Topic 1: Lifestyle, Health and Risk

Explain the importance of water as a solvent in transport, including its dipole nature. (2).

June 2010: Water is described as a dipolar molecule because it has a:Positively charged hydrogen end and a negatively charged oxygen end

Distinguish between monosaccharides, disaccharidesand polysaccharides (glycogen and starch amylose and amylopectin) and relate their structures to their roles in providing and storing energy (3).

June 2009: Triglycerides are composed of: 1 glycerol molecule and 3 fatty acid moleculesThe bond between a glycerol molecule and a fatty acid molecule is:An ester bondThis bond is formed by: CondensationUnsaturated lipids: Have double bonds between carbon atoms and between carbon and oxygen atoms Saturated lipids have: more hydrogen atoms than unsaturated lipids

June 2010: The questions below refer to some important biological molecules: Disaccharides can be split by: Hydrolysis of glycosidic bondsAmylose is an example of a:PolysaccharideThe role of starch is to:Store energy in plantsProteins are polymers of amino acids joined by peptide bonds formed between the:Carboxyl group and the amino group

January 2012: Fats and carbohydrates such as glycogen are important energy storage molecules. These are broken down during exercise. Describe the structure of glycogen and explain why it is a suitable molecule for storing energy.Structure: Consists of () glucose Joined by 1,4 / 1,6 glycosidic bonds Branched structure Idea of compact structureFunction: Idea that it is easily / rapidly hydrolysed Leading to more glucose in a smaller space in a cell Idea of low solubility It does not diffuse out of cells It has no osmotic effect (large etc)

January 2012: A carbohydrate-loading diet is used by athletes in preparation for some athletic events. This diet involves increasing carbohydrate intake and decreasing activity, several days before the event. Carbohydrate-loading is not a suitable method of preparation for all athletic events. Using your knowledge of glycogen, explain what type of athletic event could be prepared for using a carbohydrate-loading diet Idea that this diet is suitable for a high intensity event Credit suitable example of athletic event e.g. any endurance or power event Reference to carbohydrate being stored as glycogen Idea of maximum / more / lots of glycogen stored Idea that breakdown of glycogen provides energy for the eventJune 2012: Carbohydrates are important components of our diets. Distinguish between the structures of each monosaccharides and disaccharides and amylose and amylopectin of carbohydrate molecules.Monosaccharides and disaccharides: Idea that a monosaccharide consists of one sugar / named sugar / unit whereas a disaccharide consists of two sugar units Idea that disaccharide has a glycosidic bond whereas monosaccharide does not General formula for a monosaccharide is CnH2nOn whereas formula for disaccharide is CnH2n-2On-1Amylose and amylopectin: Amylose is straight chained / unbranched whereas amylopectin is branched Amylose coiled whereas amylopectin is not Amylose has 1-4 glycosidic bonds whereas amylopectin has 1-4 and 1-6 glycosidic bonds

January 2013: Enzymes act as biological catalysts. Amylase is an enzyme present in saliva that catalyses the hydrolysis of starch into maltose. Describe the structure of starch. glucose Glycosidic bonds / links Amylose and amylopectin Amylose has 1- 4 glycosidic bonds / links AND amylopectin has 1- 4 and 1- 6 glycosidic bonds Amylose is spiralled / coiled Amylopectin is branched Compact molecule

January 2013: Explain the meaning of the following terms: catalyst and hydrolysis.Catalyst: Speeds up the rate of reaction Without being changed / used up Lowers activation energy / provides an alternative reaction pathway Does not change products / position of equilibriumHydrolysis: Breaks the glycosidic bonds Reference to use of water

January 2013: Bread contains a high proportion of starch. If bread is chewed for a long period of time it begins to taste sweet. Suggest why bread tastes sweet after chewing for a long period of time.Idea that maltose / disaccharide / glucose / monosaccharide is produced and so tastes sweet.

Describe how monosaccharides join to form disaccharides (sucrose, lactose and maltose) and polysaccharides (glycogen and amylose) through condensation reactions forming glycosidic bonds, and how these can be split through hydrolysis reactions.(4)

June 2011: In the space below, draw a diagram to show the products formed when galactose and glucose molecules join together to form lactose. Both hexose molecules in disaccharide correctly drawn Indication that water is formed Glycosidic bond correctly drawn

June 2011: Name the chemical reaction that joins the galactose and glucose molecules together.Condensation reaction (polymerisation)

June 2011: Name the bond that joins the galactose and glucose molecules together.1-4 glycosidic bond

Describe the synthesis of a triglyceride by the formation of ester bonds during condensation reactions between glycerol and three fatty acids and recognise differences between saturated and unsaturated lipids.(5)

January 2011: Show the synthesis of a triglyceride by a condensation reaction.

Explain why many animals have a heart and circulation (mass transport to overcome limitations of diffusion in meeting the requirements of organisms).(6)

January 2010: the table below refers to blood flow in the four major blood vessels of the human heart. If the statement is correct, place a tick in the appropriate box and if the statement is incorrect, place a cross in the appropriate box.Name of blood vesselCarries blood away from heartCarries oxygenated blood

Aorta tick tick

Vena cavacross (X) cross (X)

Pulmonary artery tick cross (X)

Pulmonary ven cross (X) tick

January 2010: Describe the circulation of blood in a fish. Blood flows from heart to gills Blood flows from gills to rest of body Blood flows from body back to heart Ref to single circulation

January 2010: Suggest the advantages that the human circulatory system has compared with that of a fish. Blood flows faster/at higher pressure to the body Blood flows slower/at lower pressure to the lung Idea that this reduces risk of damage to lungs Correct ref to more efficient exchange/ transport of gases

January 2010: The heart of an insect is a long tube. It pumps blood into the body cavity so that blood surrounds the cells. The blood then passes back into the heart from the body cavity. Suggest why the insect does not need blood vessels to transport its blood around the body. Correct ref to large surface area to volume ratios Idea that all cells are very close to the blood / heart Idea that diffusion is fast enough for exchange of nutrients / gases / waste Idea of low metabolism Idea that movement of blood back into the heart is fast enough to return blood back into the heart

June 2010: Read through the following passage about the heart and its major blood vessels, added on the dotted lines are the most appropriate word or words to complete the passage.The mammalian heart consists of four chambers, two upper chambers called ....................atria........................... and two lower chambers called ventricles.The ..................aorta............................. carries oxygenated blood away from the .....................left.......................... ventricle to the cells of the body and the pulmonary ..................artery............................. carries deoxygenated blood to the lungs. The vena cava............................. returns deoxygenated blood back to the heart from the body.

January 2011: Give one reason why many animals have a circulatory system.Idea that it overcomes limitations of diffusion / it is involved in transport / heat transfer.

