9700_w08_qp_4
A paper of Biology, 9700
Questions:
11
Year:
2008
Paper:
4
Variant:
0
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1
The African hunting dog, Lycaon pictus, is a carnivore which hunts in packs in areas of East Africa. shows an African hunting dog. The African hunting dog has cells that are eukaryotic while bacteria have cells that are prokaryotic. Describe the differences between eukaryotic and prokaryotic cells with respect to their DNA. For Examiner’s Use In some parts of East Africa L. pictus is becoming an endangered species. Suggest reasons why L. pictus is becoming an endangered species. One way of protecting L. pictus is to create conservation areas. Describe two other methods of conserving endangered species such as L. pictus.
18. Classification, biodiversity and conservation  →  18.3. Conservation
17. Selection and evolution  →  17.3. Evolution
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2
For Examiner’s Use shows the CFTR (cystic fibrosis transmembrane conductance regulator) protein in a plasma (cell surface) membrane. Describe the normal function of the CFTR protein. On , use the letter E to indicate the external face of the membrane. State how you identified this face. Cystic fibrosis is caused by a recessive allele of the CFTR gene. Explain the meaning of the term recessive allele. For Examiner’s Use Explain how cystic fibrosis affects the function of the lungs. As cystic fibrosis is caused by a recessive allele of a single gene, it is a good candidate for gene therapy. Trials were undertaken in the 1990s, attempting to deliver the normal allele of the CFTR gene into cells of the respiratory tract, using viruses or liposomes as vectors. Explain how viruses deliver the allele into cells. For Examiner’s Use In some people with cystic fibrosis, the allele has a single-base mutation which produces a ‘nonsense’ codon within the gene. Explain how this mutation would prevent normal CFTR protein being produced. A new type of drug, PTC124, enables translation to continue through the nonsense codon. Trials in mice homozygous for a CFTR allele containing the nonsense codon have found that animals treated with PTC124 produce normal CFTR protein in their cells. The drug is taken orally, and is readily taken up into cells all over the body. Using your knowledge of the progress towards successful gene therapy for cystic fibrosis, suggest why PTC124 could be a simpler and more reliable treatment for this disease.
19. Genetic technology  →  19.2. Genetic technology applied to medicine
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
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3
For Examiner’s Use Sorghum is a cereal crop that grows well in very dry conditions. Outline two structural features of sorghum that adapt it to survive in arid environments. An investigation was carried out to measure the effect of lack of water on the leaves of sorghum plants. • Several well-watered sorghum plants were kept in conditions of normal light and temperature. • Watering was then stopped for 6 days, and resumed on day 7. • The water potential of the cells in the leaves, the concentrations of abscisic acid in the leaves and stomatal resistance were measured each day. A high stomatal resistance indicates that most stomata are partially or completely closed. The results are shown in . –1600 –1200 –800 –400 time / days watering stopped watering resumed mean concentration of abscisic acid / ngcm–2 mean stomatal resistance / arbitrary units mean leaf water potential / kPa For Examiner’s Use With reference to , describe and explain the changes in abscisic acid concentration over the 10 day period explain the changes in stomatal resistance over this period. Explain how the changes you have described in help sorghum to survive in arid conditions.
14. Homeostasis  →  14.2. Homeostasis in plants
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4
For Examiner’s Use Outline the hybridoma method for the production of a monoclonal antibody. Herceptin is a monoclonal antibody used in the treatment of some breast cancers. It binds strongly to molecules of a receptor protein, HER2, that is produced in abnormally large quantities in the plasma (cell surface) membranes of about 30% of human breast cancers. Investigations have been made into the most effective way to use Herceptin to treat breast cancer. One experiment investigated the ability of different treatments to induce cell death in breast cancer cells. Herceptin and X-ray treatment were used both separately and together. The results are shown in . 1.0 2.0 ability to induce cell death / arbitrary units no treatment Herceptin only X-ray treatment only Herceptin and X-ray treatment For Examiner’s Use With reference to , compare the effects on breast cancer cells of the different treatments calculate the percentage increase in the ability to induce cell death of using Herceptin and X-ray treatment compared with using Herceptin only. Show your working. For Examiner’s Use A second experiment investigated the effect of increasing doses of X-rays on the survival of breast cancer cells in the presence and absence of Herceptin. The results are shown in . 1.0 10.0 mean percentage of cells surviving (log scale) absorbed dose of X-rays / J kg–1 X-rays and Herceptin X-rays With reference to , compare the effects of increasing doses of X-rays on cells in the presence and absence of Herceptin suggest an explanation for the effect of Herceptin.
