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GCE JUN 2010 : (A2 2) Biochemistry, Genetics and Evolution - Revised

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Sp N ec e i w ca tio n Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2010 assessing Biochemistry, Genetics and Evolutionary Trends [AB221] AB221 Assessment Unit A2 2 *AB221* Biology TUESDAY 8 JUNE, MORNING TIME 2 hours. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Write your answers in the spaces provided in this question paper. Answer all nine questions. You are provided with Photographs 5.4A and B for use with Question 4 in this paper. Do not write your answers on this photograph. INFORMATION FOR CANDIDATES The total mark for this paper is 90. Section A carries 72 marks. Section B carries 18 marks. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. You are reminded of the need for good English and clear presentation in your answers. Use accurate scientific terminology in all answers. You should spend approximately 25 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B and awarded a maximum of 2 marks. Statistics sheets are provided for use with this paper. 6249.09 R For Examiner s use only Question Marks Number 1 2 3 4 5 6 7 8 9 Total Marks Examiner Only Marks Remark BLANK PAGE 6249.09 R 2 [Turn over Section A Examiner Only Marks 1 Remark (a) The diagram below represents the body plan of Hydra, a member of the phylum Cnidaria. A B C Name the layers A, B and C. A ________________________________ B ________________________________ C ________________________________ [2] (b) Describe three features found in members of the phylum Annelida, which are not found in Hydra. 1 ______________________________________________________ _______________________________________________________ 2 ______________________________________________________ _______________________________________________________ 3 ______________________________________________________ _____________________________________________________ [3] 6249.09 R 3 [Turn over 2 The diagram below summarises the various stages involved in the respiration of a glucose molecule. Examiner Only Marks Remark glucose glucose 6- phosphate A triose phosphate ADP + Pi ATP acetyl CoA B ADP H C H2O O2 CO2 CO2 (a) (i) Complete the diagram by naming the missing compound in the empty box. [1] (ii) State where in the cell process A occurs. _________________________________________________ [1] (iii) Name each of the processes which take place at locations B and C. B _________________________________ C _________________________________ [2] (b) The diagram summarises the respiration of glucose. Describe how fatty acids are respired. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [2] 6249.09 R 4 [Turn over 3 The Human Genome Project was organised to sequence all the nucleotides and map the genes present in human DNA. Examiner Only Marks Remark The graph below shows the number of mapped genes for different sized chromosomes. 2000 1800 Number of mapped genes 1600 1400 1200 X 1000 800 600 400 200 Y 0 0 50 100 150 200 Length of chromosome/M bases 250 300 (a) Describe the trend evident in the graph. _______________________________________________________ _____________________________________________________ [1] (b) The sex chromosomes, X and Y, are identified in the graph. Compare the number of genes in these chromosomes with other similar sized chromosomes. X _____________________________________________________ _____________________________________________________ Y _____________________________________________________ ___________________________________________________ [2] (c) Explain the significance for males of the difference between the number of the genes on the X and Y chromosomes. _______________________________________________________ _____________________________________________________ [1] 6249.09 R 5 [Turn over 4 Photograph 5.4A shows moss of the genus Polytrichum. Examiner Only Marks Remark (a) (i) Identify the stages in the moss life cycle indicated by X and Y. X __________________________ Y __________________________ [2] (ii) State the ploidy of the cells in stage X shown in photograph 5.4A. _________________________________________________ [1] Plants of the genus Polytrichum are upright and have well-developed rhizoids. They form dense tufts as shown in photograph 5.4A. These features allow Polytrichum species to grow on rocks and walls, both of which are relatively dry. (iii) Suggest how the following features allow these plants to grow in relatively dry areas. Well-developed rhizoids ________________________________________________ ________________________________________________ Growth in dense tufts ________________________________________________ ______________________________________________ [2] (iv) Explain how the plant is supported to keep it upright. ___________________________________________________ _________________________________________________ [1] 6249.09 R 6 [Turn over (b) Photograph 5.4B shows a moss plant of the genus Sphagnum. This moss covers the waterlogged soils of peat bogs. The lower part of the plant is dead and there are no rhizoids. Water and mineral ions are absorbed directly through the leaf-like structures. Examiner Only Marks Remark Suggest reasons for the following features, characteristic of Sphagnum. The absence of rhizoids and the dead lower part of the moss ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ The ability to absorb water and minerals ions into the leaf-like structures, an ability not shared by the leaves of ferns or flowering plants, members of the division Tracheophyta. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [4] 6249.09 R 7 [Turn over 5 The enzyme ribulose bisphosphate carboxylase (Rubisco) catalyses the reaction between ribulose bisphosphate (RuBP) and carbon dioxide. Examiner Only Marks Remark Genetically transformed plants can be produced using antisense RNA which results in the synthesis of less Rubisco enzyme. These are called reduced Rubisco plants . They grow slowly and are stunted. (a) (i) State the product of the reaction between ribulose bisphosphate and carbon dioxide. _________________________________________________ [1] (ii) In the Calvin cycle, ribulose bisphosphate is regenerated from triose phosphate. State what else is required for the regeneration of ribulose bisphosphate. ___________________________________________________ _________________________________________________ [1] (iii) Explain why the reduced Rubisco plants are slow growing and stunted. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (b) Leaves from a reduced Rubisco plant and an untreated (control) plant were used in a series of experiments. The graph opposite shows the rate of carbon dioxide assimilation by both plants at different light intensities. A temperature of 25 C and a high concentration of carbon dioxide were maintained at all light intensities. 6249.09 R 8 [Turn over Examiner Only Carbon dioxide assimilation rate/arbitrary units 50 Marks Remark 40 30 X X X X X X 20 X untreated (control) plant 10 X X reduced Rubisco plant 0 0 500 1000 Light intensity/arbitrary units 1500 (i) Explain the similar assimilation rates of both plants in low light intensities. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (ii) Explain the different assimilation rates of the plants in high light intensities. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] 6249.09 R 9 [Turn over (c) A second experiment was designed to measure the rate of carbon dioxide assimilation for both plants at varying carbon dioxide concentrations. Examiner Only Marks Remark In this experiment it would be necessary to maintain a temperature of 25 C and a high light intensity. (i) Explain why a relatively high temperature of 25 C should be maintained in the experiment. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (ii) Predict the result of this second experiment for both the reduced Rubisco plant and the untreated (control) plant. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (iii) Explain the result for the reduced Rubisco plant . ___________________________________________________ ___________________________________________________ _________________________________________________ [1] 6249.09 R 10 [Turn over BLANK PAGE (Questions continue overleaf) 6249.09 R 11 [Turn over 6 (a) In a survey of the relative sizes of island-dwelling mammalian species, each species was compared with mainland relatives. Four groups of mammals were surveyed. In each case the number of island-dwelling species smaller than or the same size as or larger than related species on the mainland were recorded. The results are shown in the table below. Examiner Only Marks Remark Number of island-dwelling species Smaller Same Larger than size than Lagomorphs (rabbits and hares) 4 4 1 Rodents (mice and rats) 6 3 60 Carnivores 13 1 1 Artiodactyls (even-toed mammals such as deer) 9 2 0 State two conclusions which might be drawn from the results. 1. _____________________________________________________ _______________________________________________________ 2. _____________________________________________________ _____________________________________________________ [2] (b) Field mice of the species Apodemus sylvaticus are common throughout Ireland. It was considered that the field mice of Rathlin Island are larger than the mainland field mice in Northern Ireland. The table below summaries data collected for the mass of a sample of adult field mice trapped on Rathlin Island and the mainland. Location of field mice Rathlin Number of mice in the sample (n) ( ) x 17 120 33.15 23.8 ( x) 2.56 1.65 Mean mass of mice Standard deviation of the mean Mainland A t-test can be used to compare the mean mass of the Rathlin and the mainland mice. 6249.09 R 12 [Turn over (i) State the null hypothesis for this test. Examiner Only Marks Remark ___________________________________________________ ___________________________________________________ _________________________________________________ [1] (ii) Calculate the value of t using the data in the table opposite. (Show your working.) Answer _______________ [2] (iii) State the degrees of freedom used in reading the statistical table. _________________________ [1] (iv) State the probability value for the calculated t. _________________________ [1] (v) State your decision about the null hypothesis. ___________________________________________________ _________________________________________________ [1] 6249.09 R 13 [Turn over (c) The mice population on Rathlin is isolated from mainland mice. In this island population large size may provide a selective advantage. Examiner Only Marks Remark (i) Explain the evolution of large size on Rathlin Island. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (ii) Explain what may eventually lead to a new mouse species on Rathlin. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] 6249.09 R 14 [Turn over BLANK PAGE (Questions continue overleaf) 6249.09 R 15 [Turn over 7 Labrador retrievers are dogs with black, brown or yellow coats. The coat colour is controlled by two independently-inherited genes which are not sex-linked. Examiner Only Marks Remark The alleles of a pigment gene at the B/b locus determine the amount of black pigment produced. The presence of a B allele results in a black coat. A brown coat is produced by the bb genotype. A second gene at the E/e locus influences the expression of the alleles at the B/b locus. The presence of the E allele allows the alleles at the B/b locus to be expressed. A yellow coat is always produced if the genotype is ee, no matter which alleles are present at the B/b locus. (a) (i) State the genotype of a pure breeding brown Labrador. _________________________________________________ [1] (ii) State the genetic term which describes the relationship between the B/b and E/e loci. _________________________________________________ [1] (b) Two black dogs known to be heterozygous for both genes (BbEe) were crossed. Determine the expected proportions of the offspring produced with respect to both genotypes and phenotypes. Show your working in a genetic diagram in the space below. [5] 6249.09 R 16 [Turn over (c) A litter of pups, which resulted from a cross between a yellow male Labrador and a black female, consisted of 7 yellow and 3 black pups. Examiner Only Marks Remark (i) With respect to the alleles at the E/e locus only, state the genotypes for the male and female parents. Give a reason for each of your answers. yellow male ______________ black female _____________ [2] (ii) Suggest an explanation for the lack of brown pups in the litter. