2024 SAJC Prelim Biology P3 (A)

1 SAJC / H2 Biology 9744/3 JC2 Prelim 2024 Civics Group Index Number Name (use BLOCK LETTERS) ST. ANDREW’S JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATIONS H2 BIOLOGY 9744/03 Paper 3 Wednesday 11th September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your name, civics group and index number 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 diagram, graph or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. Write your answers in the spaces provided on the question paper. All working for numerical answers must be shown. Conceptual error (C) Data Quoting (D) Expression (E) Misreading the question (Q) For Examiners’ Use 1 /30 2 /7 3 /13 4 or 5 /25 Total /75 This document consists of 12 printed pages. [Turn over] H2

2 SAJC / H2 Biology 9744/3 JC2 Prelim 2024 Answer all questions. Question 1 Colorectal cancer is the cancer of the colon and the rectum. Colorectal cancer is Singapore's top killer, affecting more than 1,865 cases each year. Colorectal ca ncer usually starts as a non-cancerous polyp (a growth of tissue) on the inner lining of the colon or rectum which may develop into cancer over time. The Wnt signaling pathway is associated with the widest array of biological processes, including cell proliferation, differentiation, and diseases such as neurodevelopmen tal diseases and cancer. Fig. 1.1 shows the Wnt signalling pathway. When Wnt signalling pathway is activated by binding of ligand Wnt to the LPR5/6-Frizzled receptor , β -catenin binds to other transcription factors and activate transcription of target genes. Fig. 1.1 (a) With reference to Fig. 1.1, state the level of gene expression that regulates β- catenin. ............................................................................................................................. [1] 1 Post translational DVL inhibits protein complex. Β-catenin is unphosphorylated and is activated. DVL is not activated. Β- catenin binds to protein complex. CK1α phosphorylates β-catenin and signals it for degradation by proteasome.

3 SAJC / H2 Biology 9744/3 JC2 Prelim 2024 (b) Suggest how does β-catenin bind to proteins APC and AXIN when the signalling pathway is inactivated. ............................................................................................................................. [2] 1 β-catenin is phosphorylated (by CK1α) 2 (ref, to recognise and bind via complementary conformation/ 3D shape) β- catenin has binding sites that recognizes the 3D conformation of APC and AXIN.; 3 (Ref. to R group interactions) PC and AXIN is held at the binding site via R group interactions such as hydrogen bonds and ionic bonds (c) In development of colorectal cancer, APC gene is one of the