2016 HCI H1 Biology Prelims P2 Questions

HWA CHONG INSTITUTION JC2 Preliminary Examination Higher 1 CANDIDATE NAME CT GROUP 15S ___ CENTRE NUMBER INDEX NUMBER BIOLOGY 8875 / 02 Paper 2 Core Paper 13 September 2016 Additional Materials: Writing Paper 2 hours INSTRUCTIONS TO CANDIDATES Write your name and CT group in the spaces provided at the top of this cover page. SECTION A This section contains four questions. Answer ALL questions. Write your answers on the lines / in the spaces provided. SECTION B This section contains two questions. Answer any one question. Your answers must be in continuous prose, where appropriate. Write your answers on the writing paper provided. BEGIN EACH PART ON A FRESH SHEET OF WRITING PAPER. A NIL RETURN is required for questions not answered. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or question part. The use of an appropriate scientific calculator is expected, where appropriate. You may lose marks if you do not show working or if you do not use appropriate units. You are reminded of the need for good English and clear presentation in your answers. This document consists of 12 printed pages. For Examiners' Use Question Marks 1 / 9 2 / 8 3 / 9 4 / 14 5 / 6 / 20 Total / 60

2 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 SECTION A: STRUCTURED QUESTIONS QUESTION 1 (a) Explain the role of helicase in DNA replication. [2] Cytarabine is a drug used to treat certain cancers. It prevents DNA replication. Fig. 1.1 shows the structures of cytarabine and the DNA base cytosine. Fig. 1.1 (b) Explain how cytarabine prevents DNA replication. [2] cytarabine cytosine

3 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 Fig. 1.2 shows information about the movement of chromatids in a cell that has just started metaphase of mitosis. Fig. 1.2 With reference to Fig. 1.2, (c) (i) state the duration of metaphase in the cell. [1] (ii) complete line Y on the graph. [1] distance between chromatids distance between each chromatid and the pole to which it is moving distance / µm key time after start of metaphase / minutes start of metaphase

4 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 (iii) account for your answer in (c)(ii). [3] [Total: 9]

5 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 QUESTION 2 The unicellular green alga, Chlorella, a photosynthetic eukaryote is mass produced and harvested by commercial suppliers for use as a health food supplement. Fig. 2.1 shows the effect of carbon dioxide concentration on the light-independent stage of photosynthesis in Chlorella. The following steps were carried out in a study:  a cell suspension of Chlorella was illuminated using a bench lamp.  the suspension was supplied with carbon dioxide at a concentration of 1% for 200 seconds.  the concentration of carbon dioxide was then reduced to 0.03% for a further 200 seconds.  the concentration of RuBP and glycerate-3-phosphate (GP) were measured at regular intervals.  the temperature of the suspension was maintained at 25 oC throughout the investigation. Fig. 2.1 (a) (i) State precisely where RuBP and GP are located in the chloroplast. [1] (ii) Explain why the concentration of RuBP changed between 200 and 275 seconds. [2] concentration / arbitrary units time / s

6 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 (b) Suggest how the decrease in the concentration of GP leads to a decrease in harvest for commercial suppliers of Chlorella. [2] (c) In the light dependent stage, illumination of chloroplasts is important for maintaining the high pH in the stroma. Explain how the illumination of chloroplasts maintains the high pH in the stroma. [3] [Total: 8]

7 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 QUESTION 3 About three million years ago, the ancestors of mammoths migrated from Africa into Europe and Asia. There, about 1.7 million years ago, the steppe mammoth evolved and became adapted to the cooler conditions. Fig. 3.1 shows a steppe mammoth. Fig.3.1 Then, about 700 000 years ago, as the climate changed and the Artic became much colder, the woolly mammoth evolved. The w oolly mammoth showed a number of obvious adaptations that help it to survive in the much colder Artic. (a) (i) Suggest and explain one such adaptation in the woolly mammoth. [2] (ii) Explain how natural selection may have brought about the evolution of the woolly mammoth from the steppe mammoth. [4]

8 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 A frozen, 43 000 year old woolly mammoth was found in Siberia. Its DNA was extracted and sequenced. The sequences of the genes coding for the α and β chains of haemoglobin were compared with those of modern Asian elephants. The results suggested that, when compared with Asian elephants:  there was only one different amino acid in the woolly mammoth’s α chains  there were three different amino acids in the woolly mammoth’s β chains. (b) Explain the likely effect of these differences on a molecule of mammoth haemoglobin. [3] [Total: 9]

9 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 QUESTION 4 An analysis of genes on separate loci in maize plants was carried out. In the experiment, pure- breeding maize plants with purple and smooth grains were crossed with pure-breeding maize plants with yellow and shrunken grains. All the plants in the F1 generation have purple and smooth grains. The F1 plants were then cross-pollinated. The following results were produced in the F2 generation: purple and smooth 204 purple and shrunken 72 yellow and smooth 69 yellow and shrunken 21 (a) Using the symbols A and a for colour of grain and B and b for texture of grain, draw a genetic diagram to explain these results. [4]

10 © Hwa Chong Institution 2016 8875 H1 Biology / Preliminary Exam / Paper 2 (b) Explain why yellow and shrunken grains breed true. [2] Lack of vitamin A in the diet is a major problem in the rice-based societies of south-east Asia. Rice plants produce the precursor of vitamin A, β-carotene, in their green tissues, but not in the edible endosperms of their seeds. Rice seeds lack the enzymes for two steps of the pathway for β-carotene production. The genes for these two enzymes have been inserted into rice embryos by genetic engineering, giving rise to Golden RiceTM. This rice produces seeds containing β-carotene. The added genes were:  the psy gene from daffodil plants,  the crt 1 gene from the bacterium Erwinia uredovora. (c) Explain why it is possible for rice plants to express genes from a bacterium. [1] The following steps were taken to produce Golden RiceTM:  step 1 – a length of DNA was made includi