HCI 2024 Prelim H2 Bio P3 Ans

HWA CHONG INSTITUTION / 2023-2024 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 1 HWA CHONG INSTITUTION (COLLEGE SECTION) 2024 JC2 9744 H2 BIOLOGY PRELIMINARY EXAMINATIONS PAPER 3 MARK SCHEME QUESTION 1 (a) Outline the advantages of having such multistep pathways. [2] 1. ref. to signal amplification 2. ref. to coordination / regulation 3. ref. to specificity of response (b)(i) Explain why IL6 cannot act directly on the DNA in the nucleus. [2] 1. IL-6 is hydrophilic 2. cannot pass through cell membrane (b(ii) Based on your knowledge on RTKs and with reference to Fig. 1.1, explain how IL6 leads to a cellular response. [5] 1. IL6-IL6R complex binds to gp130 2. gp130 dimerises 3. ref. to cross-phosphorylation 4. JAK phosphorylates STAT3 5. dimerised STAT3 activate expression of gene (b(iii) Suggest how regulation of STAT3 activation is an example of negative feedback. [3] 1. ref to. relevant stimulus 2. ref. to gp130 degraded 3. ref. to idea of negative feedback in this context (c)(i) With reference to Fig. 1.2 and Table 1.1, identify and explain which region(s) of gp130 are required for IL6 signalling pathway. [3] 1. ref. to R4, R5, R6 required 2. ref. to relevant supporting data from Fig. 1.2 3. ref. to relevant supporting data from Table 1.1 (c)(ii) Explain how the structure of the transmembrane domain of gp130 contributes to its function. [2] 1. ref. to hydrophobic nature 2. ref. to embedding of gp130 within membrane (d) With reference to Fig. 1.3, explain the significance of process Q in the formation of membrane-bound and soluble forms of IL6R. [3] 1. ref. to alternative splicing 2. ref. to relevant supporting data from Fig. 1.3 3. ref. to relevant supporting data from Fig. 1.3 (e) Suggest why early detection of PDAC is challenging. [1] ref. to any valid reason

HWA CHONG INSTITUTION / 2023-2024 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 2 (f)(i) Using the information in Fig. 1.1 and Table 1.2, identify which gene is the best target for effective treatments and explain your choice. [3] 1. gp130 gene 2. ref. to relevant supporting data from Fig. 1.1 3. ref. to relevant supporting data from Table 1.2 (f)(ii) Table 1.3 shows a few genes that are often found to be mutated in PDAC patients. With your knowledge and the relevant data provided, complete Table 1.3 to predict: ● the level of gene expression, using “” or “” ● if the gene is a proto-oncogene (POG) or tumour suppressor gene (TSG). Table 1.3 gene level of expression POG or TSG p53  TSG STAT3  POG SOCS3  TSG [2] (g)(i) Calculate the amount of DEN to be injected into a 14-day old mouse that weighs 10 g. You should show your working. [1] 250 µg (g)(ii) Discuss the effect of gp130 on tumour initiation a