Extended response qu Flashcards

Question

HIV replication in cells

Answer 1

Attachment proteins attach to receptors on helper T cell/lymphocyte Nucleic acid/RNA enters the cell Reverse transcriptase converts RNA to DNA This inserted into host cell DNA Viral proteins/capsid/enzymes are produced Virus particles are assembled and released from the cell by ‘budding off’

Answer 2

Wipe down surfaces with antibacterial cleaner both before and after the experiment Use a bunsen burner in the work space so the convection currents draw microbes away from the culture Flame the inoculating loop before using it to transfer bacteria Flame the neck of any bottles before using and again before replacing the lid to prevent bacteria entering the vessel Keep all vessels containing bacteria open for the minimum amount of time Close all windows and doors to limit air currents

Answer 3

Large lipid droplets emulsified by bile salts Lipase hydrolyses triglycerides to monoglycerides/fatty acids Micelles contain bile salts and fatty acids/monoglycerides They make fatty acids/monoglycerides more soluble in water They bring fatty acids/monoglycerides to the lining of the ileum Fatty acids/monoglycerides are absorbed by diffusion They recombine at the smooth endoplasmic reticulum to form triglycerides Triglycerides transported in vesicle to golgi apparatus to associate with proteins and cholesterol to form chylomicrons Move out of epithelial cells by exocytosis and enter lacteals to go to the bloodstream

Answer 4

Salivary amylase in the mouth hydrolyses glycosidic bond in starch to disaccharide maltose Pancreatic amylase in the small intestine hydrolyses glycosidic bond in starch to disaccharide maltose Membrane bound disaccharidase maltase in the epithelium of the small intestine hydrolyses maltose to glucose Membrane bound disaccharidase sucrase in the epithelium of the small intestine hydrolyses sucrose to glucose and fructose Membrane bound disaccharidase lactase in the epithelium of the small intestine hydrolyses lactose to glucose and galactose

Answer 5

Proteases hydrolyse peptide bonds Endopeptidases in the stomach and small intestine act in the middle of polypeptide chains and break them up to increase the number of ends Exopeptidases in the small intestine act at the ends of polypeptides and produce dipeptides/amino acids Membrane bound dipeptidases in the epithelium of the small intestine hydrolyse the bond between dipeptides and produce amino acids

Answer 6

Positive cooperativity Hard for first oxygen molecule to bind After the first one binds, the tertiary structure of the haemoglobin is changed and it is opened so it is easier for the second and third oxygens to bind In the lungs there is a high pp oxygen, haemoglobin has a high affinity for oxygen so it loads more readily In respiring tissue there is low pp oxygen, haemoglobin has a low affinity for oxygen so it unloads more readily

Answer 7

The higher the rate of respiration The more carbon dioxide produced by tissues The lower the pH The greater the tertiary structure change of haemoglobin The more readily oxygen is unloaded The more oxygen available for respiration

Answer 8

Atrial systole - heart is full of blood and ventricles are relaxed, atria contract, higher pressure in atria than ventricles so atrioventricular valves open and blood flows into ventricles Ventricular systole - ventricle walls contract, pressure in ventricles higher than in atria so atrioventricular walls shut Ventricular systole - pressure in the ventricles higher than in the arteries so semilunar valves open and blood flows into arteries Diastole - ventricles relax, pressure in the ventricles is lower than in the arteries so semilunar valves shut Diastole - blood from the vena cava and pulmonary veins enters the atria and the cycle starts again

Answer 9

Arteries have thick walls made of collagen and smooth muscle to withstand high pressures Arteries have thick walls made of elastic fibres which can expand and recoil to maintain blood pressure Arteries have a narrow lumen to maintain high blood pressure Arteries have smooth walls to reduce friction Veins have large lumens to accommodate large amount of blood at lower pressure Veins contain valves that prevent the backflow of blood Arterioles have muscle cells to contract and narrow the lumen to limit blood flow to particular areas Capillaries have a small diameter allowing them to keep blood at low volumes and pressures Capillaries branch between cells so they can provide short diffusion distance Capillary walls are 1 cell thick for short diffusion distance The cells in the capillary walls have pores which allow blood plasma to leak out

Answer 10

Left ventricle contracts which means the hydrostatic pressure of the blood in the capillary is higher than the hydrostatic pressure of the tissue fluid Water and small soluble molecules are forced out the pores of the capillary Large proteins are too big to pass through so remain inside

