2025 JPJC H2Bio PE P3 (QP)

9744 / 03 [Turn over NAME : CLASS : JURONG PIONEER JUNIOR COLLEGE JC2 Preliminary Examination 2025 BIOLOGY Higher 2 9744/03 15 September 2025 Paper 3 Long Structured and Free-response Questions 2 hours Additional Materials: Answer Booklet READ THESE INSTRUCTIONS FIRST Write your class and name in the spaces at the top of this page. 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 any one question on the separate Answer Booklet provided. 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. For Examiner’s Use 1 2 3 Section B Total This document consists of 17 printed pages and 3 blank pages.

2 JPJC/JC2 H2 Biology/PE/2025 Section A Answer all questions. 1 Following a body injury, bone marrow stem cells migrate to the site of damage, where they undergo cell differentiation to replace damaged cells. In eukaryotes, cell growth and division are tightly regulated processes to ensure proper repair. Cells will only pass specific checkpoints in the cell cycle if certain conditions are met, one of which is the presence of growth factors. Fig. 1.1 shows how this differentiation occurs. Fig. 1.1 (a) (i) Outline how SCFR is produced and transported to the cell surface. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [4] (ii) Suggest how SCFR is destroyed by a lysosome. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [1]

3 JPJC/JC2 H2 Biology/PE/2025 [Turn over Fig. 1.2 shows an example of how signals from growth factors are transduced to result in cell growth and division. The KRAS protein is a G -protein encoded by KRAS proto- oncogene. Fig. 1.2 (b) Describe the role of the KRAS protein in the transduction of signal fr om growth factors. ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ............................ [3]

4 JPJC/JC2 H2 Biology/PE/2025 (c) Mutations in KRAS proto-oncogene are common in colorectal (colon and rectum) cancer. The oncogene arises from the proto-oncogene by a mutation called G12D. Fig. 1. 3 shows part of the base sequence of the template strand of the KRAS proto-oncogene and the corresponding part of the oncogene. The corresponding parts of the primary structures of the two encoded KRAS proteins involved in GTPase activity are also shown. amino acid position 6 7 8 9 10 11 12 KRAS proto-oncogene 3’ … GAA CAC CAT CAA CCT CGA CCA … 5’ normal KRAS protein leu val val val gly ala gly KRAS oncogene 3’ … GAA CAC CAT CAA CCT CGA CTA … 5’ mutant KRAS protein leu val val val gly ala asp Fig. 1.3 (i) State one possible environmental causative factor that increases the risk of G12D mutation shown in Fig. 1.3. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [1] (ii) With reference to Fig. 1.3, explain how the G12D mutation leads to colorectal cancer. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [5]

5 JPJC/JC2 H2 Biology/PE/2025 [Turn over (d) In a genetic study for colorectal cancer, two populations were screened for the G12D mutation. Table 1.1 shows the results of the study. Table 1.1 group total number of individuals number of individuals with G12D mutation without colorectal cancer (control group) 500 2 with colorectal cancer 400 120 (i) Calculate the relative risk (RR) of G12D mutation in the cancer group compared to the control group using the formula provided. risk of G12D in cancer group risk of G12D in control gRR p= rou relative risk = ................................ .... [1] (ii) Discuss whether conducting screening tests to detect the G12D mutation is an effective way to screen for colorectal cancer. ................................ ................................ ................................ ........................ ................................ ..................