Cambridge A Level Biology 9700 — 2015 May/June Paper 4 · Variant 3

This document consists of 21 printed pages and 3 lined pages. DC (FD) 110440 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Level * 7 8 2 2 9 1 2 9 8 9 * BIOLOGY 9700/43 Paper 4 A2 Structured Questions May/June 2015 2 hours Candidates answer on the Question Paper. Additional Materials: Answer Paper available on request. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions. Section B Answer one question. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 2 3 4 5 6 7 8 Section B 9 or 10 Total

2 9700/43/M/J/15 © UCLES 2015 Section A Answer all the questions. 1 (a) Fig. 1.1 shows a section through part of a dicotyledonous leaf of the tea plant Camellia sinensis. Fig. 1.1 On Fig. 1.1, use label lines and letters to label each of the following parts: X – xylem tissue P – palisade mesophyll tissue. [2] (b) The leaves of C. sinensis have a large surface area and are thin. Explain how each of these two features help the leaf to carry out photosynthesis. … … … … … [2] (c) The lower epidermis contains stomata. (i) State one structural difference between a guard cell and other lower epidermal cells. … [1]

3 9700/43/M/J/15 © UCLES 2015 [Turn over (ii) Abscisic acid has an important role in the closure of a stoma. It promotes the loss of potassium ions from guard cells. Outline how the loss of potassium ions from guard cells will lead to the closure of a stoma. … … … … … … … [3] [Total: 8]

4 9700/43/M/J/15 © UCLES 2015 2 When preparing infertile women for in-vitro fertilisation (IVF), it is necessary to stimulate the growth and maturation of several ovarian follicles. This is done by giving daily injections of the glycoprotein hormone, follicle stimulating hormone (FSH). Each molecule of FSH has quaternary structure and consists of two different polypeptide chains, α and β. (a) Explain what is meant by quaternary structure. … … [1] (b) Human FSH can be extracted from women’s urine (u-hFSH). A procedure involving the use of monoclonal antibodies is used to produce purified u-hFSH. Suggest how monoclonal antibodies can be used to obtain purified u-hFSH from urine. … … … … … … … … [3] (c) Recombinant human FSH (r-hFSH) can be produced by adding the genes coding for the α and β polypeptide chains of FSH to mammalian ovary cells. Suggest why mammalian cells are needed to produce r-hFSH, rather than bacterial cells. … … … … [1]

5 9700/43/M/J/15 © UCLES 2015 [Turn over (d) In IVF treatment, a second hormone, human chorionic gonadotrophin (hCG) is injected when mature ovarian follicles (Graafian follicles) have developed. Draw a labelled diagram to show the structure of a mature ovarian follicle. [3]

6 9700/43/M/J/15 © UCLES 2015 (e) The effectiveness of r-hFSH was compared with that of u-hFSH. Women starting IVF treatment were randomly divided into two groups and given either r-hFSH or u-hFSH. The differences between the two groups of women after FSH treatment are shown in Table 2.1. Table 2.1 women receiving r-hFSH women receiving u-hFSH number of women 119 102 mean number of mature follicles per woman 13 8 concentration of oestrogen in the blood / nmol dm−3 6.55 3.95 (i) With reference to Table 2.1, compare the effects of treatment with r-hFSH and u-hFSH and suggest explanations for the differences. … … … … … … … … … [4] (ii) The probability of the results for the mean number of mature follicles per woman occurring by chance is  0.002. Explain what is meant by this probability. … … … … … [2] [Total: 14]

7 9700/43/M/J/15 © UCLES 2015 [Turn over 3 The monkey flower, Mimulus guttatus, is cross-pollinated by bumblebees. It does not normally self-pollinate. Since the number of bumblebees in many parts of the world is falling, an experiment was carried out in Kansas to investigate the effects on these plants of the loss of pollinators. • 1600 Mimulus plants were grown in a field. • 1600 Mimulus plants were grown in a glasshouse which bumblebees could not enter. Seeds were repeatedly collected and sown for several generations at each site. At first, the plants in the glasshouse produced few seeds, but after five generations the plants were able to self-pollinate and the number of seeds produced was almost the same as that of the plants in the field. After five generations, the flowers of the plants in the glasshouse were significantly smaller than those of the plants in the field. (a) Explain why offspring produced by cross-pollination and self-pollination differ in their genetic variation. … … … … … … … … [3] (b) Suggest how smaller flowers could lead to an increase in self-pollination. … … [1]

