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GCE JAN 2010 : (A2 2) Reproduction, Genetics and Taxonomic Diver

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2010 Biology Assessment Unit A2 2 Module 5: Reproduction, Genetics and Taxonomic Diversity A2B21 assessing [A2B21] MONDAY 25 JANUARY, AFTERNOON TIME 1 hour 30 minutes. 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 seven questions. INFORMATION FOR CANDIDATES The total mark for this paper is 75. Section A carries 60 marks. Section B carries 15 marks. You should spend approximately 20 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. For Examiner s use only Question Number 1 2 3 4 5 6 7 Total Marks 5320 Marks BLANK PAGE 5320 2 [Turn over Section A Examiner Only Marks 1 Remark Complete the table below to identify five differences between mitosis and meiosis. Mitosis Meiosis [5] 5320 3 [Turn over 2 The flow diagram below shows steps in the process of plant tissue culture (micropropagation). Examiner Only Marks Remark Small piece (explant) of tissue is removed from a plant (e.g. a bud) The explant is transferred to a culture vessel containing nutrients A mass of undifferentiated cells (callus tissue) develops Callus tissue is transferred to a new culture medium roots and shoots stimulated Developing plants are separated and grown under optimum conditions (a) Outline the general purpose of plant tissue culture (micropropagation). _________________________________________________________ _______________________________________________________ [1] (b) Sterile conditions are used throughout the process. Explain why sterile conditions are necessary. _________________________________________________________ _______________________________________________________ [1] (c) Describe how callus tissue may be stimulated to initiate root and shoot development. _________________________________________________________ _______________________________________________________ [1] 5320 4 [Turn over (d) State two advantages of producing plants by plant tissue culture (micropropagation) rather than by seeds. Examiner Only Marks Remark 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] (e) Plant tissue culture (micropropagation) is increasingly used in conjunction with genetic engineering to propagate transgenic plants. Outline two additional steps, further to the steps shown opposite, which would be required in the production of transgenic plants. 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] 5320 5 [Turn over 3 The diagram below represents a transverse section through an earthworm (Lumbricus), a member of the phylum Annelida. Examiner Only Marks Remark D A E B F (a) Identify the cavities A and B. A _______________________________________________________ B _____________________________________________________ [2] (b) Identify the tissue layers D, E and F. D _______________________________________________________ E _______________________________________________________ F _____________________________________________________ [2] (c) Annelids possess a blood system to distribute food and oxygen throughout the body. Into which of the above tissue layers are food and oxygen absorbed before passing into the blood system? 5320 Food _________________________________________________ Oxygen ____________________________________________ [2] 6 [Turn over (d) While annelids possess a blood system, platyhelminths do not. Explain this difference with respect to the body plan of each phylum. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (e) Both annelids and platyhelminths have a digestive system. State two differences in the digestive systems in annelids and platyhelminths. 1. ______________________________________________________ _________________________________________________________ 2. ______________________________________________________ _______________________________________________________ [2] 5320 7 [Turn over 4 Huntington s disease is an hereditary disorder of the central nervous system in humans. It is caused by a faulty allele of a gene on chromosome 4. This allele produces an abnormal protein which leads to damage of nerve cells in areas of the brain. The loss of nerve cells is not fatal, but complications caused by symptoms reduce life expectancy. These symptoms generally only develop between the ages of 40 to 50 years, and persons possessing the faulty allele are frequently unaware of this until that age. Examiner Only Marks Remark (a) The faulty allele (H) is dominant to its normal allele (h). The frequency of the H allele in the UK is 2.5 10 5. (i) Calculate the frequency of heterozygotes, assuming the population to be in Hardy Weinberg equilibrium. (Show your working in the space below.) [2] (ii) Using the value calculated above, calculate the number of heterozygotes in a population of 62 million (the approximate population of the UK). [1] (iii) The number of diagnosed cases of Huntington s disease in the UK is approximately 2000. Suggest explanations for the discrepancy between this figure and the value calculated above. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] 5320 8 [Turn over (b) A population can only be regarded as being in Hardy Weinberg equilibrium if a number of assumptions are met. Examiner Only Marks Remark One assumption is that there is no selection operating on the gene. Discuss whether or not this is likely to be the case with the Huntington s disease allele (H). _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (c) A couple, one of whom has a parent with Huntington s disease, are concerned about starting a family. Explain how genetic counsellors might advise the couple of the risk of them having a child who would develop the disease. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (d) Genetic testing for possession of the H allele is possible, either of cells from a foetus (pre-natal testing) or of cells from an adult (post-natal testing), While some people may emphasise the advantages of genetic testing, others will argue that such testing is not ethical. Discuss some of the issues involved. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] 5320 9 [Turn over 5 The budgerigar, Melopsittacus undulatus, is an Australian parakeet. Examiner Only Marks Remark (a) Complete the table below to show the classification of the budgerigar. Kingdom Phylum Aves Psittaciformes Order Psittacidae Family Polytrichaceae Melopsittacus Species [2] Wild budgerigars display a predominantly light-green colour while the mantle (back) feathers are edged in black. Selective breeding in captivity has led to numerous colour forms with different inheritance patterns. One gene, which is autosomal, has two alleles demonstrating codominance: dd is light-green, Dd is dark-green while DD is olive-green. Another gene, which is sex-linked, has a recessive form, opaline, which reduces the width of the black edging on the mantle feathers: the alleles are designated X+ (non-opaline) and Xo (opaline). In budgerigars, the female is XY and the male is XX. (b) Explain the terms codominance and sex-linkage , and explain how each phenomenon can be distinguished in genetic crosses. Codominance __________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Sex-linkage____________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] 5320 10 [Turn over (c) Determine the genotype of the following phenotypes. Examiner Only Marks Light-green, opaline male ________________________________ Remark Dark-green, non-opaline female _________________________ [2] (d) Two budgerigars of the following genotypes were crossed. DDXoY DdX+Xo Determine the expected proportions of the offspring produced in terms of colour and gender. Show your working in a genetic diagram in the space below. [6] 5320 11 [Turn over 6 The bracken fern (Pteridium aquilinum) grows in dense stands rarely containing other plants. It is thought that phytotoxins leached by rain from the fern leaves are largely responsible for the absence of other plants. (a) The effects of bracken on seed germination and seedling growth of three species of coniferous tree, Douglas fir (Pseudotsuga menziensii), Scots pine (Pinus sylvestris) and Sitka spruce (Picea sitchensis), were investigated. In field experiments, both seed germination and seedling growth were measured in plots irrigated with water-soluble extracts of bracken leaves, while control plots had no bracken extract added. seed germination in bracken extract seedling growth in bracken extract control control 100 12 Mass of seedlings/g % germination 80 60 40 20 0 Douglas fir Scots pine 10 8 6 4 2 0 Sitka spruce Douglas fir Scots pine What conclusions can be made about the effect of bracken on the seed germination and seedling growth in the three species of coniferous tree? Sitka spruce Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] 5320 12 [Turn over (b) Phytotoxins could be contained in any part of the bracken: the leaves, the stem and the roots. Design a laboratory experiment to test which of these parts, if any, exhibited the most inhibitory influence on seed germination using lettuce seeds as a test organism. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] A number of chemical compounds, including cyanide, have been implicated in the various toxic properties of bracken to animals. Nevertheless, there are insects that eat bracken. These include larvae of sawfly species which feed on bracken leaves. (c) Wood ants have been shown to impose high rates of predation on larvae venturing onto the leaves. However, when sawfly larvae are attacked they respond by secreting a fluid which repels the ants. Suggest an explanation for the ability of sawfly larvae to repel foraging ants. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] 5320 13 [Turn over Bracken, in common with other ferns, has both a sporophyte and a gametophyte generation. Examiner Only Marks Remark (d) Give four distinct differences between the fern sporophyte and gametophyte. 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _________________________________________________________ 3. _______________________________________________________ _________________________________________________________ 4. _______________________________________________________ _______________________________________________________ [4] 5320 14 [Turn over BLANK PAGE (Questions continue overleaf) 5320 15 [Turn over Section B Examiner Only Marks Remark In this section you are expected to answer in continuous prose, supported, where appropriate, by diagrams. You are reminded that up to two marks in this question are awarded for the quality of written communication. [2] 7 Give an account of how evolutionary change may take place in populations, and how this could lead to speciation. [13] _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ 5320 16 [Turn over Examiner Only _________________________________________________________ Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ 5320 17 [Turn over Examiner Only _________________________________________________________ Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ 5320 18 [Turn over Examiner Only _________________________________________________________ Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ THIS IS THE END OF THE QUESTION PAPER 5320 19 [Turn over 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. 1312-011-1

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Additional Info : Gce Biology January 2010 Assessment Unit A2 2 - Module 5: Reproduction, Genetics and Taxonomic Diversity
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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