2024 EJC Prelim Biology P3 (A)

©EJC 2024 9744/03/J2H2PRELIM/2024 [Turn over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examinations 2024 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME ANSWERS CIVICS GROUP 2 3 - REGISTRATION NUMBER H2 Biology Paper 3 Long Structured and Free-response Questions 9744/03 16 September 2024 2 hours Additional Materials: 12-page Answer Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on all the work you hand in. Write your answers in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use paper clips, highlighters, glue, or correction fluid/tape. Section A Answer all questions on the Question Paper. Section B Answer one question on the 12-page Answer Booklet provided. Write your answer to each part of the question on a fresh sheet of paper. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, ensure that you submit both the Question Paper and Answer Booklet. This document consists of 14 printed pages and 2 blank pages. For Examiner’s Use Section A 1 2 3 Section B 4 OR 5 Total 75

2 ©EJC 2024 9744/03/J2H2PRELIM/2024 Section A Answer all questions on the Question Paper. 1 The development of a mouse from a fertilised egg into an adult is regu lated by variations in DNA methylation. Fig. 1.1 shows the developmental stages of a mouse with corresponding levels of DNA methylation. R, S and T represent the zygote, blastocyst and embryo respectively. Fig. 1.1 (a) (i) Compare the features of a cell derived from the zygote with that from the inner cell mass of the blastocyst. [3] 3m = 2 similarities + 1 difference OR 1 similarity + 2 differences [Similarities] 1. Both cells are unspecialized and undifferentiated; (any one) 2. Both cells can be differentiated into specialized cells; 3. Both cells are capable of self-renewal and extensive proliferation; [Differences] 4. Cell derived from the zygote are totipotent while cell derived from inner cell mass of blastocyst is pluripotent; (A: former higher potency than latter); 5. Cell derived from the zygote has higher level of methylation while cell derived from inner cell mass of blastocyst has lower level of methylation; R: Cell derived from the zygote is a zygotic stem cell while cell derived from the inner cell mass of the blastocyst is an embryonic stem cell [Identity; not a feature difference] developmental stage zygote blastocyst embryo egg cell zygote morula blastocyst embryo adult relative level of DNA methylation R T S sperm cell

3 ©EJC 2024 9744/03/J2H2PRELIM/2024 [Turn over (ii) Explain how changes to DNA methylation from R to S bring about differentiation. [4] 1. Relative level of DNA m