8 9700/43/M/J/15 © UCLES 2015 (c) Explain how natural selection produced the smaller flower size of the plants grown for five generations in the glasshouse. … … … … … … … … … … … … [5] [Total: 9]

9 9700/43/M/J/15 © UCLES 2015 [Turn over 4 The Santa Cruz tarplant, Holocarpha macradenia, is a tall annual plant that grows only in the coastal grasslands in California. An annual plant is one that grows, flowers, produces seeds and dies in less than one year. The tarplant used to be widely spread in California, but there are now only nine natural populations. It is listed as an endangered species. (a) (i) Suggest two reasons why the tarplant has become endangered. … … … … … … [2] (ii) State three reasons why it is important to conserve species. 1. … … … 2. … … … 3. … … … [3]

10 9700/43/M/J/15 © UCLES 2015 (b) Tarplant seeds can survive in the soil for several years. Dormant seeds can be encouraged to germinate by scraping the soil, which exposes them to light. This stimulates the production of gibberellin in these seeds, which brings about germination. Explain how gibberellin brings about germination in seeds. … … … … … … … … … … [4] (c) The long-term survival of tarplant seeds in the soil provides a store of seeds that can help to ensure the future survival of the tarplant. Little is known about the survival of tarplant seeds in the soil, or what percentage of these seeds is able to germinate. Researchers therefore used computer models to predict how these factors could affect the likelihood that the tarplant might become extinct. In their models they used: • high or low survival values of tarplant seeds in the soil • different germination percentages of tarplant seeds. The predictions of the models are shown in Fig. 4.1.

11 9700/43/M/J/15 © UCLES 2015 [Turn over 0 0 1 2 3 4 5 6 7 8 9 10 20 40 60 percentage germination of tarplant seeds risk of extinction / arbitrary units 80 100 low survival value of seeds in soil high survival value of seeds in soil Fig. 4.1 (i) With reference to Fig. 4.1, describe the effect of each of the following on the risk of extinction of the tarplant: high compared to low survival of the tarplant seeds … … … different germination percentages of the tarplant seeds. … … … … … … [3]

12 9700/43/M/J/15 © UCLES 2015 (ii) With reference to Fig. 4.1, discuss whether scraping the soil should be recommended as part of the management strategy to attempt to conserve the tarplant. … … … … … … … … [3] [Total: 15]

13 9700/43/M/J/15 © UCLES 2015 [Turn over Question 5 starts on page 14

14 9700/43/M/J/15 © UCLES 2015 5 Mole rats, Spalax ehrenbergi, are mammals that live in groups in underground burrows. They are blind, and communicate with each other through sound and scent. Males make a purring call when they are attempting to persuade females to mate with them. In Israel, the mole rats found in different parts of the country all look identical. However, there are actually four different populations with different chromosome numbers, which live in different climatic regions. These are shown in Table 5.1. This table also shows information about the purring calls used by the males in each population. The calls of the males were analysed by measuring the number of sound pulses per second, and also the frequencies of the sounds that they made. Table 5.1 chromosome number of population 52 54 58 60 climatic region in which population lives cool and humid cool and dry warm and humid warm and dry purring call made by males mean number of pulses per second 21.0 25.3 23.9 23.2 mean major frequency / kHz 595 555 583 562 (a) Explain why the chromosome number of each of the four populations of mole rats is an even number. … … … … … [2]

15 9700/43/M/J/15 © UCLES 2015 [Turn over (b) Researchers investigated how female mole rats from each of the four populations responded to purring calls made by males from the same population, and by males from different populations. A female was placed midway between two loudspeakers, and recorded calls from two males were played to her simultaneously. The researchers noted which loudspeaker the female moved towards. This was repeated with many different females from each population. The results are shown in Table 5.2. Table 5.2 population chromosome number percentage of females preferring the purring call of males from their own population 52 79 54 77 58 77 60 44 With reference to Table 5.2, describe the extent to which female mole rats show a preference for the purring calls of males from their own population. … … … … … [2] (c) With reference to the data in both Table 5.1 and Table 5.2, discuss whether these four populations of mole rats should be classified as different species. … … … … … … … … … [4] [Total: 8]