January 2011: Explain why a mammalian heart is divided into a right side and a left side. Idea that it keeps oxygenated and deoxygenated blood separate Idea that this results in as much oxygen as possible being carried to the tissues / cells Reference to different pressures in each side / need for different pressures explained

June 2012: Many animals, such as mammals, have a heart and circulation. This helps them to meet their requirements by overcoming the limitations of diffusion. Describe the structure of the mammalian heart. Idea that there are four chambers Correct reference to relative position of atria and ventricles Idea of left and right sides separate / septum Reference to muscular nature of walls Reference to cardiac muscle Idea of relative thickness of ventricle walls Correct reference to position of atrioventricular valves Correct reference to position of semilunar valves Reference to position of tendons / tendinous cords / papillary muscles Correct reference to position of aorta / pulmonary artery Correct reference to position of vena cava / pulmonary vein Correct reference to coronary arteries Reference to SAN / Sino Atrial Node / pacemaker/ AVN /Atrioventricular Node / Purkinje fibres /Purkyne fibres / Bundle of His

June 2012: Using your own knowledge, explain the importance of the heart and circulation to a giraffe. Idea that the heart has to pump blood a long way around the body of the giraffe Therefore blood needs to be pumped at high pressure Blood vessels are needed to contain the blood / reference to closed circulation Idea of double circulatory system Capillaries needed to ensure that all parts of giraffe are close to blood supply Idea of need for a circulation to provide oxygen / remove carbon dioxide / other correct named substance Idea of oxygen / glucose needed as high metabolic rate / high rate of respiration Idea of diffusion not meeting the requirements of the giraffe Reference to low surface area to volume ratio Idea that circulatory system helps regulation of body temperature

June 2012: Suggest why there are changes to the available energy (ATP) in the heart muscle cells following the loss of blood flow. Idea of less / no oxygen available Idea of less / no respiratory substrate / glucose Less / no cellular / aerobic respiration

Describe the cardiac cycle (atrial systole, ventricular systole and diastole) and relate the structure and operation of the mammalian heart to its function, including the major blood vessels. (7)

June 2009: State whether the atria and ventricles are contracted or relaxed in each of these stages: atrial systole, ventricular systole, diastole:Atrial systole: atria contracted, ventricles relaxedVentricular systole: atria relaxed, ventricles contracted Diastole: atria relaxed, ventricles relaxed

June 2009: Describe the roles of the atrioventricular (bicuspid and tricuspid) valves during the cardiac cycle. valves separate atria from ventricles open during atrial systole/contraction so that blood can pass through to ventricles closed during ventricular systole/ contraction to prevent blood being forced back /backflow / up into atria to maintain pressure in ventricles open during diastole so that ventricles can start to fill up as atria are filling

June 2009: During the cardiac cycle, the pressure in the right ventricle rises to a maximum of about 3.3 kPa. Suggest reasons for the difference between this pressure and the maximum pressure in the left ventricle. Correct reference to pressure differences e.g. left is higher Left ventricle pumps blood all around body/ to rest of body / many arteries / systemic Right ventricle pumps blood to lungs/ pulmonary system. Idea that if blood under high pressure there would be damage to lungs / capillaries Reference to lots of muscle contracting in left ventricle / reference to thick wall of left ventricle

January 2013: Read through the following passage on the cardiac cycle, on the dottedlines the most appropriate word or words have been written in to complete the passage.The cardiac cycle consists of three stages: atrial systole, ventricular systole and ....................diastole.................... .During atrial systole, the ..........atria............. contract and the..........................ventricles............ are relaxed. The ..........atrioventricular............ valves are open. During ventricular systole, the .semilunar valves.................... open as oxygenated blood is forced out of the heart through the aorta to the body and through the pulmonary................artery...................... to the lungs.

Explain how the structures of blood vessels (capillaries, arteries and veins) relate to their functions. (8)

January 2011: The table below refers to the structure of capillaries and veins.Type of blood vesselValves present along the length of the vesselWall consists of single layers Endothelial cells present

Capillary NoYesYes

VeinYesNoYes

January 2011: Semilunar valves and elastic fibres are found in the aorta.For each of these structures, describe its location in the aorta and explain its function.Semilunar valves: Located at the base of aorta Prevents backflow of blood into heart / ventricles) During diastole/atrial systoleElastic Fibres: Middle layer of wall of vessel / tunica media / in the muscle layer Reference to allows stretching / recoil / description To prevent damage of the aorta / to maintain the pressure of the blood

January 2013: Explain how the structure of the aorta relates to its function. Idea that there is a thick wall / lots of collagen / thick layers / thick tunica media (ALLOW idea of folded wall) idea that it needs to avoid rupture / to withstand high pressure (IGNORE damage alone ALLOW stretch to accommodate more blood) Elastic / muscular/ layer / fibres / wall controlS the flow of blood / maintain blood pressure / elastic recoil (ALLOW to squeeze blood along smooth endothelial wall to reduce friction / resistance Semi lunar valve present to prevent backflow of blood into the heart during diastole Large lumen (IGNORE narrow lumen) idea of accommodating large volumes of blood Branches to supply blood to different parts of the body including coronary arteries

January 2013: Describe two differences between the structure of a capillary and the structure of a vein. Capillary walls are one cell thick No elastic tissue / collagen / muscle / multiple layers in the capillary walls No valves in capillaries Capillaries have a very narrow lumen Capillaries are porous / have pores

Describe how the effect of caffeine on heart ratein Daphnia can be investigated practically, and discuss whether there are ethical issues in the use of invertebrates. (9)

January 2010: Describe an experiment that the student could perform, using Daphnia, to confirm that herbal tea has the lowest caffeine content. Idea of heart rate determined before treatment Idea that daphnia need to be put into tea and allowed to acclimatise Practical detail e.g.use of microscope Details of determining heart rate described Ref to named controlled variable Ref to repeats / replicates Idea that heart rate of daphnia determined in white tea only / known caffeine concentration

January 2010: Give one ethical reason for the use of invertebrates and one ethical reason against the use of invertebrates in experiments of this type. For:Daphnia are very simple organisms / Daphnia have basic nervous system Against:Use of (any) animal is wrong / how can we be sure what the Daphnia can feel / ref. to possibility that the Daphnia could die

January 2013: An investigation was carried out to study the effect of caffeine on the heart rate of a chicken embryo. The heart from a chicken embryo was removed and placed in a glucose solution. The heart rate was determined and recorded as the base heart rate. The experiment was repeated using glucose solutions containing five different concentrations of caffeine. The heart rate was determined and recorded as a percentage of the base heart rate for each solution. Suggest why glucose was included in the solutions. Glucose provides respiratory substrate To provide energy for heart muscle contraction Reference to osmotic effectJanuary 2013: Suggest how the caffeine solutions were prepared to obtain valid results.Glucose / pH at same concentration / volume / value. January 2013: State how these results could be made more reliable.Reference to replication procedure.January 2013: Describe how this investigation could be carried out using Daphnia instead of chicken embryos. Details of method to limit movement of Daphnia e.g. use of cotton wool IGNORE cavity slide Reference to determining base heart rate in absence of caffeine ALLOW measure heart rate in 0% caffeine NOT distilled water Reference to use of range of caffeine concentrations Acclimatisation of Daphnia in each solution Details of method to determine heart rate e.g. dots on paper in a set time / use video camera IGNORE just counting Repeats / replicates Named control variable e.g. source / size / age / type / of Daphnia, temperature, pHJanuary 2013: Suggest one ethical issue in the use of chicken embryos in this investigation.Chicken embryo is a vertebrate / feels pain / will die / cannot give consent

Describe the blood clotting process (thromboplastin release, conversion of prothrombin to thrombin and fibrinogen to fibrin) and its role in cardiovascular disease (CVD).(10)

January 2010: There are many venomous (poisonous) snakes in the world. Many of the venoms from these snakes affect the blood clotting process. Describe the blood clotting process. Idea that there is a cascade of events leading to blood clotting Ref to thromboplastin starting the cascade Ref to conversion of prothrombin into thrombin Idea that thromboplastin / thrombin is an enzyme / a catalyst Ref to conversion of fibrinogen in to fibrin Ref to formation of mesh of fibres/fibrin Ref to requirement of calcium ions/ Ca2+ / vitamin K Ref to platelets/blood cells getting trapped in the mesh

