2025 YIJC [H2] Prelim P3 (A)_with Examiner Report

YISHUN INNOVA JUNIOR COLLEGE JC2 PRELIMINARY EXAM Higher 2 NAME INDEX NO CG BIOLOGY Paper 3 Long Structured and Free-Response Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/03 15 Sep 2025 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the spaces provided on the Question Paper. Indicate the question you have attempted at the top of page 18. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 25 printed pages and 1 blank page. For Examiner’s Use Section A 1 32 2 10 3 8 Section B 4 or 5 25 Total 75 Section A ANSWERS

2 ©YIJC 9744/03/PE/2025 [Turn over Answer all questions in this section. 1 Glioblastoma multiforme (GBM) is the most common and most aggressive form of brain cancer, often resulting in low survival rates. It is characterised by uncontrolled growth, abnormal chromosomal structures, altered gene expression, and increased glycolysis. The exact genetic cause of GBM is unknown, prompting research into possible mechanisms such as chromosomal aberrations and gene mutations. One focus is the epidermal growth factor receptor (EGFR) gene on chromosome 7, which encodes a receptor tyrosine kinase specific to certain growth factors . Patients with GBM often show overexpression of the EGFR gene. Aberrations in chromosome 7 and a significant increase in metabolic activity have also been detected. Fig. 1.1 (a) (i) Describe how accurate chromosomal segregation during nuclear division prevents cancer. 1 Accurate chromosome segregation ensures daughter cells receive the correct number of chromosomes/ same amount of DNA. 2 Errors (e.g. aneuploidy) can lead to loss/gain of genes, disrupting cell cycle regulation and contributing to cancer. Or prevent loss /gain of genes which may disrupt mitotic regulation and accumulation of such errors may contribute to cancer. [2] Examiner feedback: Most students did not give precise answer which included unnecessary elaboration of mitosis, meiosis, separation of the homologous chromosomes, and sister chromatids

3 ©YIJC 9744/03/PE/2025 [Turn over (ii) With reference to Fig. 1.1, explain how chromosomal aberrations can le