Answer 11

Water potential of blood is lower than the tissue fluid due to the loss of water and the large proteins left in the capillary Water moves by osmosis back into the capillary down water potential gradient Lymphatic system collects excess tissue fluid, forming lymph The returns to the bloodstream via ducts to the vena cava

Answer 12

Water evaporates out stomata in the leaves/stalk Water potential gradient creates tension and pulls up water Adhesion to walls of xylem maintains tension Cohesion due to hydrogen bonding between water molecules maintains continuous column of water

Answer 13

At source cells, solutes like sucrose are actively loaded into sieve tube elements from companion cells. This decreases the water potential in sieve tube elements. Water then enters the sieve tube elements from the xylem and companion cells by osmosis, down a water potential gradient. This increases the hydrostatic pressure in the sieve tube elements at the source. At the sink, solutes are actively unloaded from the sieve tube elements. This increases the water potential in sieve tube elements at the sink. Water leaves the phloem and returns to the xylem by osmosis, decreasing the hydrostatic pressure at the sink. This creates a hydrostatic pressure gradient, pushing solutes from the source to areas of lower pressure at the sink.

Answer 14

Can use aphids which stick their mouthpieces into the phloem to drink the sap This shows presence of sugars When the aphid body is removed from the head, sap continues to flow This shows there is pressure in the phloem When a ring of bark and phloem is peeled from a section of tree trunk, the trunk swells above the removed section The liquid in the swelling contains sugar, proving the phloem is responsible for the transport of sugars Radioactively labelled carbon can be assimilated into plants to create sugars in photosynthesis This can be seen in thin slices of stems on x-ray film, showing that the phloem contains the sugars

Answer 15

Gills made up of stacked filaments which water runs over Filaments have lamellae which increase surface area Countercurrent exchange Blood and water flow in opposite directions More oxygenated blood comes across higher oxygenated water so oxygen movement is from water to blood Less oxygenated blood comes across oxygen depleted (but still higher conc.) water so oxygen movement is from water to blood Oxygen always moves from water to blood

Answer 16

Tracheoles have thin walls so short diffusion distance to cells Highly branched tracheoles so short diffusion distance and large surface area for gas exchange Tracheae provide tubes full of air so faster diffusion into tissues Fluid in the end of tracheoles moves into tissues during exercise so more air pulled in Muscle contraction forces air in/out spiracles and in/out tracheae

Answer 17

Air moves down trachea Which branches into 2 bronchus Which branch into bronchioles With branch into air filled sacs called alveoli Oxygen moves across the 1 cell thick alveolar epithelium into the 1 cell thick epithelium of the capillary Vice versa for carbon dioxide

Answer 18

External intercostal muscles contract Internal intercostal muscles relax Ribs move up and out Diaphragm contracts and flattens Thorax pressure decreases Pulmonary pressure less than atmospheric so air enters lungs

Answer 19

External intercostal muscles relax Internal intercostal muscles contract Ribs move down and in Diaphragm relaxes and moves up Thorax pressure increases Pulmonary pressure more than atmospheric so air leaves lungs

Answer 20

Pores called stomata which can be opened/closed by guard cells and let air in/out No cell is far from a stoma Many interconnecting air spaces in the mesophyll so gases readily come in contact with mesophyll cells Large surface area of mesophyll cells for rapid diffusion

Answer 21

Thick waxy cuticle Rolling of leaves to cover stomata and traps water vapour so no water potential gradient Hairy leaves trap still, moist air so no water potential gradient Stomata are in pits/grooves to trap still, moist air so no water potential gradient Reduced surface area to volume ratio of leaves e.g. pines

Answer 22

Small surface area to volume ratio to minimise area over which water is lost Waterproof coverings - chitin exoskeleton and waterproof cuticle Spiracles can be closed to reduce water loss

Answer 23

DNA unwinds Hydrogen bonds between DNA bases broken by DNA helicase Non-coding DNA strand acts as a template Free RNA nucleotides align by complementary base pairing and hydrogen bonding Adenine and uracil, cytosine and guanine RNA polymerase joins adjacent RNA nucleotides to form phosphodiester bonds through condensation reaction Pre-mRNA is spliced/introns are removed to form mRNA mRNA leaves the nucleus via nuclear pore

Answer 24

mRNA enters the cytoplasm and attaches to a ribosome Ribosome moves to the start codon tRNA molecule with a specific amino acid depending on the anticodon binds to the mRNA via hydrogen bonding between complementary base pairs of mRNA and the anticodon The ribosome moves along the mRNA to the next codon and a second tRNA molecule attaches (ribosome has 2 tRNA binding sites) Peptide bond forms between adjacent amino acids using energy from the hydrolysis of ATP Ribosome moves along mRNA until stop codon is reached This causes the polypeptide to be released from the ribosome

