Human Biology HBIO4. (JUN14HBIO401) WMP/Jun14/HBIO4/E7w. General Certificate of Education Advanced Level Examination June 2014

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1 Centre Number Surname Candidate Number For Examiner s Use Other Names Candidate Signature Examiner s Initials Human Biology Unit 4 Friday 13 June 2014 For this paper you must have: l a ruler with millimetre measurements l a calculator. Time allowed l 2 hours General Certificate of Education Advanced Level Examination June 2014 Bodies and cells in and out of control 1.30 pm to 3.30 pm HBIO4 Question TOTAL Mark Instructions l Use black ink or black ball-point pen. l Fill in the es at the top of this page. l Answer all questions. l You must answer the questions in the spaces provided. around each page or on blank pages. l Do all rough work in this book. Cross through any work you do not want to be marked. Information l The marks for questions are shown in brackets. l The maximum mark for this paper is 90. l You are expected to use a calculator where appropriate. l You will be marked on your ability to: use good English organise information clearly use scientific terminology accurately. (JUN14HBIO401) /E7w HBIO4

2 2 Answer all questions in the spaces provided. 1 Figure 1 shows spermatogenesis. Letters A to H label individual cells. Numbers 1, 2 and 3 show where cell divisions occur. Figure 1 A Cell divisions + Growth 1 B 2 C D 3 E F G H Sperm (02)

3 3 1 (a) Numbers 1, 2 and 3 show where cell divisions occur. Give one number which represents mitosis. [1 mark] 1 (b) (i) Cells C and D are genetically different. Give the letters of two cells which are genetically identical. and [1 mark] 1 (b) (ii) Give two processes, which occur in cell B, that cause cells C and D to be genetically different. [2 marks] Turn over for the next question Turn over (03)

4 4 2 (a) Describe the trichromatic theory of colour vision. [2 marks] 2 (b) A person noticed a faint star in the night sky. When the person looked directly at the star, it disappeared. When the person looked slightly to one side of the star s position, it reappeared. 2 (b) (i) Explain why the star disappeared when looking straight at it. [2 marks] 2 (b) (ii) Explain why the star reappeared when looking slightly to one side of it. [2 marks] 6 (04)

5 5 3 (a) Describe the effect of calcium ions on tropomyosin and actin in skeletal muscle. [2 marks] 3 (b) Describe the roles of ATP, actin and myosin in muscle contraction. [4 marks] [Extra space]... 6 Turn over (05)

6 6 4 Table 1 gives the mrna codons for six different amino acids. Table 1 Amino acid mrna codons Ala GCU GCC GCA GCG Gly GGU GGC GGA GGG Phe UUU UUC Pro CCU CCC CCA CCG Ser UCU UCC UCA UCG AGU AGC Thr ACU ACC ACA ACG A section of DNA contained the sequence of bases given in Table 2. Table 2 DNA bases C C A C G T A A G T G G C C G mrna bases Amino acids (06)

7 7 4 (a) (i) Complete Table 2 to show the sequence of bases in the mrna transcribed from this section of DNA. [1 mark] 4 (a) (ii) Use information from Table 1 to complete the sequence of amino acids coded for by this section of DNA in Table 2. [1 mark] 4 (b) (i) A substitution mutation occurred in this section of DNA. The base T, in the grey, was replaced by the base C. Explain why this had no effect on the sequence of amino acids. [2 marks] 4 (b) (ii) A deletion mutation occurred in which the base T, in the grey, was lost from the DNA. What effect would this deletion have on the sequence of amino acids? [1 mark] 5 Turn over for the next question Turn over (07)

8 8 5 Scientists investigated the role of the hypothalamus in temperature regulation. The scientists cooled and then warmed the hypothalamus in a small mammal. At the same time they measured changes in the temperature of the hypothalamus, in metabolic rate and in body temperature. The results are shown in Figure 2. Figure 2 Cooled Warmed Cooled Warmed Temperature of hypothalamus / C Metabolic rate / kj kg 1 h Basal metabolic rate Body temperature / C Time / hours (08)

