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 lead to GBM. 1 EGFR gene is a proto-oncogene 2 Gene amplification/ Addition/ Hyperactivity of EGFR gene on chromosome 7 leads to increased expression, hence GBM. [R] Loss of gene, normal chromosome is shorter than abnormal Examiner feedback: Most students were unable to identify EGFR as an proto-oncogene [2]

4 ©YIJC 9744/03/PE/2025 [Turn over Capsaicin is a lipophilic compound. It is abundant in Capsicum species (pepper) fruit and it is the main bioactive constituent responsible for tissue irritation and burning sensation. Capsaicin has shown significant potential as an effective chemopreventive agent. Chemoprevention refers to the use of agents that inhibit or delay the development of tumour and before the onset of tumour cell invasion. There is increasing interest in using capsaicin as an alternative cancer therapy. Fig. 1.3 shows some of the many effects of capsaicin in chemoprevention. ↑ shows that the activity of the named molecule that is enhanced by capsaicin. ↓ shows that the activity of the named molecule that is decreased by capsaicin. Fig. 1.2

5 ©YIJC 9744/03/PE/2025 [Turn over (b) (i) Tumours are known to secrete VEGF and MMP-9. With reference to Fig. 1.3, explain why capsaicin is an effective chemopreventive agent. 1 Capsaicin lowers the activity of VEGF and MMP-9, thereby inhibiting tumour growth/ angiogenesis and metastasis 2 Tumours secrete VEGF to stimulate the blood vessels formation that supply nutrients for tumour growth (idea of angiogenesis) OR AW prevent formation of blood vessels and supply of nutrients to tumours; 3 They also secrete MMP-9 to allow cancer cells to invade and spread (idea of metastasis) OR AW prevent the cancer cells from invading and spreading to establish secondary tumours ; [3] Examiner feedback: This part was generally well answered. Most candidates demonstrated a good understanding of the experimental context and were able to relate the role of capsaicin to the regulation of VEGF and MMP9 in cancer progression. Many candidates correctly identified that capsaicin reduced the expression of VEGF and MMP9, and were able to explain how reduced VEGF leads to decreased angiogenesis while reduced MMP9 results in lower rates of metastasis. In addition, most were able to define angiogenesis as the formation of new blood vessels and metastasis as the spread of cancer cells to secondary sites. A small number of candidates, however, misinterpreted the context by describing the effects of other molecules shown in Figure 1.2 rather than focusing on VEGF and MMP9 as required. This suggests the need to read the question carefully and ensure that responses remain focused on the molecules specified. Another group of candidates only stated that capsaicin reduced VEGF and MMP9 levels, without extending their answers to explain the consequences of this reduction, such as reduced blood vessel formation and reduced spread of cancerous cells to ot her tissues. When tackling data -based questions involving experimental figures, candidates should pay close attention to the molecules specified in the question and avoid diverting into unrelated aspects of the figure. It is also important to remember that examiners look for both identification of what is observed in the data and explanation of why this observation is biologically significant. For full credit, molecular changes must be linked clearly to their biological consequences in the context of the disease or process studied. Candidates are encouraged to use precise biological terms such as “angiogenesis” and “metastasis”, but these should be accompanied by clear explanations of what they mean in context.

6 ©YIJC 9744/03/PE/2025 [Turn over (ii) Cyclins interact with one of the classes of molecules that capsaicin affects. Identify this class of molecules in Fig. 1. 2 that cyclins interact with and explain how capsaicin’s effect on it could help to treat or prevent cancer. 1 Cyclin-dependent kinases (CDKs)/ Cell Cycle Molecules/ CDK 2 Capsaicin reduces the activity of CDKs and cause cell cycle arrest at the checkpoints ; 3 This slows or stops cell cycle progression, which can prevent uncontrolled cell division and reduce growth of cancerous cells; [3] Examiner’s feedback: This part of the question revealed greater variation in performance compared to the previous one. About half of the cohort were unable to correctly identify the class of molecules that cyclins interact with in the cell cycle from Figure 1.2. The intended answer was cyclin-dependent kinases (CDKs), and students were expected to provide the full name. Those who answered correctly often relied on the header provided in the figure, writing “cell cycle molecules” instead. While this was not the original answer in the mark scheme, credit was awarded for this phrasin