2026 RI H2 Biology Prelims P3 Questions

© RI 2026 Preliminary Examination 9477/03 [Turn over RAFFLES INSTITUTION 2026 Year 6 Preliminary Examination Higher 2 BIOLOGY 9477/03 Paper 3 Long Structured and Free-response Questions 18th Sept 2026 2 hours Candidates answer on the Question Paper. Additional Materials: Writing paper. READ THESE INSTRUCTIONS FIRST Write your index number, CT group & name in the spaces at the top of this page. Shade in your student ID. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer either question 4 or 5 on the writing papers. 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. At the end of the examination, hand in Section A and B separately. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 17 printed pages. CIVICS GROUP CANDIDATE NAME INDEX NUMBER 6 S 0 3 2 Raffles Institution Internal Examination For Examiner’s Use Section A 1 / 32 2 / 12 3 / 11 Section B 4 or 5 / 20 Total / 75 2 6

2 © RI 2026 Preliminary Examination 9477/03 For Examiner’s Use Section A Answer all the questions in this section 1 Cancer stem cells (CSCs) possess characteristics associated with normal stem cells, including the ability to give rise to different cell types found in a tumour. CSCs persist in tumours as a distinct population and have been found to be responsible for relapse and metastasis. In different environments, the type of cells that make up the tumours are different. Fig. 1.1 shows one model of how CSCs give rise to different cells. Fig. 1.1 (a) With reference to Fig. 1.1, and using your understanding of characteristics of stem cell, describe the similarities in characteristics between CSCs and a named multipotent stem cell. ………..……………………………………………………………………………………………... ………..……………………………………………………………………………………………... ………..……………………………………………………………………………………………... ………..……………………………………………………………………………………………... ………..……………………………………………………………………………………………... ………..…………………………………………………………………………………………...[3]

3 © RI 2026 Preliminary Examination 9477/03 [Turn over For Examiner’s Use As CSCs develop to form cells of different shapes, their cell surface membrane will have certain glycoproteins, known as biomarkers, embedded in them. Biomarkers are potential tools to classify different types of cancers as each type of cancer has its own unique set of biomarkers. Table 1.1 shows a list of biomarkers associated with some cancer types. Table 1.1 type of cancer biomarkers breast cancer CD24, CD44, CD29, CD133, CD200 pancreatic cancer CD24, CD44, ESA, CD133, CXCR4 bone cancer CD44, CD105, Stro-1 colorectal cancer CD44, EpCAM, CD166, CD133 (b) With reference to Table 1.1, (i) identify one biomarker that can be found in the four types of cancer that is likely to be coded for by an oncogene, and suggest the role of this biomarker. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[2] (ii) suggest why each cancer cell type found in their respective location in the human body has its own set of unique biomarkers. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[2] (c) A benign tumour can become metastatic after a while. Explain how these changes happen. ………………………………………………………………………………………………............ ………………………………………………………………………………………………............ ………………………………………………………………………………………………............ ………………………………………………………………………………………………........[2]

4 © RI 2026 Preliminary Examination 9477/03 For Examiner’s Use (d) The comet assay is used to detect DNA strand breaks in individual cancer cells. Single cells are mixed in an agarose gel on a glass slide. Chemicals are added to dissolve the cell surface membrane and nuclear envelope, leaving behind a tight ball of DNA. The DNA is then subjected to agarose gel electrophoresis as shown in Fig. 1.2. Fig. 1.2 The slide was then stained to visualise the DNA which appears in the form of a “comet”. Cells with greater DNA damage exhibit a longer "comet tail" during electrophoresis. Fig. 1.3 shows an example of how a comet assay may be studied for one cell. Fig. 1.3 (i) Explain how a named property allows the chemicals to dissolve the cell surface membrane and the nuclear envelope. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[2] - current + tail length head tail moment length 250 µm

5 © RI 2026 Preliminary Examination 9477/03 [Turn over For Examiner’s Use (ii) Explain why cells with more DNA damage exhibit a longer “comet tail”. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[3] (iii) Determine the tail moment length in Fig. 1.3. Show your working. …………………………….[1]

6 © RI 2026 Preliminary Examination 9477/03 For Examiner’s Use (e) Drug M targets colon cancer cells, and causes DNA breaks. Fig. 1.4 shows the photos of colon cancer cells taken in the first three hours after drug M was administered. A comet assay was carried out. first hour second hour third hour Fig. 1.4 (i) With reference to Fig. 1.4, explain whether drug M is effective. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[2] (ii) Suggest two limitations of the comet assay. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[2]

7 © RI 2026 Preliminary Examination 9477/03 [Turn over For Examiner’s Use (f) Chimeric antigen receptor (CAR) T cell therapy is a type of immunotherapy for some types of blood cancer. T lymphocytes are first extracted from the patient before a modified lentivirus vector is used to introduce a CAR gene into the DNA, turning the T lymphocytes into CAR T cells. CAR is a genetically modified receptor that combines parts of an antibody with parts of a T cell receptor. Fig. 1.5 shows how a CAR-T cell is being made. Fig. 1.5 After the CAR T cells are made, they are treated with chemicals in a petri dish before they are injected back into the patient. The CAR T cells are able to recognise the cancer cells using their chimeric antigen receptor and destroy them. Wi