Answer 25

DNA is a double stranded polynucleotide chain, mRNA and tRNA are single stranded DNA has a double helix structure, mRNA is single helix, and tRNA is clover shaped DNA is the largest, then mRNA, then tRNA The pentose sugar for DNA is deoxyribose, for mRNA and tRNA it’s ribose DNA nitrogenous bases are ATCG, mRNA and tRNA bases are AUCG DNA is found in the nucleus, mRNA is found throughout the cell, tRNA is found in the cytoplasm All somatic cells have the same quantity of DNA, but varying levels of mRNA and tRNA depending on metabolic activity DNA is most stable, then tRNA, then mRNA (has no complementary base pairing)

Answer 26

Genetic material duplicates Homologous chromosomes pair up and form bivalents Equal lengths of chromatid are exchanged between non sister chromatids at the chiasmata They recombine and there is a new combination of alleles Homologous chromosomes line up randomly and cell divides Daughter cells receive a random combination of maternal and paternal chromosomes Independent segregation occurs and again and cells divide again 4 genetically different daughter cells

Answer 27

Random mutation leads to creation of new alleles Some mutations have advantageous effects due to selection pressure Individuals with the advantageous characteristic are more likely to survive and have reproductive success The allele is more likely to be passed on to the next generation Frequency of advantageous allele increases

Answer 28

Carbon dioxide reacts with ribulose bisphosphate, a 5C molecule To form two molecules of glycerine-3-phosphate, a 3C molecule This is catalysed by the enzyme rubisco GP is reduced to triose phosphate Using energy from ATP and by accepting H from reduced NADP One molecule of carbon from triose phosphate leaves the cycle each turn to be converted into organic substances The rest of the molecule is used to regenerate RuBP Energy is released from the hydrolysis of ATP

Answer 29

Light energy is absorbed by chlorophyll and splits water into protons and electrons The light energy absorbed by chlorophyll excites electrons They move up an energy level to leave the chlorophyll Electrons move along a series of electron carrier proteins embedded in the thylakoid membrane in a series of redox reactions As they move they release energy and this is used to pump protons across the chloroplast membranes This creates an electrochemical gradient so protons pass back across the membrane through ATP synthase down a concentration gradient This results in the production of ATP The protons combine with NADP to become NADPH

Answer 30

Similarities Both have electrons pass along a series of electron carrier proteins in a membrane Both times electrons lose energy as they move which is used to pump protons across the membrane Both times, an electrochemical gradient is created which cause protons to move back across the membrane through ATP synthase, which synthesises ATP Differences Protons and electrons in photophosphorylation (pp) come from photolysis of water, in oxidative phosphorylation (op) they come from NADH and FADH The membrane in pp is the thylakoid membrane, in op it is the inner mitochondrial membrane In pp, 18 molecules of ATP are generated, in op this is 30-32 molecules In pp, the protons combine with NADP to form NADPH, in op, protons and electrons combine with oxygen to form water

Answer 31

Glucose has 2 phosphate groups added from 2 molecules of ATP Phosphorylation makes the glucose molecule unstable and it splits into 2 3C compounds, triose phosphate The 2 triose phosphate molecules are oxidised by the removal of H to form 2 pyruvate molecules The H is picked up by 2 NAD molecules to give 2 NADH This process releases 4 ATP so the net amount of ATP produced is 2

Answer 32

NADH and pyruvate from glycolysis are actively transported into the mitochondrial matrix The pyruvate is oxidised to acetate and NAD picks up the H from this to form NADH Acetate combines with coenzyme A to form acetyl CoA Acetyl CoA reacts with a 4C molecule which releases coenzyme A and produces a 6C molecule that enters the Krebs cycle The 6C molecule loses 2CO2 ATP is synthesised from ADP and Pi, FAD is reduced to FADH and 3 NAD are reduced to NADH The cycle turns twice per molecule of glucose

Answer 33

NADH and FADH release protons and electrons The electrons are passed down a series of electron carrier proteins embedded in the inner mitochondrial membrane The energy lost as the electrons move is used to pump protons from the mitochondrial matrix into the intermembrane space This creates an electrochemical gradient so the protons move back across the membrane via ATP synthase, which synthesises ATP Oxygen acts as the final electron acceptor, combining with electrons and protons to form water

