2015 RI H2 Biology Prelims Paper 2 Answers

© RI 2015 Preliminary Examination 9648/02 [Turn over RAFFLES INSTITUTION 2015 Year 6 Preliminary Examination Higher 2 BIOLOGY 9648/02 Paper 2 Core paper 16th SEPTEMBER 2015 2 hours Additional materials: Answer Sheet READ THESE INSTRUCTIONS FIRST Write your index number, CT group & name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer either ONE question. At the end of the examination, hand in your essay SEPARATELY. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 24 printed pages. CIVICS GROUP CANDIDATE NAME INDEX NUMBER 5 S 0 3 1 For Examiner’s Use Section A 1 / 9 2 /10 3 /12 4 /10 5 /10 6 / 9 7 / 9 8 /11 Section B 9 or 10 /20 Total /100

2 © RI 2015 Preliminary Examination 9648/02 For Examiner’s Use Section A Answer all the questions in this section. 1 Meristematic root tissue from a barley seedling was prepared and its chromosomes are observed under a microscope. Fig. 1.1 shows a cell from the root tissue at the metaphase stage of mitosis. Fig. 1.1 Fig. 1.2 shows the changes in amount of DNA at different stages of the barley life cycle. Fig. 1.2 (a) Mark out with an arrow clearly on Fig 1.2 which part of the graph corresponds to the Raffles Institution Internal Examination

3 © RI 2015 Preliminary Examination 9648/02 [Turn over For Examiner’s Use stage shown in Fig. 1.1. [1] Accept all part of line except the corners (b) From stages A to D in Fig. 1.2, state all stages (i) that has/have the same number of chromosomes as shown in Fig. 1.1; [1] A and B; (ii) has/have a different number of chromosomes as shown in Fig. 1.1. [1] C and D; (c) Explain how stages in Y lead to variation. [4] 1. Crossing over * between non-sister chromatids * of homologous chromosomes/bivalents/homologous pair takes place during prophase I*; Or where equivalent portions of non-sister chromatids* of homologous chromosomes break and rejoin during prophase I* 2. gives rise to new combination of alleles* / mixing of alleles from both parental chromosomes which creates genetic variation in gametes; A: new linkage groups in place of new combination of alleles 3. Independent assortment* of homologous chromosomes/bivalents/homologous pair at metaphase plate during metaphase I * and their subsequent separation during anaphase I OR Homologous