June 2010: Using your own knowledge of the blood clotting process, suggest why frequent cocaine use could increase the risk of a blood clot forming with the knowledge that the von Willebrand factor is involved in platelets sticking to each other and platelets sticking to the endothelial lining of blood vessels . Idea that von Willebrand factor results in platelets sticking to the endothelium / each other. Reference to release of thromboplastin from platelets. As a result the blood clotting process is triggered. Credit one correct detail of clotting process. Reference to more fibrinogen resulting in the clot being larger / growing faster. Reference to von Willebrand factor making the platelets stickier. As a result of platelet stickiness / platelets sticking together the clot grows faster / blood flow is decreased. If the blood is flowing slower then there is an increased chance of blood clotting

June 2013:

Explain the course of events that leads to atherosclerosis (endothelial damage, inflammatory response, plaque formation, raised blood pressure).(11)

June 2009: One cause of coronary heart disease is atherosclerosis. Describe how atherosclerosis develops. Damage to endothelial cells / epithelial cells / cells lining artery wall Reference to inflammatory response Reference to accumulation of white blood cells in damaged area Buildup of cholesterol in damaged area Reference to buildup of calcium salts / fibrous tissue / fibrin / platelets Reference to formation of atheroma/ plaque Reference to loss of elasticity of artery / narrowing of lumen Idea that this process is selfperpetuating

January 2011: Cardiovascular diseases are very common in the Western World. (a) Many cardiovascular diseases result from atherosclerosis.Atherosclerosis usually results from the formation of plaques inside: Arteries The plaques begin to form after damage to:Endothelial cells These cells may be damaged due to:Blood flowing quickly under high pressureThe plaque consists of:Fatty depositsThe presence of a plaque in the vessels supplying blood to the brain could result in:A stroke

January 2012: Cardiovascular disease (CVD) is responsible for many deaths. One cause of CVD is atherosclerosis. Describe how atherosclerosis develops. Damage to endothelial cells/ epithelial cells / lining of artery Ref to inflammatory response Ref to migration of white blood cells into area Build up of cholesterol Reference to formation of atheroma / plaque Reference to calcium salts / fibrous tissue Ref to loss of elasticity of artery / narrowing of lumen Idea that this process is selfperpetuating

Describe the factors that increase the risk of CVD (genetic, diet, age, gender, high blood pressure, smoking and inactivity). (12)

June 2010: Name two factors that increase the risk of CVD. Genetic Diet qualified Increasing age Being male High blood pressure Smoking, Inactivity / lack of exercise

June 2011: Risk calculators can be used to estimate the probability that a person will develop CVD. Many of these calculators start by asking for the age and gender of the person using them. Explain why information about age and gender is important in estimating the risk of developing CVD. Age effect qualified e.g. older increases risk, arteries become less elastic / more easily damaged / blood pressure increases with increase in age Gender effect qualified e.g. women less likely to develop CVD than men / oestrogen offers some protection to women against CVD pre menopause.

January 2012: Give two factors, other than genetic factors, that increase the risk of developing CVD.More saturated fat / more cholesterol / more salt /obesity / more alcohol / more age / male / post- menopausal women / high blood pressure / smoking / diabetes / less activity / stress.

January 2013: State two factors, other than obesity, high blood pressure and high blood cholesterol, that increase the risk of CVD.Any two from: Being male Increase in age Lack of exercise / inactivity Smoking Genetics High alcohol consumption high salt diet High saturated fat intake stress Diabetes

Describe the benefits and risks of treatments for CVD (antihypertensives, plant statins, anticoagulants and platelet inhibitory drugs).(13)

January 2011: State the risks of using antihypertensives.Blood pressure falls too low / coughs / swelling of ankles / impotence / tiredness / constipation / headache / confusion / depression / excessively low heart rate / allergy / stroke / provoked type II diabetes / frequent urination / fainting / dizziness / vomiting / dry mouth / breathing difficulties / irregular heart rate / chest pain / hives / rash / dehydration / reduced circulation effects / low potassium / blurred vision.

January 2012: Trials have shown that plant statin therapy is more effective in 719 Arg carriers than in non-carriers of this allele. Describe the risks of using plant statins to treat CVD. Muscle inflammation / pain Liver damage / failure Joint aches / pains Nausea / constipation / diarrhoea Kidney damage / failure Cataracts Diabetes Allergies / skin inflammation / skin rash Respiratory problems / persistent cough Headaches / dizziness / depression

June 2012: Give the name of the type of drug that is used to treat high blood pressure.Antihypertensives / antihypertensive drug / beta blockers / diuretics / ACE inhibitors / calcium ion channel blockers / vasodilators.

June 2012: Explain why many patients, who are over 80 and have high blood pressure, are routinely prescribed with drugs such as antihypertensives. High blood pressure can cause / increases risk of CVD / correctly named complication / description Idea that older people are more at risk of CVD

Analyse and interpret data on the possible significance for health of blood cholesterol levels and levels of high-density lipoproteins (HDLs) and low-density lipoproteins (LDLs). Describe the evidence for a causal relationship between blood cholesterol levels (total cholesterol and LDL cholesterol) and CVD.(14)

June 2011: Explain how lowering blood cholesterol levels can reduce the risk of CVD. Less cholesterol in blood to build up on artery wall Less likely to develop atherosclerosis Credit correct reference to subsequent consequence of atherosclerosis e.g. narrowing of arteries, ischaemia, decrease in flow of blood to heart.

Discuss how people use scientific knowledge about the effects of diet (including obesity indicators), exercise and smoking to reduce their risk of coronary heart disease.(15)

June 2009: Suggest reasons for a change in the number of deaths from CHD. People more aware of the dangers / better health education / appropriate named example Less stress Better / more screening Better treatments More exercise being taken Changed diet / less obesity Less alcohol intake Decrease in smoking Change in population genetics

January 2010: Cardiovascular disease (CVD) is responsible for many deaths.Describe two changes that this woman may be able to make to her lifestyle, to reduce her risk of dying from CVD. Explain how each change would reduce the risk. Idea that the woman could reduce her energy intake weight / BMI decreases if her energy expenditure greater than intake. Diet should have reduced cholesterol levels cholesterol has been associated with high blood pressure / atherosclerosis. Diet should have reduced saturated fat reduces blood cholesterol / LDL Idea that the woman could increase the amount of exercise she took weight decreases if energy expenditure is greater than her intake / exercise helps maintain a healthy heart / reduces blood pressure. Idea that if the woman smoked she should reduce it smoking reduces oxygen uptake / increases stickiness of platelets / increases blood pressure / increases risk of atheroma. Idea that diet should have reduced salt high salt associated with high blood pressure. Idea of moderate alcohol intake high alcohol associated with high blood pressure.