Answer 34

Plants and microbes Occurs in the cytoplasm of the cell Pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide Animals Occurs in the cytoplasm of the cell Pyruvate produced in glycolysis gains H from NADH which produces lactate and oxidises NAD so it can be reused in glycolysis

Answer 35

Nitrogen fixing bacteria break the bond in N2 in the atmosphere and fix this nitrogen into ammonium ions These bacteria are either free living in the soil or living on the root nodules of plants The ammonium ions in the soil are converted to nitrite then nitrate by nitrifying bacteria in a 2 stage oxidation reaction Nitrates are assimilated into plants Anaerobic denitrifying bacteria return nitrogen compounds back into nitrogen gas in the atmosphere Proteins, urea, and DNA are decomposed in dead matter and waste by saprobionts, which digest waste extracellularly, and return ammonium ions to the soil

Answer 36

Water soluble fertilisers are washed into rivers/ponds Nitrogen fertilisers stimulate excessive growth of algae which creates a blanket on the surface This blocks out light so plants below can’t photosynthesise and die Bacteria feed and respire on dead plant matter which results in an increase in bacteria This uses up the oxygen in the water so fish and other aquatic organisms die from lack of oxygen

Answer 37

Saprobionts, primarily bacteria and fungi, release enzymes onto dead organic matter These enzymes hydrolyse complex molecules like proteins, carbohydrates, and lipids Smaller, soluble molecules produced by extracellular digestion are then absorbed and can be used for respiration or stored for later use Products of decomposition like ammonium and phosphate ions are released into the environment and used by other organisms

Answer 38

Phosphate ions in rocks are eroded into the sea These can be absorbed and assimilated by plants This is consumed by animals and is then excreted This accumulates phosphate ions from waste, bones, guano, and shells This is eroded directly into the sea or deposited and forms rocks which are eventually eroded into the sea

Answer 39

Stimulus is detected by a receptor (sensory neurone) which sends an impulse to a coordinator (spine or brain) via relay neurones, which sends an impulse to an effector (motor neurone) which results in a response These are important because They are rapid They protect against damage to body tissues They do not have to be learnt They help escape from predators They enable homeostatic control

Answer 40

SAN releases wave of depolarisation across the atria, causing it to contract The AVN releases another wave of depolarisation when the first reaches it There is a slight delay so ventricles don’t contract before the atria can fully empty There is a non conductive layer between atria and ventricles to prevent the wave of depolarisation from travelling down the ventricles the bundle of His runs through the septum and passes the wave of depolarisation to the purkyne fibres in the walls of the ventricles The walls of the ventricles contract from the apex upwards The cells repolarise and cardiac muscles relaxes

Answer 41

Plasma membranes of the sensory neurones contain channel proteins that allow ion transportation They are stretch mediated sodium channels which open and allow sodium ions to diffuse into the sensory neuron when they are stretched and deformed In the resting state, sodium ion channels are too narrow for sodium ions to diffuse in so the resting potential is maintained When the pressure is applied, the stretch-mediated sodium channels are deformed and widen so sodium ions diffuse in and a generator potential is established

Answer 42

Stimulus provides the energy for voltage gated sodium ion channels in the exon membrane to open This causes sodium ions to diffuse in, increasing the positivity inside the axon This causes more voltage gated channels to open so more sodium ions diffuse in When wa threshold of +40mV is reached inside the axon, the voltage gated sodium channels close and voltage gated potassium channels open so potassium ions diffuse out The axon is depolarised (becomes more negative again) The axon temporarily becomes more negative than -70mV and is hyperpolarised Potassium ion gates shut and the sodium potassium pump restores the resting potential

Answer 43

Action potential arrives at presynaptic knob, depolarising it This leads to the opening of calcium ion channels and calcium ions diffuse in, pushing vesicles containing neurotransmitter to move towards and fuse with the presynaptic membrane This releases neurotransmitter into the synaptic cleft and it diffuses down a concentration gradient to the postsynaptic membrane Neurotransmitter binds to complementary receptors on the surface of the postsynaptic membrane This causes sodium ion channels on the membrane to open and sodium ions to diffuse in If enough neurotransmitter binds, then enough sodium ions diffuse in and the membrane potential is raised above the -55mV threshold The postsynaptic neurone is depolarised and neurotransmitter is recycled back to the presynaptic neurone Sodium ion channels close and the postsynaptic neuron re establishes the resting potential