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] 6249.09 R 17 [Turn over 8 Read the following passage concerning the gene coding for the muscle protein, dystrophin. Mutant alleles of this gene result in a lack of dystrophin, which leads to the progressive muscle-wasting disease, Duchenne muscular dystrophy (DMD). The gene for dystrophin is located on the X-chromosome. Sequencing techniques have shown that the gene contains 2.4 million nucleotide pairs. However, only 11,055 nucleotides codes for a dystrophin. The 79 coding regions (exons) within the gene are interrupted by non-coding regions (introns). Examiner Only Marks Remark 5 The disease DMD, is inherited as a sex-linked trait. DMD is rarely found in females, although they can be carriers of the mutant allele. Affected males show symptoms at five years old and most are wheelchair dependent at 12 years old. However, in a study of 77 cases of DMD, 43 had no family history of the 10 disease. Mutations in the female ovary can result in ova (eggs) having the allele causing DMD. This is not detected in DNA analysis of other tissues of the female, such as blood. An analysis of the DNA, using blood samples, from two families with DMD sons is shown below. The restriction enzyme BglII was used to cut the 15 DNA in the region of the dystrophin gene and cDNA probes were used to detect the different genetic markers (RFLPs). The diagrams below show the genetic markers (RFLPs) found in the parents and offspring in the two families. In family A the probe used identified markers i to vi. In family B 20 the probe used identified markers vii to xi. Family A Lane 1 2 3 4 5 Family B Family member Sister 1 (parent) DMD son of sister 1 DMD son of sister 1 Sister 2 (parent) Normal son of sister 2 Lane 1 2 3 4 5 Family member Father Mother DMD son DMD son Normal daughter Using this information, and your own understanding, answer the questions which follow. 6249.09 R 18 [Turn over (a) Calculate how many amino acids are in the protein, dystrophin [line 3]. (Show your working.) Examiner Only Marks Remark Answer __________________ [1] (b) Explain the term family history [line 10]. _______________________________________________________ _____________________________________________________ [1] (c) Mutations in the gene involve the deletion of a nucleotide [line 11]. Describe how the deletion of a nucleotide will change the gene and explain how the primary structure of the protein is altered. _______________________________________________________ _______________________________________________________ _______________________________________________________ _____________________________________________________ [2] (d) (i) In family A, compare the genetic markers identified by the genetic probe in the DMD sons and other members of the family. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] (ii) In family B, the genetic marker vii is present in both the DMD sons and their mother. Explain why their mother does not suffer from DMD. ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [2] 6249.09 R 19 [Turn over (iii) Comment on the inheritance of DMD in the two families. Examiner Only Marks Remark ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ _________________________________________________ [3] 6249.09 R 20 [Turn over BLANK PAGE (Questions continue overleaf) 6249.09 R 21 [Turn over Section B Examiner Only Marks Remark Quality of written communication is awarded a maximum of 2 marks in this section. [2] 9 (a) Write an account of the role of nucleic acids in the synthesis of proteins. [10] (b) Knowledge of the role of nucleic acids has been exploited to provide new sources of medically important proteins and new crops from genetically modified organisms. Discuss the safety precautions currently employed to overcome potential hazards of using genetically modified organisms and some of the ethical issues regarding the benefits and risks of gene technology. [6] _____________________________ (a) Write an account of the role of nucleic acids in the synthesis of proteins. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 6249.09 R 22 [Turn over Examiner Only _______________________________________________________ Marks Remark _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 6249.09 R 23 [Turn over _______________________________________________________ Examiner Only Marks Remark _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 6249.09 R 24 [Turn over (b) Discuss the safety precautions currently employed to overcome potential hazards of using genetically modified organisms and some of the ethical issues regarding the benefits and risks of gene technology. Examiner Only Marks Remark _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 6249.09 R 25 [Turn over Examiner Only _______________________________________________________ Marks Remark _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 6249.09 R 26 [Turn over THIS IS THE END OF THE QUESTION PAPER Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. 6249.09 R Sp N ec e i w ca tio n GCE Biology Advanced (A2) Assessment Unit A2 2 Biochemistry, Genetics and Evolutionary Trends Summer 2010 Photographs 5.4 A and B (for use with Question 4) A B X Y Dr Jeremy Burgess/Science Photo Library Sidney Moulds/Science Photo Library 6249.03 110162 [Turn over

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Additional Info : Gce Biology June 2010 Assessment Unit A2 2 : Biochemistry, Genetics and Evolutionary Trends
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