June 2011: Give three other ways apart from lowering blood cholesterol levels and lowering blood pressure in which the risk of CVD may be reduced. Decrease in smoking / not smoking Reference to increase / regular exercise Improvements to diet qualified,e.g. reduce salt, reduce saturated fat, increase fibre Maintaining appropriate weight Moderate / reduced alcohol consumption Reducing stress Use of medication e.g. statins, antihypertensives, warfarin

January 2013: Suggest two reasons for the overall decrease in high blood cholesterol as a risk factor. People more aware of the risks people consuming foods with lower cholesterol levels / saturated fats People consuming foods with more fibre in them Use of statins More screening More exercise

Describe how to investigate the vitamin C content of food and drink. (16) June 2009: Describe how an investigation could be carried out to compare the effect of storage time on the vitamin C content of the Parana state camu-camu fruit with those from the Amazon region. Reference to DCPIP Reference to use of camu-camu juice Idea of titrating juice with DCPIP Correct reference to colour change e.g.from blue to colourless / pink. Use of calibration curve to determine vitamin C concentration / comparison with standard vitamin C Reference to procedure being repeated at (regular) time intervals e.g. everyday. Reference to replication Description of one controlled variable Reference to drawing graph of both sets of results

June 2011: It has been suggested that cooking food in a microwave oven does not reduce the nutrient content of foods by as much as cooking in boiling water. A student wanted to test this idea on the vitamin C content of carrots. Describe an investigation that the student could carry out to compare these two methods of cooking on the vitamin C content of carrots. Idea that some carrots need to be boiled in water and some cooked in microwave Reference to control of appropriate variable Reference to juice / cooking water being used Reference to DCPIP Reference to titration / description of titration of juice Colour change of DCPIP e.g. from blue to colourless / pink as juice added / until stays blue as DCPIP added Reference to comparison of volumes of DCPIP added to each / use of calibration curve / calculation of vitamin C concentration against known vitamin C solution Reference to repeats

Analyse data on energy budgets and diet so as to be able to discuss the consequences of energy imbalance, including weight loss, weight gain, and development of obesity. (17) June 2011: Suggest why exercise is usually included as part of a weight loss programme. Idea that exercise uses energy The longer / more intense the exercise, the more energy used / weight loss Idea of mass / weight loss depends on energy input lower than energy output Idea that exercise increases metabolism / muscles use more energy than fat

June 2012: Explain why a diet consisting of a high proportion of carbohydrates could lead to obesity. Idea of carbohydrates providing a source of energy if the energy / carbohydrate input is greater than the energy output / carbohydrate use weight will be gained Idea of excess carbohydrate converted to fat

Analyse and interpret quantitative data on illness and mortality rates to determine health risks (including distinguishing between correlation and causation and recognising conflicting evidence).(18)

June 2009: Distinguish between the terms causation and correlation:Causation: when a change in one variable is responsible for a change in another variable.Correlation: relationship between two variables such that a change in one of the variables is reflected by a change in the other variable. June 2010: It has been suggested that there is a correlation between the change in the concentrations of fibrinogen in the blood and the increased risk of heart disease due to cocaine use. Explain why this suggestion is valid. Idea that a correlation is a relationship between two factors / when one factor changes another factor changes. Fibrinogen increases with cocaine use Heart attacks increase with cocaine use Idea that increased fibrinogen levels have not been shown to result in the increase in heart disease.

January 2012: Explain the meaning of the term correlation:A relationship between two variables is such that a change in one of the variables is reflected by a change in the other variable.

January 2013: There is evidence for a causal relationship between blood cholesterol levels and cardiovascular disease (CVD). Explain the meaning of the term causal relationship.Idea that a change in one variable directly results in the change of another variable.

Evaluate design of studies used to determine health risk factors (including sample selection and sample size used to collect data that is both valid and reliable). (19)

June 2010: Suggest why it is necessary to have so many people involved in a study on CVD. Idea that it makes the results/data/study representative / reliable Idea that there are many potential risk factors / large variation between individuals. Idea that side effects more likely to show up

June 2010: Suggest what the placebo could be in a study into CVD. Saline Water Sugar tablet Empty capsule

June 2010: Suggest why this study had to run for a number of years. Idea that CVD is not an immediate disease Side effects may take time to become apparent Need to see if drug works over a long time

Explain why peoples perceptions of risks are often different from the actual risks (including underestimating and overestimating the risks due to diet and other lifestyle factors in the development of heart disease).(20)

Topic 2: Genes and health

Explain how models such as the fluid mosaic model of cell membranes are interpretations of data used to develop scientific explanations of the structure and properties of cell membranes.(2)

June 2010: Describe the structure of a phospholipid. Phospholipids; Phosphate head Two fatty acid tails Reference to location of glycerol Correct reference to ester bonds

June 2010: Explain how the properties of a phospholipid contribute to the structure of the cell membrane. Reference to hydrophilic / polar / charged part Reference to hydrophobic/ non-polar/ uncharged part Reference to orientation of molecule in relation to water Idea that aqueous environment is on two sides / cytoplasm and environment / tissue fluid

June 2010: Describe how the results of an investigation showing that proteins from two different cells have intermingled in one cell after fusion can be explained by the fluid mosaic model. Idea that phospholipids / molecule A allow fluidity / movement Idea that fluidity/movement/eq}allow membranes to fuse Idea that fluidity / movement allows protein to move / intermingle

June 2012: The phospholipids form a bilayer because:The hydrophobic tails move away from the aqueous environment

June 2012: The fluidity of the membrane is determined by the proportion of:Cholesterol

January 2013: Molecules are transported across the cell membrane in a number of different ways. Describe the structure of a cell membrane. ALLOW a clearly labelled diagram Phospholipid bilayer Credit details of phospholipid bilayer e.g orientation because of hydrophobic and/or hydrophilic regions e.g. phospholipids are fluid Proteins Credit details of proteins e.g. description of channel/carrier protein structure or position intrinsic, extrinsic or transmembrane Reference to other named membrane component e.g. glycolipid, cholesterol, glycoprotein, carbohydrate chain, glycocalyx

Explain what is meant by osmosis in terms of the movement of free water molecules through a partially permeable membrane (3).June 2009: Explain the meaning of the term osmosis.Movement / diffusion / of water through a partially permeable membrane from a region with more free water to a region with less free water / down water concentration gradient.

June 2011: A student wanted to sweeten some strawberries, so she sprinkled some sugar on top of them, one hour before eating them. The student noticed that the sugar that she had sprinkled on them was no longer visible and that there was some juice at the bottom of the bowl. Using your knowledge of cell transport mechanisms and the properties of water, explain how the juice is formed from the water that came from the fruit. Correct reference to water gradient between sugar and strawberries Reference to osmosis of water from inside of strawberry to outside Idea that water is found i cytoplasm/ vacuoles of strawberry Reference to water as a solvent for the sugar Reference to (di)polar nature of water

Explain what is meant by passive transport (diffusion, facilitated diffusion), active transport (including the role of ATP), endocytosis and exocytosis and describe the involvement of carrier and channel proteins in membrane transport.(4)

January 2010: Give two differences between active transport and diffusion. Active transport is against concentration gradient. Active transport requires ATP energy. Ref to involvement of membrane proteins in active transport

June 2010: Some proteins in the cell membrane are involved in active transport and facilitated diffusion. Describe the role of proteins in these cell transport mechanisms.Active transport: Idea that molecule binds / fits into protein / carriers Idea that protein/carrier changes shape Molecules move against a concentration gradient Reference to use of ATP / energyFacilitated diffusion: Reference to proteins as channels/gates/ pores / carriers Idea that channels can open or close/ carriers change shape For large / polar / charged molecules to pass through membrane Molecules move down a concentration gradient