Answer 44

Similarities Both unidirectional due to neurotransmitter receptors only being on the postsynaptic membrane Differences Nm only excitatory whereas synapse can be excitatory or inhibitory Nm connects motor neurone to muscles, synapse connects two neurones: sensory, motor, or relay Nm is the end point for an action potential, in synapses a new action potential is generated in the next neurone Nm acetylcholine binds to receptors on the muscle fibre membranes, in synapses it binds to receptors on the postsynaptic membrane of a neurone

Answer 45

Action potential reaches a muscle and calcium ions enter, causing the protein tropomyosin, which blocks the binding sites on the actin, to move and uncover the binding sites Whilst ADP is attached to the myosin head, it can bind to the binding sites on the actin, forming a cross bridge The angle in the cross bridge creates tension, pulling the actin filament and causing it to slide along the myosin This causes a molecule of ADP to be released so an ATP molecule can bind to the myosin head, causing it to change shape/bend, detaching from the actin ATP hydrolase is activated by the calcium ions and hydrolyses ATP on the myosin into ADP, releasing energy for the myosin head to return to its original position and the entire process can repeat

Answer 46

Alpha cells in the islets of Langerhans detect a fall in blood glucose and secrete glucagon into the blood plasma This attaches to specific receptors on the cell surface membrane of liver cells to stimulate glycogenolysis and gluconeogenesis to increase blood glucose concentration Beta cells in the islets of Langerhans detect a rise in blood glucose and secrete insulin Insulin binds to glycoprotein receptors on cell surface membranes and increase the rate of glucose absorption in cells as it changes the tertiary structure of glucose co transport carrier proteins, and causes more channels to form It also causes an increased respiratory rate so glucose is used up It can stimulate glycogenesis in the liver to lower blood glucose concentration

Answer 47

Gluconeogenesis occurs when all glycogen has been hydrolysed and blood sugar concentration is still too low It creates glucose from non-carbohydrate stores - usually from amino acids and glycerol Glycogenolysis occurs when blood glucose is too low It hydrolyses glycogen to glucose so glucose can move into the bloodstream by facilitated diffusion Glycogenesis occurs when blood glucose is too high It converts excess glucose into glycogen to be stored in the liver

Answer 48

Released by the adrenal glands in times of excitement or stress It binds to protein receptors on the cell surface membrane of liver cells This causes the protein to change shape and activates the enzyme adenylate cyclase This converts ATP to cAMP which acts as a second messenger and binds to protein kinase enzyme This changes shape and catalyses glycogenolysis

Answer 49

Type 1 occurs because the body is unable to produce insulin It can be the result of an autoimmune disease where beta cells are attacked This means beta cells don’t secrete insulin when blood sugar is high So glycogenesis is not stimulated and glucose isn’t converted to glycogen, glucose uptake into cells is not stimulated It can be treated with insulin injections or pancreas transplant Type 2 occurs as receptors on target cells lose their responsiveness to insulin This means that insulin is still secreted but it doesn’t bind to cell surface membrane receptors so the tertiary structure of glucose co transport carrier proteins isn’t changed and more glucose isn’t absorbed, glycogenesis isn’t stimulated

Answer 50

High blood/hydrostatic pressure Forces small substances like water, glucose, ions, and urea Through small fenestrations in the capillary endothelium And through the basement membrane

Answer 51

Ions, small molecules, and water are reabsorbed from the ultra filtrate back into capillaries surrounding the proximal convoluted tubule Cells have microvilli for a larger surface area They have channel/carrier proteins for facilitated diffusion They have carrier/co-transport proteins for active transport They have mitochondria to supply ATP for active transport They have ribosomes to produce channel/carrier proteins

Answer 52

Na+ moves out of the ascending limb by active transport into the interstitial fluid The increase in Na+ lowers the water potential of the i.f Na+ diffuses into the descending limb Water moves out of the descending limb by osmosis into the i.f, it then enters the capillaries and is removed The water potential towards the base of the descending limb is lowered due to the movement of water out by osmosis Na+ moves out of the base of the ascending limb by diffusion and out of the upper region by active transport, again lowering the water potential of the i.f A water potential gradient is created in the i.f between the ascending limb and the collecting duct, with water potential lowering further into the medulla This gradient is maintained by the fact that the ascending limb is impermeable to water

Answer 53

When ADH reaches the kidney, it binds to receptors on the cell membranes of the DCT and the collecting duct This activates a phosphorylase enzyme in the cells This causes the vesicles containing aquaporins to fuse with the cell membrane, resulting in more embedded aquaporins - these are protein channels for water to pass through This means more water leaves the DCT and collecting duct and is reabsorbed into the blood