16 9700/43/M/J/15 © UCLES 2015 6 The Indian cobra (Naja naja) is a species of venomous snake found in South Asia. Fig. 6.1 shows an Indian cobra. Fig. 6.1 (a) The Indian cobra’s venom contains a toxin which causes muscle paralysis in mammals bitten by the snake. The toxin acts at cholinergic synapses. Suggest ways by which the toxin in cobra venom may cause muscle paralysis. … … … … … … … [3]

17 9700/43/M/J/15 © UCLES 2015 [Turn over (b) Describe the role played by calcium ions in synaptic transmission. … … … … … … … … [3] (c) Synapses slow down the rate of transmission of nerve impulses but have an important role in the nervous system. Outline two of the roles of synapses in the nervous system. … … … … … … [2] [Total: 8]

18 9700/43/M/J/15 © UCLES 2015 7 (a) Outline the process of glycolysis in a mammalian cell. … … … … … … … … … … … … … [6] (b) Within a mammalian cell, ATP can be produced in a number of ways, including: • substrate level phosphorylation during the Krebs cycle • oxidative phosphorylation. Table 7.1 compares both processes. Complete Table 7.1. Use a tick () if the statement is correct or a cross () if the statement is incorrect. The first row has been done for you. Table 7.1 statement substrate level phosphorylation oxidative phosphorylation enzymes are involved   occurs in cytoplasm occurs in mitochondria channel proteins are involved [3]

19 9700/43/M/J/15 © UCLES 2015 [Turn over (c) An investigation into the RQ values of germinating maize seeds was carried out. • A sample of maize seeds was soaked in water for one hour. • The mean RQ value of some of the seeds was then calculated and the remaining seeds were then planted in soil. • After 12 hours, the mean RQ value of some of the planted seeds was calculated. • The remaining seeds were allowed to germinate and grow into seedlings. • After 21 days, the mean RQ value of some of the seedlings was calculated. Table 7.2 shows the results of the investigation. Table 7.2 stage of germination and growth mean RQ seeds soaked in water 5.6 seeds after 12 hours in the soil 0.8 seedlings after 21 days 1.0 Suggest an explanation for each of the RQ values shown in Table 7.2. seeds soaked in water … … … … seeds after 12 hours in the soil … … … … seedlings after 21 days … … … … [6] [Total: 15]

20 9700/43/M/J/15 © UCLES 2015 8 In mice, the intensity of pigmentation of the fur is controlled by multiple alleles of a single gene. 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 (a) Explain how multiple alleles arise. … … … … … … [2] (b) Eye colour in mice is controlled by two alleles of a single gene, B/b: • allele B codes for black eyes • allele b codes for red eyes. A mouse with full colour fur and black eyes was crossed with a mouse with himalayan fur and 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. [6] [Total: 8]

21 9700/43/M/J/15 © UCLES 2015 [Turn over Section B Answer one question. 9 (a) Describe how the gene coding for human insulin can be obtained and inserted into a plasmid vector. [8] (b) Explain how bacteria can be genetically modified and then identified using antibiotic resistance genes. [7] [Total: 15] 10 (a) Describe the advantages of using batch culture for penicillin production and continuous culture for mycoprotein production. [8] (b) Outline the hybridoma method for the production of a monoclonal antibody. [7] [Total: 15] … … … … … … … … … … … … … … … … …

22 9700/43/M/J/15 © UCLES 2015 … … … … … … … … … … … … … … … … … … … … … … … … … … … …

23 9700/43/M/J/15 © UCLES 2015 [Turn over … … … … … … … … … … … … … … … … … … … … … … … … … … … …

24 9700/43/M/J/15 © UCLES 2015 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. … … … … … … … … … … … … … … … … … … … … … … … …

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the May/June 2015 series 9700 BIOLOGY 9700/43 Paper 4 (A2 Structured Questions), maximum raw mark 100 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants accepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore AVP alternative valid point (examples given as guidance)