June 2011: Molecules are transported into and out of cells by several mechanisms.Read through the following passage that describes some of these mechanisms, the the most appropriate word or words have been added on the dotted lines to complete the passage.Some molecules move across a cell surface membrane by passing down aconcentration gradient, through the phospholipid bilayer. The movement of some polar molecules across the membrane involves carrier and channel ............................protein....................... molecules. When this movement occurs down a concentration gradient, the process is called ..facilitated diffusion ........................... and when it occurs against a concentration gradient the process is called ..active transport................................. .Energy in the form of ........................................ATP......................................... is used in the movement of molecules against a concentration gradient

June 2012: Suggest how oxygen passes from the cell membrane into the centre of an amoeba. Reference to diffusion in the cytoplasm Through the cytoplasm / description of part of cytoplasm Down a concentration gradient in the cytoplasm

Describe how membrane structure can be investigated practically, eg by the effect of alcohol concentration or temperature on membrane permeability.(5)

January 2011: The size and solubility of molecules has an effect on their ability to be taken up by cells. Describe an experiment you have carried out to investigate the permeability ofcell membranes. Appropriate tissue named e.g. beetroot Reference to washing / soaking beetroot thoroughly Reference to water bath to maintain / change temperature Reference to range at least 5 temperatures / alcohol concentrations Appropriate controlled variable named e.g. length of time, size of beetroot Indication of what is being used to judge permeability colour of solution, absorbance, transmission. Description of how permeability can be assessed e.g. use of colorimeter, standard solutions. Reference to repeats / replicate.

June 2010: Explain why it is necessary to measure the initial rate of reaction when investigating the effect of enzyme concentration on the rate of reaction. Idea that there should be enough substrate molecules to saturate the enzyme To ensure that substrate is not a limiting factor Fastest / highest rate / decreases after initial rate As reaction proceeds substrate concentration decreases As substrate gets used up by enzyme / in reaction Substrate concentration should be constant in each test

June 2010: In this investigation, the substrate concentration was a factor that was kept constant. Suggest two other factors that should be kept constant. For each factor, state how it can be kept constant. pH buffer Temperature water bath (not room temperature) Time of reaction stopwatch Volume of enzyme / substrate (not amount) measuring cylinder / pipette Type of enzyme same batch of enzym

June 2012: The action of lipase (enzyme) can be investigated using a triglyceride as the substrate. Describe an experiment, using lipase and a triglyceride, that could be carried out to collect data to plot a graph. Reference to use of a range of substrate (triglyceride) concentrations Idea of mixing enzyme and substrate Identification of a suitable dependent variable e.g. pH Description of how to measure the dependent variable e.g. use of pH indicator Reference to measuring time Description of how to calculate initial rate of reaction ; Idea of repeating experiment without the enzyme Idea of control of enzyme lipase concentration Reference to one other named controlled variable e.g. temperature, type of triglyceride, volume of solutions Reference to replicates / repeats using the same triglyceride concentration

Describe the properties of gas exchange surfaces in living organisms (large surface area to volume ratio, thickness of surface, difference in concentration) and explain how the structure of the mammalian lung is adapted for rapid gaseous exchange.(6)

January 2012: An amoeba is a single-celled organism that lives in water. Gas exchange in an amoeba occurs between the water and the cytoplasm. Using the your own knowledge, suggest how gas exchange occurs in organisms like an amoeba. Gas exchange occurs through the cell membrane / phospholipid bilayer Idea that the membrane is thin Oxygen enters cell from water Carbon dioxide leaves cell into water O2 / oxygen / CO2 / carbon dioxide are small / non-polar molecules Reference to diffusion Reference to / description of suitable concentration gradient Reference to large surface area to volume ratio

Describe the basic structure of an amino acid (structures of specific amino acids are not required) and the formation of polypeptides and proteins (as amino acid monomers linked by peptide bonds in condensation reactions) and explain the significance of a proteins primary structure in determining its three-dimensional structure and properties (globularand fibrous proteins and types of bonds involved in three- dimensional structure). (7)

January 2011: An enzyme is a protein and has a primary structure. Explain the meaning of the term primary structure. The sequence / order of amino acids Joined by peptide bond

January 2011: Using your knowledge of enzymes, explain the importance of the primary structure of an enzyme to its function. Idea that primary structure determines three-dimensional folding Reference to types of amino acids determine types of bonds / (other than peptide bonds) / named bond. Reference to position of amino acids determines position of bonds / correctly named bond Correct reference to two cys (aminoacids) form bonds Idea that shape / position / of active site is determined by position of amino acids Reference to shape of active site being correct to bind to substrate Reference to amino acids / R groups involved in chemical reaction Reference to globular / soluble / enzyme molecules being relatively short / small / made up of relatively few amino acids. Reference to globular / soluble proteins / enzyme having relatively high number of polar / small amino acids / R groups. Reference to polar R groups facing outwards

June 2011: The sequence of amino acids in a polypeptide chain is determined by the sequence of bases in DNA. This sequence of bases is used as a template to synthesise messenger RNA (mRNA). Describe the structure of an amino acid. Presence of amine group Presence of carboxyl group Reference to R group Reference to central carbon atom Award marks on correctly drawn diagram

January 2012: Proteins, such as enzymes, are important molecules found in all living organisms. Read through the following passage on the primary structure of proteins, where the most appropriate word or words have been written on the dotted lines to complete the passage. Proteins are made of monomers called amino acids............... . These monomers are joined together by .peptide .......................... bonds, formed during.condensation (polymerisation) reactions. Each monomer of a protein consists of a central carbon atom attached to a hydrogen atom, an R group, an ............amine......... group anda ..carboxyl (carboxylic acid). group. The sequence of monomers determines the primary structure of the protein.

January 2013: Lipoproteins are composed of phospholipids, cholesterol and proteins. (i) Proteins are made up of amino acids. Describe how amino acids join together to form the three-dimensional structure of a protein. Reference to peptide bonds joining amino acids Between amino group of one amino acid and carboxyl group of another The sequence of amino acids is the primary structure of the protein. Reference to folding of primary structure held together by bonds (ALLOW ref to alpha helix or beta pleated sheet) Disulfide bridges / hydrogen / H bonds / ionic bonds / Van der Waals forces ; Between the R groups

Explain the mechanism of action and specificity of enzymes in terms of their three-dimensional structure and explain that enzymes are biological catalysts that reduce activation energy, catalysing a wide range of intracellular and extracellular reactions. (8)

June 2009: Explain why melanin cannot be produced in the absence of the enzymetyrosinase. Idea that dihydroxyphenyalanine cannot be synthesised from tyrosine if tyrosinase is absent. Idea that precursor of melanin is dihydroxyphenylalanine / melanin only made if DHPA present. Enzymes are (substrate) specific therefore no other enzyme will breakdown tyrosine / tyrosine does not breakdown on its own.

January 2010: Describe the structure of an enzyme. Ref to an enzyme as a protein Ref to 3D/ tertiary / globular structure Ref to named bonds holding structure in place Between the R groups Ref to active site Idea of specificity of active site

June 2010: The three-dimensional structure of a protein is held together by: Disulphide bridges, hydrogen and ionic bonds

June 2010: Enzymes are biological catalysts that change the activation energy of chemical reactions. Explain the meaning of the terms biological catalyst and activation energy. Reference to enzymes / biological catalysts reducing activation energy.Biological catalyst: Produced by organisms / cells Speeds up rate of reactions / processesActivation energy: Energy needed for a reaction to occur By causing bonds to break / weaken / form by increasing the number of collisions

January 2012: Describe the three-dimensional (tertiary) structure of an enzyme. Globular Reference to active site Reference to specific shape of active site Reference to bonds / named bond / interaction between R groups Credit correctly named bond / interaction e.g. disulphide bond/bridges, hydrogen bonds, hydrophobic interactions between R groups.

