2013 HCI H2 Biology Prelims Paper 1 Questions

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3 © Hwa Chong Institution 2013 9648 H2 Biology / JC2 Preliminary Examination / Paper 1 3 The table shows the results of food tests carried out to identify two types of biomolecules. test-tube reagent added to test-tube sodium hydroxide + copper sulphate Benedict's solution iodine in potassium iodide X purple brick red brown Y blue blue blue-black Z purple blue blue-black Which conclusion is consistent with the results? A Only albumen and sucrose had been placed in tube X. B Only maltose and starch had been placed in tube Z. C Only starch and sucrose had been placed in tube Y. D Only starch and sucrose had been placed in tube Z.

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6 © Hwa Chong Institution 2013 9648 H2 Biology / JC2 Preliminary Examination / Paper 1 6 Nocodazole is a chemical used in the study of mitosis. It causes all mitotic cells to be arrested at metaphase. Which statement(s) correctly identify how nocodazole might work? 1 Inhibits chromatin condensing in the nucleus 2 Prevents replication of the centrioles 3 Stops sister chromatids migrating to opposite poles A 3 only B 1 and 2 only C 1 and 3 only D All of the above 7 A double-stranded DNA molecule is 10 kb long. Which row correctly describes the structure of this DNA molecule? number of nucleotides number of complete turns length of DNA molecule / m A 10000 1000 3.4 B 20000 1000 0.34 C 20000 1000 3.4 D 20000 10000 3.4 8 An alien organism was found and investigated. Like eukaryotes, it has a linear double- stranded DNA genome. When DNA replication was examined, it revealed that although the process is semi-conservative, no Okazaki fragments were observed in all the multiple replication forks. In addition, the end-replication problem was not observed. Which statement correctly explains this phenomenon? A Alien DNA is antiparallel. B Alien DNA replication only starts at the 3’ end of each template strand. C Alien DNA polymerase synthesises DNA in both 5’ to 3’ and 3’ to 5’ directions. D Alien DNA ligase is not involved in the DNA replication process.

7 © Hwa Chong Institution 2013 9648 H2 Biology / JC2 Preliminary Examination / Paper 1 9 You have three different double-stranded DNA molecules, each of which you incubate (separately) in solution that is heated from 25 °C to 100 °C to denature the double-stranded molecules. Molecule 1 is 1000 bp long and has a G-C content of 70 %. Molecule 2 is 1000 bp long and has a G-C content of 50 %. Molecule 3 is 2000 bp long and has a G-C content of 40 %. Which statement is likely to be the correct prediction of the denaturation of these molecules? A Molecule 2 will denature at the highest temperature. B Molecule 3 will denature at the highest temperature. C Molecules 1 and 2 will denature at a higher temperature than Molecule 3. D All three molecules will denature at the same temperature. 10 Which statements correctly describe the structure and function of prokaryote ribosomes? 1 Prokaryote ribosomes are smaller than eukaryote ribosomes and sediment at 70S. 2 A prokaryote ribosome consists of two subunits, one of 50S and one of 30S. 3 In prokaryotes, ribosomes translate mRNA in the same cellular compartment in which it is transcribed. 4 In prokaryotes, ribosomes can begin translating mRNA before its synthesis has been completed. 5 A prokaryote ribosome can accommodate only one tRNA at a time. A 1, 3 and 5 only B 2, 4 and 5 only C 1, 2, 3 and 4 only D All of the above

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