9 9 5 (a) (i) In order to estimate the metabolic rate of the small mammal, the scientists measured its rate of oxygen consumption. Suggest why. [1 mark] 5 (a) (ii) Figure 2 shows a value for basal metabolic rate. What is basal metabolic rate? [1 mark] 5 (a) (iii) What evidence in Figure 2 suggests that the hypothalamus regulates body temperature? [2 marks] Question 5 continues on the next page Turn over (09)

10 10 5 (b) A second group of scientists investigated the effect of temperature on two types of neurone in the hypothalamus, Type A and Type B. The scientists measured the rate of production of impulses in each type of neurone at two different temperatures. Figure 3 shows the results. Each vertical line represents an action potential. Response at 32 C Figure 3 Type A neurone Type B neurone 0 0 Membrane potential / mv 40 Membrane potential / mv Time / ms Time / ms Response at 39 C Type A neurone Type B neurone 0 0 Membrane potential / mv 40 Membrane potential / mv Time / ms Time / ms (10)

11 11 5 (b) (i) For each type of neurone, what is the ratio of the rate of action potential production when the temperature is raised from 32 C to 39 C? [2 marks] Type A Rate at 39 C : Rate at 32 C =... : 1 Type B Rate at 39 C : Rate at 32 C =... : 1 5 (b) (ii) The scientists described the two types of neurones as being either warm-sensitive or temperature-insensitive. Which type of sensitivity does neurone Type B have? Give evidence for your answer. [1 mark] 5 (b) (iii) When the hypothalamus is warmed, receptors are stimulated. This leads to nerve impulses being sent along motor neurones to effectors. [1 mark] Name one of these effectors... Describe the response produced by this effector. 8 Turn over for the next question Turn over (11)

12 12 6 People with type 2 diabetes have higher concentrations of glucose in their blood after a meal than non-diabetic people. Doctors investigated the effect of taking glucose by mouth compared with injecting the same mass of glucose directly into the blood. The doctors: l l investigated type 2 diabetic people and non-diabetic people monitored the concentration of insulin in the blood for three hours following the intake of glucose. Table 3 shows the results with the non-diabetic people. Table 3 Non-diabetic people Glucose taken by mouth Glucose injected into the blood Maximum concentration of insulin in the blood / milliunits dm Time taken to reach maximum insulin concentration in the blood / minutes The doctors suggested that: l l l glucose taken by mouth caused the release of a hormone from the gut this hormone stimulated the pancreas to secrete insulin the hormone was more important than glucose itself in stimulating the secretion of insulin from the pancreas. 6 (a) Explain how the data in Table 3 support the doctors suggestions. [3 marks] [Extra space]... (12)

13 13 6 (b) Table 4 shows the results with the type 2 diabetic people. Table 4 Type 2 diabetic people Glucose taken by mouth Glucose injected into the blood Maximum concentration of insulin in the blood / milliunits dm Time taken to reach maximum insulin concentration in the blood / minutes The doctors suggested two hypotheses to explain the difference in results between the type 2 diabetic people and the non-diabetic people. Hypothesis 1: Less hormone is released from the gut of type 2 diabetic people in response to glucose than is released from the gut of non-diabetic people. Hypothesis 2: Pancreas cells are less sensitive to the gut hormone in type 2 diabetic people compared with pancreas cells in non-diabetic people. The doctors were able to purify the gut hormone and use it to test their hypothesis. They injected the same amount of the purified gut hormone into the blood of type 2 diabetic people and of non-diabetic people. For each hypothesis, what pattern of results would you expect for the diabetic people compared with the non-diabetic people? [3 marks] Hypothesis 1... Hypothesis Turn over (13)

14 14 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED (14)

15 15 7 Voltage-gated ion channels are found in the surface membranes of neurones. 7 (a) Voltage-gated sodium ion channels help to generate an action potential. Explain how. [3 marks] [Extra space]... 7 (b) When a neurone is transmitting a series of action potentials, the neurone s rate of oxygen consumption is higher than when it is at rest. Explain why. [3 marks] [Extra space]... Turn over (15)

16 16 7 (c) Tetrodotoxin (TTX) is a toxin that causes muscle paralysis. Scientists recorded the amount of acetylcholine released by neurones in two samples of nerve tissue, A and B. Both samples were kept in sodium chloride solution. After 30 minutes, TTX was added to sample B only. At 90 minutes, they used sodium chloride solution to wash away the TTX. Figure 4 shows their results. Figure TTX added (Sample B only) Amount of acetylcholine released / percentage of starting value Time / minutes Key A = sodium chloride solution B = sodium chloride solution + TTX (16)