January 2012: Explain how the primary structure of an enzyme determines its three-dimensional (tertiary) structure and its properties. Primary structure position / sequence / order of the amino acids / R groups Idea that this determines the positioning / type of the bonds / folding Determining the shape / properties of the active site Idea of interaction of active sites and substrates e.g. enzyme substrate complex forms Idea of polar / hydrophilic on the outside of enzymes / non polar / hydrophobic}on the inside Reference to solubility

Describe how enzyme concentrations can affect the rates of reactions and how this can be investigated practically by measuring the initial rate of reaction. (9)

June 2010: Explain why it is necessary to measure the initial rate of reaction when investigating the effect of enzyme concentration on the rate of reaction. Idea that there should be enough substrate molecules to saturate the enzyme To ensure that substrate is not a limiting factor Fastest / highest rate / decreases after initial rate As reaction proceeds substrate concentration decreases As substrate gets used up by enzyme / in reaction Substrate concentration should be constant in each test

June 2010: In this investigation, the substrate concentration was a factor that was kept constant. Suggest two other factors that should be kept constant. For each factor, state how it can be kept constant. pH buffer Temperature water bath (not room temperature) Time of reaction stopwatch Volume of enzyme / substrate (not amount) measuring cylinder / pipette Type of enzyme same batch of enzyme

January 2012: Describe how an inverted measuring cylinder under water could be used to compare enzyme activity in two different types of mussel. Reference to measuring volume of oxygen Suitable reference to time e.g. oxygen produced in unit time, time taken to produce same volume of oxygen Idea of measuring the initial rate of reaction Reference to controlled variable in relation to the mussel e.g. age, part of mussel, mass, surface area Reference to a controlled variable in relation to the experiment e.g. volume of hydrogen peroxide, temperature, concentration, pH Suitable reference to repeats

Describe the basic structure of mononucleotides (as a deoxyribose or ribose linked to a phosphate and a base,ie thymine, uracil, cytosine, adenine or guanine) and the structures of DNA and RNA (as polynucleotides composed of mononucleotides linked through condensation reactions) and describe how complementary base pairing and the hydrogen bonding between two complementary strands are involved in the formation of the DNA double helix.(10)

June 2009: In the space below, draw a diagram to show two mononucleotides joined together in a single strand of DNA (polynucleotide):

June 2009: Name an enzyme involved in DNA replication: DNA polymerase / ( DNA) ligase / (DNA) helicase.

June 2010: DNA consists of mononucleotides joined together by bonds between:One deoxyribose sugar and one phosphate group January 2010: Read through the following passage on the structure of DNA, the most appropriate word or words have been added on the dotted lines to complete the passageA DNA molecule consists of two strands of mononucleotides. Each of these strands is twisted around the other, forming a .double helix......................... .Each mononucleotide consists of a pentose sugar called .........................................deoxyribose................................. , a base and a .phosphate group................................................. . In each strand, the mononucleotides are held together by phosphodieter.......................... bonds. The two strands are held together by complementary base pairing. Adenine bondswith ..............................thymine............................................ and cytosine bonds with .............................guanine............................................. .The name of the bond that forms between these bases is a...................................hydrogen....................................... bond. A DNA molecule that is composed of 34% adenine will be composed of ..16%................................................... % cytosine.

June 2012: DNA and RNA are polynucleotides composed of mononucleotides joined by:Condensation reactionsJune 2012: The mononucleotides of RNA consist of a phosphate joined to the sugarRiboseJune 2012: The mononucleotides in mRNA are joined together byPhosphodiester bonds June 2012: The bases in RNA are:Adenine, cytosine, guanine and uracilJune 2012: DNA is a double stranded molecule twisted into:A double helix June 2012: The two DNA strands are held together by:Hydrogen bonds

Describe DNA replication (including the role of DNA polymerase), and explain how Meselson and Stahls classic experiment provided new data that supported the accepted theory of replication of DNA and refuted competing theories.(11)

January 2011: Describe the roles of messenger RNA (mRNA) and transfer RNA (tRNA) in protein synthesis.mRNA: Reference to mRNA as a copy of the genetic code / DNA Of the protein being synthesised Moves out of the nucleus / to ribosomes Idea that it acts as a template / has the instructions for translationtRNA: Correct reference to translation Binds to an amino acid / takes the amino acid to the ribosome / mRNA Reference to tRNA being specific to amino acid Holds the amino acid in place\

June 2011: In the late 1950s, Meselson and Stahl performed some important experiments. These experiments provided evidence to support the idea that new DNA was synthesised by semi-conservative replication. Name an enzyme involved in DNA replication. DNA polymerase DNA helicase DNA ligase

June 2012: Describe the role of each mRNA and tRNA in protein synthesis.mRNA: Idea of mRNA being a copy of the antisense DNA strand / template DNA strand / coding DNA strand / gene / allele / part of DNA Idea that mRNA made up of codons / codes for specific amino acids / code for amino acid sequence Idea of mRNA being taken into the cytoplasm / to the ribosomes / out of the nucleus Used in translation Binds to ribosometRNA: tRNA attaches to / transports specific amino acid Idea that tRNA binds to mRNA / reference to anticodon codon interaction Idea that two tRNA bring amino acids together for peptide bonds to be formed

January 2013: Messenger RNA (mRNA) and transfer RNA (tRNA) are important nucleic acids involved in the process of protein synthesis. Describe how a molecule of mRNA is made during transcription. Idea that DNA molecule unwinds / unzips / uncoils / DNA strands separate Free RNA mono nucleotides line up against / attach to one strand / template / antisense strand Ref to complementary base pairing between DNA and mononucleotides Ref to formation of phosphodiester bonds Ref to condensation reaction Correct name of enzyme involved Idea that mRNA detaches from the DNA

January 2013: Describe two ways in which the structure of a tRNA molecule differs from the structure of a mRNA molecule. tRNA is folded and mRNA is straight / unfolded tRNA has hydrogen bonds holding the structure together but the mRNA does not tRNA is a fixed size / length but mRNA is not / length depends on size of gene tRNA has an anticodon but mRNA has codons tRNA has an amino acid binding site

Explain the nature of the genetic code (12).

Describe a gene as being a sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain. (13)

Outline the process of protein synthesis, including the role of transcription, translation, messenger RNA, transfer RNA and the template (antisense) DNA strand (details of the mechanism of protein synthesis on ribosomes are not required at AS). (14)

January 2010: Read through the following passage on protein synthesis, on the dotted lines the most appropriate word or words have been added to complete the passage. Protein synthesis involves two stages. The first stage is ..................transcription................ and takes place in the nucleus of the cell. During this stage, a molecule called ...........................mRNA............................ is made using the antisense DNA strand as a template.The second stage, known as .............................translation............... , takes place in the cytoplasm of the cell on structures called ..................................ribosomes........................ . During this stage,.tRNA......................... molecules enable the amino acids attached to them to line up in the correct order. The amino acids are joined together by the formation of................................peptide.................... bonds.

