3.5) Fragments transferred to nylon membrane by southern blotting 4) Hybridisation - DNA probes added to label the fragments 5) Development - Membrane with radioactively labelled DNA fragment is placed onto x-ray film and reveals dark bands where probes have attached |