17 17 TTX binds to sodium ion channels in neurone membranes and prevents them from opening. Use information from Figure 4 to explain how TTX causes muscle paralysis. [3 marks] [Extra space]... 9 Turn over for the next question Turn over (17)

18 18 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED (18)

19 19 8 (a) What is cancer? [1 mark] 8 (b) Exemestane is a drug that is used to inhibit an enzyme in the fatty tissue of some women with breast cancer. The enzyme catalyses the reaction: androgens enzyme oestrogen Explain how exemestane helps to slow the growth of breast cancer. [2 marks] Question 8 continues on the next page Turn over (19)

20 20 8 (c) With time, advanced breast cancer may become resistant to treatment with exemestane and so may start to grow again. Doctors have investigated the use of a new drug, called everolimus, for the treatment of advanced breast cancer. 724 post-menopausal women took part in the investigation. Each woman had advanced breast cancer. The doctors gave two-thirds of the women both exemestane and everolimus. They gave one-third of the women exemestane and a placebo. Figure 5 shows the results. Figure Percentage of women surviving Exemestane + everolimus 20 Exemestane + placebo Time after start of treatment / months 8 (c) (i) From Figure 5, use the figures for 50% survival to calculate how many extra months survival occurred, on average, using everolimus. Show your working. [2 marks] Answer =... months (20)

21 21 8 (c) (ii) Everolimus inhibits an enzyme called mtor. This enzyme normally stimulates the cell to enter the DNA-synthesis stage of the cell cycle. Suggest how treatment with everolimus can inhibit the growth of breast cancers. [2 marks] 8 (c) (iii) In the group taking everolimus: l l cancerous growths reduced in size by over 30% in 12 percent of women 27 percent of women dropped out because of side effects. Treatment with everolimus costs 2935 per month. Using all of the information, evaluate the use of everolimus in the treatment of breast cancer. [3 marks] [Extra space] Turn over (21)

22 22 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED (22)

23 23 9 Omega-3 and omega-6 are two types of unsaturated fatty acids. Doctors think that a diet with a high omega-3:omega-6 fatty acid ratio is better for health. Scientists are trying to produce meat from pigs that contains a higher concentration of omega-3 fatty acids. Three different approaches are being used: l l l selective breeding adding fishmeal to pigs diets genetic engineering. 9 (a) (i) Suggest how selective breeding might be used to increase the proportion of omega-3 in pigs. [2 marks] 9 (a) (ii) Feeding pigs with omega-3-rich fishmeal may not affect the ratio of omega-3:omega-6 fatty acids in their meat. Suggest why. [1 mark] Question 9 continues on the next page Turn over (23)

24 24 9 (b) Scientists have produced genetically-engineered pigs containing a gene from a worm. This gene codes for an enzyme that converts omega-6 fatty acids into omega-3 fatty acids. Figure 6 shows the method used to produce the genetically-engineered pigs. Figure 6 mrna from worm gene Step 1 Reverse transcriptase DNA from worm gene Step 2 DNA of gene giving resistance to antibiotic Worm DNA joined to antibiotic-resistance DNA Step 3 Mix with cells from pig Add antibiotic that normally kills cells of pig Only cells containing worm gene Step 4 Cells used to make pig embryos 9 (b) (i) Give two advantages of using mrna to make the worm gene at step 1, rather than using a restriction enzyme to cut the gene from the worm s DNA. [2 marks] (24)

25 25 9 (b) (ii) Explain why a gene giving resistance to an antibiotic is attached to the DNA at step 2. [2 marks] 9 (b) (iii) Scientists produced 1633 pig embryos using this method. From these, only 12 piglets were born and only 6 of these contained the worm gene. Half of these piglets died of heart failure within a few days. Muscle cells from one of the surviving piglets were used to clone 8 more healthy piglets, as in step 4 of the diagram. Meat from these cloned piglets contained 3 times the amount of omega-3 fatty acids and only 23% of the amount of omega-6 fatty acids found in the meat from normal pigs. A representative of an animal rights group condemned this investigation as being unethical. Do you agree with this conclusion? Give reasons for your answer. [4 marks] [Extra space] Turn over (25)