June 2011: The sequence of amino acids in a polypeptide chain is determined by the sequence of bases in DNA. This sequence of bases is used as a template to synthesise messenger RNA (mRNA). Describe how mRNA is synthesised. Correct reference to transcription DNA unwinds / strands separate RNA mononucleotides line up against / attach to one DNA strand / template Reference to complementary base pairing between DNA and mono nucleotides Reference to mononucleotides joining together / formation of phosphodiester bonds Correct reference to condensation reaction Correct reference to named enzymes involved mRNA detaches from DNA

Explain how errors in DNA replication can give rise to mutations and explain how cystic fibrosis results from one of a number of possible gene mutations. (15)

January 2011: Thalassaemia is the name of a group of inherited blood disorders that affect the bodys ability to produce haemoglobin in red blood cells. Red blood cells are produced in bone marrow. Oxygen in the lungs binds to haemoglobin and is carried to the cells of the body to be used in respiration.Beta thalassaemia is the result of a mutation in the gene coding for the chain of haemoglobin. If a person inherits gene mutations from both parents, this person will show symptoms of anaemia and will require blood transfusions. Symptoms of anaemia include tiredness and breathlessness. Using the information given above and your knowledge of gene mutation, suggest why a person with beta thalassaemia has symptoms of anaemia. Idea of mutation / named mutation causing different base sequence Reference to different sequence of amino acids / primary structure. Reference to chain / haemoglobin / protein / polypeptide being the wrong shape. Haemoglobin no longer binds oxygen / binds less oxygen. Less / no oxygen supplied / carried to the cells. Correct reference to respiration. Idea of breathlessness due to body trying to take in more oxygen. Idea of tiredness due to lack of energy

Explain the terms gene, allele, genotype, phenotype, recessive, dominant, homozygote and heterozygote, and explain monohybrid inheritance, including the interpretation of genetic pedigree diagrams, in the context of traits such as cystic fibrosis, albinism, thalassaemia, garden pea height and seed morphology.(16)

June 2009: Distinguish between the terms allele and gene.An allele is the different form/versions of a gene.A gene is a section of DNA / sequence of bases that codes for a polypeptide / occupies a particular locus on a chromosome.

June 2009: Explain the meaning of the term recessive allele.A recessive allele is an allele that is only expressed (in the phenotype of an organism) if the dominant allele is not present.

June 2009: Explain the meaning of the term homozygous.Homozygous is alleles of a particular gene that are the same.

June 2009: Suggest why the incidence of albinism in squirrels is lower than the incidence in humans, giving a reason for your answer. Idea that fewer albino squirrels survive/ squirrels may not breed so frequently. A suitable reason given (e.g.more predation, less camouflage) Idea of frequency of albinism allele in squirrel (population) is lower / chances of two squirrels with the allele less likely to mate. Comment on the lower mutation rate(in squirrels).

January 2010: Using your knowledge of monohybrid crosses, calculate the probability of having a child with cystic fibrosis if both partners are found to be carriers. Draw a genetic diagram to explain how you calculated this probability. Heterozygous genotype of both parents shown or stated Possible alleles carried in the gametes shown (can be shown in a Punnet square) Possible genotypes of offspring clearly shown (can be shown in a Punnet square) Corresponding phenotypes given Probability of having child with cystic fibrosis's 25% / 1in4 / 14 / 0.25

June 2011: An allele is a: Form of a gene

January 2012: Explain the meaning of the term genotype:The alleles present in an organismJanuary 2012: Explain the meaning of the term allele:A different form of one gene

June 2012: Explain the meaning of each of these terms: mutation and recessive.Mutation: Reference to alteration in DNA Change in base sequence / quantity of DNARecessive: Idea that both of these alleles need to be present in order for the recessive phenotype to be expressed

January 2013: Cystic fibrosis and albinism are examples of recessive genetic disorders. Tay-Sachs disease is another example of a recessive genetic disorder. Explain the meaning of the term recessive genetic disorder.Recessive genetic disorder: The disorder results from a defect in genes (ALLOW faulty allele) Both defective alleles need to be present / homozygous / not expressed in the presence of a dominant allele

Explain how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems.(17)

June 2010: Cystic fibrosis is a genetic disease that can affect many body systems, including the respiratory system. Explain how a gene mutation causes a build up of mucus in the respiratory system of a person with cystic fibrosis. Reference to CFTR protein / channel Reference to a different amino acid / sequence of amino acids on the defective CFTR protein Reference to change in protein Reference to role of protein in transporting chloride ions Reference to chloride ions not moving out of cells / going into mucus. Reference to sodium ions moving in to the cells / mucus Water does not move out of cells / water moves in to cells By osmosis Mucus on cell surface is not diluted/ becomes thicker / becomes stickier Thickened mucus cannot be moved by cilia / coughing

June 2010: Suggest why people with cystic fibrosis are more likely to suffer from lung infections than people without cystic fibrosis. Idea that mucus traps bacteria / pathogens Idea that bacteria / mucus containing the bacteria cannot be removed by cilia Idea that mucus provides conditions for bacteria to live / grow / develop Reference to antibodies not being effective Reference to trauma caused by coughing Idea that resident phagocytes/ macrophages cannot destroy bacteria

June 2011: Cystic fibrosis is a genetic disease that can affect many body systems, including the digestive system. In a carrier of this disorder, preimplantation genetic diagnosis can be used to detect the presence of an allele for cystic fibrosis. Explain how cystic fibrosis affects the digestive system. Reference to CFTR gene / channel not functioning properly Reference to thicker / stickier mucus Mucus blocks pancreatic duct(s) In the pancreas Idea that enzymes cannot be secreted Into / reach small intestine Idea of reduced digestion of food / named food Reference to reduced absorption Idea of malnutrition / weight loss Idea of self-digestion of pancreatic cells / problems controlling blood sugar levels / cysts / fibroids

June 2012: Cystic fibrosis and albinism are examples of recessive genetic disorders.Krabbe disease is another example of a recessive genetic disorder.Krabbe disease is caused by mutations in the GALC gene, resulting in a deficiency of an enzyme called galactocerebrosidase. Suggest how a mutation in the GALC gene could result in a change in the enzyme galactocerebrosidase. Idea of a gene being a sequence of bases that code for the sequence of amino acids in the protein / polypeptide chain / enzyme / galactocerebrosidase Gene mutation will alter DNA triplet / DNA code / codon This may result in a different amino acid / stop codon / amino acid sequence / primary structure Idea that this may change the shape of protein / enzyme Therefore causing no synthesis / incomplete of enzyme / galactocerebrosidase / change of active site

Describe the principles of gene therapy and distinguish between somatic and germ line therapy.(18)

June 2010: Cancer can cause a lot of pain. Pain can be reduced by a chemical called endorphin that is made by cells in the brain and spinal cord. Endorphin reduces the activity of neurones that carry impulses from pain receptors.Gene therapy has been used in rats to increase the tolerance to pain.Viruses, containing a gene coding for endorphin, were developed. These viruses were injected into the spinal cords of a group of rats. The level of tolerance to pain was tested in these rats and in the rats in a control group. Describe the role of the viruses in this investigation. Reference to virus acting as a vector Idea that virus is used to get the (usually functioning) gene/DNA into the cellsSuggest why the injection was made into the spinal cord. Reference to neurones in spinal cord Endorphins being made in spinal cord spinal cord connects to brain Suggest why a gene coding for an endorphin was used in this investigation. Idea that endorphins have pain-reducing properties More endorphins Endorphin secreting cells produced

January 2011: Thalassaemia is the name of a group of inherited blood disorders that affect the bodys ability to produce haemoglobin in red blood cells. Red blood cells are produced in bone marrow.Oxygen in the lungs binds to haemoglobin and is carried to the cells of the body to be used in respiration. Beta thalassaemia is the result of a mutation in the gene coding for the chain of haemoglobin. If a person inherits gene mutations from both parents, this person will show symptoms of anaemia and will require blood transfusions. Symptoms of anaemia include tiredness and breathlessness.Gene therapy could potentially be used to treat beta thalassaemia.Suggest how gene therapy could be carried out to treat this disorder. Reference to use of normal / correct allele / gene For haemoglobin / chain Reference to introduction of gene / allele / DNA into cells. Cells named as bone marrow Reference to use of vector to introduce gene into cells Named vector e.g.virus,liposome. Credit reference to appropriate mode of delivery of vector e.g. injection into (bone) marrow. Reference to need for repeated treatment.