11. Immunity  →  11.2. Antibodies and vaccination
19. Genetic technology  →  19.2. Genetic technology applied to medicine
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5
For Examiner’s Use Complete Table 5.1 to show, for each of the two hormones, follicle stimulating hormone (FSH) and progesterone, • the site of secretion • the target tissue• the action of the hormone during the human menstrual cycle. Table 5.1 hormone site of secretion target tissueaction during human menstrual cycle FSH progesterone Explain the biological basis of the oestrogen/progesterone contraceptive pill.
15. Control and coordination  →  15.1. Control and coordination in mammals
14. Homeostasis  →  14.1. Homeostasis in mammals
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6
For Examiner’s Use shows the structure of ATP. NH2 CH2 N N N H H H H OH N OH O P P P B S Name the nitrogenous base labelled B. Name the sugar labelled S. ATP is described as having a universal role as the energy currency in all living organisms. Explain why it is described in this way. For Examiner’s Use State precisely two places where ATP is synthesised in cells.
12. Energy and respiration  →  12.1. Energy
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
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7
For Examiner’s Use shows a section through part of the cortex of a kidney. On , draw label lines and use the letters G and R to identify : • a glomerulus with the letter G. • a renal capsule with the letter R. State the name of the hormone that is involved in the control of the water potential of the blood. For Examiner’s Use Table 7.1 shows the concentration of some compounds in the fluids of a glomerulus, a renal capsule and a collecting duct of the kidney. Table 7.1 compound concentration / g 100 cm–3 blood plasma entering glomerulus filtrate in renal capsule urine in collecting duct water proteins 8.0 0.0 0.0 glucose 0.1 0.1 0.0 urea 0.03 0.03 2.0 With reference to Table 7.1, explain why proteins occur in the blood entering the glomerulus but not in the filtrate in the renal capsule explain why there is glucose present in the filtrate but not in the urine explain the difference in the concentration of urea between the filtrate and urine.
14. Homeostasis  →  14.1. Homeostasis in mammals
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8
For Examiner’s Use In mice there are several alleles of the gene that controls the intensity of pigmentation of the fur. The alleles are listed below in order of dominance with C as the most dominant. C = full colour Cch = chinchilla Ch = himalayan Cp = platinum Ca = albino The gene for eye colour has two alleles. The allele for black eyes, B, is dominant, while the allele for red eyes, b, is recessive. A mouse with full colour and black eyes was crossed with a himalayan mouse with black eyes. One of the offspring was albino with red eyes. Using the symbols above, draw a genetic diagram to show the genotypes and phenotypes of the offspring of this cross.
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
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9
For Examiner’s Use In the majority of photosynthetic organisms, fixation of carbon dioxide occurs in the Calvin cycle. is an outline of this cycle. 2 × glycerate phosphate (GP) ribulose bisphosphate (RuBP) 2 × triose phosphate (TP or GALP) CO2 State, the name of the five carbon sugar in the cycle the name of the enzyme that fixes carbon dioxide where in the chloroplast the Calvin cycle occurs the name of another compound that is produced in the light-dependent stage of photosynthesis that is used in the Calvin cycle. For Examiner’s Use shows the changes in the relative concentrations of RuBP and GP produced in the Calvin cycle before and after a light source is switched off. All other conditions are constant. concentrations and RuBP of GP time light dark light switched off RuBP GP Explain the changes in the relative concentrations of RuBP and GP after the light source is switched off.
13. Photosynthesis  →  13.1. Photosynthesis as an energy transfer process
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