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 1 (a) [2] (b) large surface area (to get) more, light / carbon dioxide ; A gas exchange I oxygen thinness small(er) / short(er) / reduced, diffusion distance for gases OR fast(er) diffusion of gases ; A named gas, either CO2 or O2 1 mark only if both points made but not related to features in italics [2] (c) (i) have chloroplasts / varying thickness of (cell) walls / no plasmodesmata ; [1] (ii) water potential / Ψ, of (guard) cell(s), increases / becomes less negative ; water leaves cell(s) ; (by) osmosis / down a water potential gradient ; I diffuses (guard cell) becomes, flaccid / less turgid / AW ; [max 3] [Total: 8] 2 (a) has more than one polypeptide ; A FSH has 2 / α and β, polypeptides R has four has, prosthetic group / non-protein part / carbohydrate / sugar ; [max 1] (b) 1 produce / make, monoclonal antibodies specific to (u-h)FSH / anti(u-h)FSH monoclonal antibodies ; 2 ref. to column / framework, for, attachment / immobilisation ; R test strip 3 urine, added to / flows past / passed over, antibodies ; 4 (so) allowing, hormone / (h)FSH, to bind (to monoclonal antibodies) ; 5 treatment needed to release, hormone / (h)FSH (from monoclonal antibodies) ; I filtering [max 3] P / palisade mesophyll (tissue) ; X / xylem (tissue) ;

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 (c) 1 sugars need to be added / glycosylation ; A bacteria cannot modify protein 2 needs, Golgi body / rough endoplasmic reticulum ; A bacteria lack, Golgi / rough endoplasmic reticulum 3 ref. to problems in bacteria with, introns / wrong promoter / secretion / ora ; [max 1] (d) labels to correct recognisable structures (secondary) oocyte ; R ovum zona pellucida ; corona radiata / cumulus oophorus ; fluid-(filled space) / antrum ; granulosa / follicle / follicular, cells ; theca ; [max 3] (e) (i) comparison 1 more mature follicles with r-hFSH ; ora 2 oestrogen (concentration), higher with r-hFSH ; ora 3 comparative data quote ; e.g. 13 v 8 mature follicles OR 6.55 v 3.95 nmol dm–3 oestrogen concentration OR manipulated figures e.g. difference of 5 / 2.6 nmol dm–3 / 62.5% increase (r) follicles / 65.8% (r) oestrogen explanation 4 (because) r-hFSH, purer / more concentrated / ora OR (some) u-hFSH, damaged by extraction technique / degraded ; [max 4] (ii) 1 difference / difference described, is significant ; 2 not due to chance ; A due to something other than chance 3 smaller than, critical value / value for significance of, 0.05 / 5% ; [max 2] [Total: 14]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 3 (a) self-pollination ora for cross-pollination 1 gametes / alleles / genes / DNA, come(s) from one parent ; 2 gives, less genetic variation / more genetic uniformity ; 3 results in inbreeding ; 4 increases homozygosity / decreases heterozygosity ; [max 3] (b) anthers and stigma / stamens and carpels, closer together ; [1] (c) 1 range of flower size in original population ; 2 genetic variation (affecting flower size) in original population ; I mutation 3 change in environment / selection pressure, is absence of, bees / insect pollination (in greenhouse) ; 4 plants with small, flowers / petals, are, selected for / reproduce / at a selective advantage ; ora 5 alleles for small size passed to offspring ; ora I gene 6 frequency of, advantageous / smallness, allele increases ; ora 7 directional selection ; 8 temperature / irrigation / space / competition, different in field and glasshouse ; 9 small size explanation linked to factor in mp8 ; [max 5] [Total: 9] 4 (a) (i) 1 habitat loss / urbanisation / roads / agriculture ; R deforestation 2 human damage (to plants) ; e.g. trampling / camping / picking 3 climate change ; e.g. drought / storms 4 soil erosion ; 5 loss of pollinators ; 6 use of herbicides ; 7 competition with / eaten by, introduced species ; 8 pollution ; [max 2]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 (ii) 1 to maintain biodiversity ; 2 to maintain, food chains / food webs / stability of ecosystems ; 3 to maintain, genetic diversity / genetic variation / gene pool ; 4 resources (for humans) ; e.g. biofuel / food / medicines / wood 5 aesthetic reasons / (eco)tourism ; 6 to maintain, nutrient cycle / soil structure / climate stability ; 7 idea of ethical duty ; [max 3] (b) 1 gibberellin moves (from embryo) to aleurone layer ; 2 gene, switched on / transcribed / used to make mRNA ; 3 amylase produced ; I released / stimulated 4 (amylase), hydrolyses / digests, starch to maltose ; I breaks down / converts / glucose 5 for, respiration / ATP / energy ; 6 for, growth / development / cell division / mitosis, in embryo ; 7 AVP ; e.g. role of, DELLA / PIF [max 4] (c) (i) survival: 1 less risk of extinction (for high seed survival compared with low survival) ; germination percentage: for low survival: 2 as % germination increases, risk of extinction decreases ; for high survival: 3 as % germination increases risk of extinction decreases until, 30–36 % germination, then risk of extinction increases ; 4 use of paired figures ; e.g. quote % germination and risk of extinction for each of: high v low [mp1] 2 points on low survival line [mp2] 2 points on high survival line [mp3] allow ± one grid square for figures [max 3]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 (ii) yes 1 (scraping) increases germination ; 2 more germination lowers risk of extinction ; ora 3 if seeds don’t survive long / for low survival value seeds, scraping is good ; no 4 if seeds do survive long-term / for high survival value seeds, a store of seeds remains in soil ; 5 (avoid risk of) all germinating at once and perhaps all dying ; [max 3] [Total:15] 5 (a) 1 two (complete) sets of chromosomes / diploid / 2n ; 2 one of each chromosome, from each parent / maternal and paternal ; 3 to allow (homologous) pairs to form during, meiosis / prophase 1 / reduction division ; [max 2] (b) most / high % / more than 70%, of females in three populations prefer calls from their own population ; less than half / 44%, of females in, one population / population 60, prefer calls from their own population ; ora [2] (c) yes 1 different chromosome numbers ; 2 cannot interbreed to form fertile offspring / hybrids infertile ; 3 (because) not all chromosomes will be able to pair in meiosis ; 4 live in different, habitats / climatic regions OR geographical isolation ; 5 (so) unlikely to interbreed / reproductively isolated ; 6 most females prefer males from their own population ; ora 7 differences in mating, call / behaviour ; no 8 some females, willing to mate with / prefer, males from other populations ; 9 phenotypically / morphologically, similar ; [max 4] [Total: 8]