January 2012: Gene therapy has the potential to treat some genetic disorders. Explain why gene therapy has the potential to treat some genetic disorders. Reference to faulty alleles / genes / DNA Idea that gene therapy uses normal / functioning / healthy alleles / genes So the normal protein / gene product / RNA is produced by the cells

January 2012: Suggest how patients with cystic fibrosis could be treated using gene therapy. Reference to using alleles / genes coding for the CFTR protein / channel Reference to introducing the alleles / genes into the cells Of the lungs / pancreas / reproductive tracts That produce mucus Using a vector / named vector Credit suitable delivery mechanism e.g. nebuliser, injection Idea that treatment needs to be repeated due to cell replacement

January 2013: Tay-Sachs disease is caused by a gene mutation that results in the build up of lipid in the brain. It is hoped that gene therapy will be able to treat this disease in the future.Sheep can also suffer from Tay-Sachs disease. Investigations have found that gene therapy increases the life span of these animals. Suggest how these gene therapy investigations could have been carried out. Isolation / identification of normal gene Inserted into vector / stem cells Vector named as liposome / virus Injection of vector / modified stem cells} into {blood / brain / target cells Ref to use of control injection Further detail of control injection e.g. use empty liposome / virus without gene inserted Progression of disease monitored Life spans recorded Reference to appropriate Comparison with control e.g. untreated sheep Idea that treatment needs to be repeated Idea of replication of investigation

Explain the uses of genetic screening: identification of carriers, preimplantation genetic diagnosis and prenatal testing (amniocentesis and chorionic villus sampling) and discuss the implications of prenatal genetic screening.(19)

June 2009: Name one method of prenatal testing and explain how it can be used to detect cystic fibrosis:Amniocentesis: amniotic fluid removed from amniotic sac of mother. Fetal /embryonic cells present in amniotic fluid /fetal / embryonic cells needed DNA can be analysed To detect defective gene(s) in sampleORChorionic villus sampling: placental tissue removed from womb of mother fetal cells present in placenta/placental tissue / chorionic tissue / fetal cells needed DNA can be analysed to detect defective gene(s) in sample

June 2009: Describe one benefit and one risk, to a pregnant woman, of prenatal testing:Benefit: Gives information about abnormalities (in fetus). Opportunity for choice consider termination / time for preparation / treatment / peace of mind

Risk: Possibility of miscarriage due to procedure. Potentially a healthy baby would be lost risk to mother

OR Idea of false positive / false negative result Wrong decision made / description of wrong decisionOR Damage / harm to fetus Subsequent health issues / miscarriages

January 2010: Cystic fibrosis is a life-threatening condition that can affect many different parts of the body. It is a recessive genetic trait. Genetic screening can be used to test for the presence of recessive alleles. A person found to possess a recessive allele is called a carrier. Suggest why cells from mouth swabs or blood samples are used rather than gametes. Idea that at these cells are easy/painless to collect Idea that a relatively large amount of DNA / large number of cells can be collected They contain diploid cells / have 23 pairs of chromosomes Cells are genetically identical / have same DNA / have same alleles Any recessive allele / mutated CF gene will be present in them Idea that if the gametes were tested they may not contain the recessive allele / mutated CF gene as they are haploid

January 2010: Explain why it is necessary to test for several different recessive alleles in the screening for cystic fibrosis. Cystic fibrosis results from one of a number of possible mutations of this gene Idea that testing for only one will miss other recessive alleles

January 2010: If neither partner is a carrier then it is considered that the chance of having a child with cystic fibrosis is low. Explain why the probability of having a child with cystic fibrosis is low and not zero. Ref to false negatives Idea that the screening programme does not test for all the possible mutations that can cause cystic fibrosis Idea that a mutation may occur in the formation of the gametes Idea of mutation in both gametes Idea that a mutation may occur after fertilisation

January 2010: If one of the partners is found to be a carrier then screening for cystic fibrosis may be offered to other family members. Explain why this screening is offered to other family members. Idea that any other family member could be a carrier Idea that in formed choices can be made about having children if they know that they are carriers

June 2011: Explain how preimplantation genetic diagnosis is performed to detect cystic fibrosis. Reference to IVF / description of preimplantation Embryo DNA analysed Presence of CFTR gene mutation / faulty allele tested for

January 2012: Name one method of prenatal genetic screening: Amniocentesis Chorionic villus sampling

Identify and discuss the social and ethical issues related to genetic screening from a range of ethical viewpoints.(20)

June 2009: Discuss either one ethical issue or one social issue relating to the use of prenatal testing: Idea that a fetus is living Abortion is wrong / murder Who has right to decide if tests should be performed Implications of medical costs / disagreements over next step Issues relating to confidentiality of parents/ child Idea that some other abnormality may be found / paternal DNA does not match / other family members have right to know results Some other abnormality may be found Comment on possible problems with future employment / insurance / what constitutes a serious condition Not fully understanding possible risks of prenatal testing Possibility of miscarriage/harm to child Who has the right to make the decision for the fetus / fetus has decision rights if the test is positive Denying them the opportunity to live / fetus should be allowed to live / fetus has a right to live

June 2011: Discuss either one ethical issue or one social issue relating to the use of preimplantation genetic diagnosis.Any of the following paired points: Who has right to decide if tests should be performed Implications of medical costs / disagreements over next step / embryo has rightsOR Issues relating to confidentiality of parents / child Idea that some other abnormality may be found / paternal DNA does not match / other family members have right to know results.OR Idea some other abnormality may be found/ false negative Comment on possible problems with e.g. future employment / insurance / what constitutes a serious condition.OR Idea that embryo could be damaged / destroyed / discarded / false positive Embryo is a potential life / has rights / destroying embryo is wrong / unethical / murder

January 2012: Discuss either one ethical issue or one social issue relating to the use of either amniocentesis or chronic villus sampling of prenatal genetic screening. Idea of right to life Abortion is murder / ref to risk of miscarriage Or: False positive / negative Consequences of false result e.g. abortion of healthy fetusOr: Who has right to decide if tests should be performed Implications of medical costs / discrepancies over next step} / parents have a right to know / can prepare Or: Issues relating to confidentiality of parents / child Idea that some other abnormality may be found / paternal DNA does NOT match / other family members have right to know resultsOr: If abnormality found Consequence of abnormality found e.g. abortion, comment on possible problems with future employment / insurance / what constitutes a serious conditionOr: Damage to fetus / risk of miscarriage loss of fetus / risk to mother Or: Ref. to stress to parents Consequences of stress e.g. increased risk of miscarriage