Answer 54

Populations are geographically separated and so reproductively isolated - no gene flow between populations Within the separate gene pools there is genetic variation due to mutation (and sexual reproduction) In different environments there are different selection pressures There is differential reproductive success - natural selection occurs in each population Over time the allele frequency changes Eventually different species are formed that cannot interbreed to produce fertile offspring

Answer 55

Populations are within the same habitat but become reproductively isolated There are separate gene pools In each population, different alleles are passed on Natural selection occurs Over time, the allele frequency changes Eventually different species are formed that cannot interbreed to produce fertile offspring

Answer 56

Pioneer species such as lichen colonise bare rock/sand The pioneer species are adapted to survive harsh abiotic factors Their death and decomposition change the abiotic factors to become less harsh and from a thin layer of soil called humus Moss and smaller plants can then survive and they further increase the depth and nutrient content of the soil This pattern continues, with abiotic factors continuing to be less harsh, larger plants surviving, and the environment being further changes Each new species may change the environment in a way that makes it less suitable for the previous species, so each existing species is outcompeted The final stage in a succession is known as the climax community - this is dominated by trees

Answer 57

Random sampling can be used to investigate non motile organisms with uniform distribution It involved generating random coordinates and placing quadrats then calculating mean coverage Line transects and quadrats can be used to investigate non motile organisms with uneven distribution This can be used to investigate the effects of certain factors on distribution Mark release recapture can be used to estimate the population of motile organisms An initial sample is collected and marked in a way that is non toxic, weather resistant, and doesn’t impact reproduction or predation These are then released and left to redistribute A second sample is collected and the number of marked individuals is counted (No. originally caught x no. in second sample)/no. marked and recaptured

Answer 58

Inversion - a series of bases detach and rejoin but inverted, resulting in different amino acids being coded for Deletion - one base is deleted from the sequence which causes frameshift to the left Addition - an extra base is added which causes frameshift to the right Substitution - a base is swapped for another base - can be silent Duplication - the same base or series of bases is copied in many times, this results in a frameshift Translocation - section of bases detaches and attaches to a different chromosome, this has significant impacts on gene expression and the resulting genotype

Answer 59

Totipotent - can divide to produce any body cell including placenta and are found in early mammalian embryos Pluripotent - can become almost any type of cell and are found in embryos Multipotent - can divide to form a limited number of cell types, found in mature mammals, like bone marrow cells Unipotent - can only differentiate into one type of cell e.g cardiomyocytes Induced pluripotent stem cells are produced from adult somatic cells with genes switched back on using TF

Answer 60

Increased methylation means more methyl groups added to DNA by attaching to cytosine This prevents TF from binding and attracts proteins that condense the DNA-histone complex This reduces transcription Decreased acetylation means acetyl groups are removed from DNA This means histones become more positive and are attracted to the negative phosphate groups on DNA This makes DNA and histones more strongly associated so it is harder for TF to bind This reduces transcription

Answer 61

Mutation occurs in tumour suppressor gene which inactivates it It stops producing proteins to slow cell division and cause cell death if DNA copying errors are detected Cell divisions continue and mutated cells not identified Leads to rapid uncontrolled cell division Proto-oncogenes mutate to oncogenes This creates a protein that stimulates the initiation of DNA replication and mitotic cell division This can be permanently activated leading to rapid uncontrolled cell division

Answer 62

Temperature is increased to 95oC to break the hydrogen bonds and separate the DNA into single strands (denaturing) Temperature decreased to 55oC so primers can attach (annealing) Temperature increased to 72oC and free nucleotides associate with their complementary base pairs Enzyme taq DNA polymerase forms phosphodiester bonds between adjacent nucleotides, synthesising a new strand of DNA

Answer 63

Sample collected and DNA extracted by cell fractionation and ultracentrifugation PCR used to amplify the amount Restriction endonucleases used to cut DNA into fragments around target VNTRs DNA samples loaded into wells in agar gel which is submerged in a buffer liquid with electrical voltage applied DNA is negative so moves through the gel towards the positive electrode Gel creates resistance so smaller pieces of DNA move faster and further - different VNRs are separated heat/alkali is applies to separate the double stranded DNA radioactively/fluorescently labelled probes are mixed with the VNTRs These are transferred to a nylon sheet and exposed to x-rays/UV to visualise the position of the probes DNA bands can be compared to identify genetic relationships

Extended response qu Flashcards

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