26 26 10 (a) Figure 7 shows changes in the blood concentrations of four hormones during one menstrual cycle. Figure 7 Concentration / arbitrary units FSH Oestrogen LH Progesterone Time / days 10 (a) (i) On what day did ovulation occur in this cycle? 10 (a) (ii) Describe and explain two pieces of evidence for your answer to part (a)(i). [1 mark] [4 marks] (26)

27 27 10 (b) Duchenne muscular dystrophy (DMD) is a sex-linked condition. It is caused by a recessive allele on the X chromosome. Mr Jones is unaffected by DMD. Mrs Jones is a carrier of DMD. 10 (b) (i) Complete the genetic diagram to find the probability that Mr and Mrs Jones next child will have muscular dystrophy. Use the following symbols: X D = normal X chromosome X d = X chromosome carrying the allele for DMD Y = normal Y chromosome Mr Jones Mrs Jones [4 marks] Parental phenotypes Unaffected Unaffected Parental genotypes Genotypes of gametes Offspring genotypes... Offspring phenotypes Probability of having a child with DMD... Turn over (27)

28 28 10 (b) (ii) Mr and Mrs Jones wanted to have a child that would not have DMD. They decided to use IVF followed by pre-implantation genetic screening (PGS) to select the sex of the embryo. Describe the process of IVF. [5 marks] [Extra space] (b) (iii) In Mr and Mrs Jones case, it was important to carry out PGS to select the sex of the embryo. Explain why. [1 mark] (28)

29 29 10 (c) Following the birth of the child, Mrs Jones decided to use an oral contraceptive pill. Scientists have investigated the effect on follicle development of two drugs used in oral contraceptive pills. The drugs were desogestrel (DE) and levonorgestrel (LE). The scientists recruited two groups of women volunteers, D and L. l l Group D took a pill containing DE each day for one year. Group L took a pill containing LE each day for one year. The scientists measured the diameters of the follicles developing in the ovaries of each woman during each menstrual cycle using an ultrasound scan. They also recorded the highest concentrations of progesterone, FSH and LH in blood samples. 10 (c) (i) None of the women had used a hormone-based oral contraceptive before the investigation. Why was this important? [1 mark] 10 (c) (ii) All the women were between 20 and 38 years of age. The mean age of the women in each group was the same. Suggest two other variables that should have been controlled in this investigation. [2 marks] Turn over (29)

30 30 10 (c) (iii) Tables 5, 6 and 7 show the scientists results. Table 5 Condition of follicles after 12 menstrual cycles Number of women in each group DE LE No change in diameter 9 3 Diameter increased to 15 30mm Diameter increased to > 30 mm Follicle burst 1 10 Table 6 Concentration of progesterone after 12 menstrual cycles / arbitrary units Number of women in each group DE LE < > Table 7 Hormone Median value of the peak concentration of FSH and LH in each cycle / arbitrary units At start After 12 menstrual cycles DE LE DE LE FSH LH (30)

31 31 The scientists performed a statistical test to compare the effects of DE and LE on the LH concentrations. The test results gave a probability, p< Explain what this means. [2 marks] 10 (c) (iv) The scientists concluded that DE was more reliable than LE as a contraceptive agent. Evaluate this conclusion. Use the information given about this investigation. [5 marks] END OF QUESTIONS 25 (31)

32 32 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED ACKNOWLEDGEMENT OF COPYRIGHT-HOLDERS AND PUBLISHERS Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright-holders have been unsuccessful and AQA will be happy to rectify any omissions of acknowledgements in future papers if notified. Copyright 2014 AQA and its licensors. All rights reserved. (32)

Human Biology HBIO4. General Certificate of Education Advanced Level Examination January Unit 4 Bodies and cells in and out of control

Human Biology HBIO4. General Certificate of Education Advanced Level Examination January Unit 4 Bodies and cells in and out of control Centre Number Surname Candidate Number For Examiner s Use Other Names Candidate Signature Examiner s Initials General Certificate of Education Advanced Level Examination January 2012 Question 1 2 Mark