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 6 (a) toxin may 1 bind to receptors on postsynaptic (membrane) ; 2 (so) stops ACh binding / inhibits depolarisation / no action potentials / Na+ ion channels stay shut ; 3 (so) stimulates ACh receptors / causes (continuous) depolarisation / causes action potentials / opens Na+ ion channels ; 4 reduces / stops, release / recycling, of ACh (by presynaptic neurone) ; 5 inhibits acetyl cholinesterase / AW ; R denatures [max 3] (b) 1 enter, presynaptic neurone / AW ; 2 causes vesicles (containing ACh) ; 3 to, move to / fuse with, (presynaptic) membrane ; 4 (so) ACh released (into synaptic cleft) / exocytosis ; [max 3] (c) 1 ensure one-way transmission ; 2 filter out infrequent impulses / temporal summation ; I weak 3 allow, interconnection / integration, of, nerve (cell) pathways / many neurones ; OR spatial summation / convergence of impulses / divergence of impulses ; 4 ref. memory / learning ; 5 idea of inhibitory effect ; [max 2] [Total:8]

Page 9 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 7 (a) 1 glucose phosphorylated by ATP ; 2 (forms) hexose / fructose, bisphosphate ; 3 raises energy level of / activates, glucose / sugar OR lowers activation energy of reaction ; 4 breaks down to two TP ; 5 6C
2 × 3C ; 6 hydrogen (atoms) removed / dehydrogenated / oxidised ; 7 2 reduced NAD formed ; A NADH / NADH2 8 ref. to 4 ATP produced / net gain of 2 ATP ; 9 pyruvate produced ; 10 AVP ; e.g. ref. to substrate level phosphorylation / dehydrogenase / phosphofructokinase / hexokinase [max 6] (b) substrate level phosphorylation oxidative phosphorylation enzymes are involved   occurs in cytoplasm   ; occurs in mitochondria   ; channel proteins are involved   ; [3]

Page 10 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 (c) seeds soaked in water 1 little / no, oxygen (in water) ; 2 (mostly) anaerobic respiration ; seeds after 12 hours in the soil 3 (more) aerobic respiration / less anaerobic respiration ; 4 mixture of substrates ; e.g. 2 of carbohydrates, proteins and lipids seedlings after 21 days 5 aerobic respiration ; 6 substrate is, glucose / carbohydrate ; 7 ref. to presence of leaves / photosynthesis ; [max 6] [Total:15]

Page 11 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 8 (a) gene mutation ; a change in the, base(s) / nucleotide(s) ; e.g. base, substitution / deletion / addition [2] (b) parental genotypes CCaBb x ChCaBb ; gametes CB Cb CaB Cab x ChB Chb CaB Cab ; allow on Punnett square offspring genotypes ; ; deduct one mark for each error max 1 ecf for offspring genotypes if only 4 given offspring phenotypes ; phenotypes linked to genotypes ; ChB CaB Chb Cab CB CChBB full black CCaBB full black CChBb full black CCaBb full black Cb CChBb full black CCaBb full black CChbb full red CCabb full red CaB CaChBB Him black CaCaBB albino black CaChBb Him black CaCaBb albino black Cab CaChBb Him black CaCaBb albino black CaChbb Him red CaCabb albino red [6] [Total:8]

Page 12 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 9 (a) 1 obtain mRNA from β cells (of islets of Langerhans of pancreas) ; 2 reverse transcriptase ; 3 make (single-stranded) cDNA ; 4 DNA polymerase used to make cDNA double stranded ; 5 sticky ends created ; A description 6 (obtain) plasmids ; 7 cut with restriction, endonuclease / enzyme ; A named e.g. EcoR1 8 ref. complementary sticky ends ; 9 cDNA / insulin gene, mixed with plasmid ; 10 DNA ligase ; 11 seals nicks in sugar-phosphate backbone ; R anneals [max 8] (b) 1 (recombinant) plasmids mixed with bacteria ; 2 (some) bacteria, take up plasmids / transformed ; 3 heat shock / calcium chloride solution / Ca 2+ ions / electroporation ; to identify bacteria containing plasmids 4 grow on, agar / medium, containing antibiotic (A) ; A ampicillin 5 plasmid contains, antibiotic (A) / ampicillin, resistance gene(s) ; 6 bacteria with plasmid survive ; ora to identify recombinant bacteria 7 replica plate ; A description e.g. sponge / velvet pad / absorbent paper 8 (onto) agar / medium, containing second antibiotic (B) ; A tetracycline 9 (tetR / B / 2nd) resistance gene inactivated (by insertion of new, DNA / gene) / AW ; 10 (ID) colonies from, 1st / ampicillin, plate that do not grow on, 2nd / tetracycline, plate ; [max 7] [Total:15]

Page 13 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 43 © Cambridge International Examinations 2015 10 (a) batch / penicillin 1 nutrients, decrease / run out ; 2 so, secondary metabolite / penicillin, made ; 3 fermenters can be used (after cleaning) for different process ; 4 if problem occurs only one batch affected ; 5 needs little, monitoring / attention (once set up) ; continuous / mycoprotein 6 (fungus) kept in, exponential / log, phase (of growth) ; 7 (so) high, biomass / yield / production rate ; 8 little / no, downtime ; 9 small, vessels / space, required; 10 cost-effective ; [max 8] (b) 1 mouse is injected with an antigen ; 2 wait for immune response to occur ; 3 clonal selection ; A description e.g. antigen binds to, specific / virgin, B cell 4 clonal expansion ; A description e.g. mitosis / division / cloning of B cells 5 B-lymphocytes / plasma cells, are extracted ; 6 from the mouse’s spleen ; 7 fused with, cancer / myeloma / tumour, cells ; 8 hybridoma cells formed ; 9 hybridoma cells producing antibodies are identified ; 10 cultured on a large scale (to secrete monoclonal antibodies) ; [max 7] [Total:15]