2025 TMJC H2Bio PE P3 (A)

1 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology CANDIDATE NAME ( ) CIVICS GROUP H2 BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 22 September 2025 2 hours Candidates answer on the Question Paper. No additional materials are required. _________________________________________________________________________ This document consists of 27 printed pages and 3 blank pages. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION SUGGESTED ANSWERS

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology Section A Answer all questions. 1 Adult stem cells are undifferentiated cells that are found in most animal tissues. Adult stem cells can divide throughout their lifespan to form identical stem cells (self-renewal) or to form cells that can differentiate into the functioning cells of that tissue. (a) Uncontrolled cell division is a characteristic feature of tumour formation from a differentiated cell. (i) Describe two other features of tumour formation from a fully differentiated cell. [2] 1. Gain of function m utations of proto -oncogenes to oncogene and loss of function mutations of tumour suppressor genes. 2. Accumulation of these mutations in a single cell. 3. No contact-inhibition, where cells continue to divide even after contact with other cells. 4. Shorter/Faster G1 and G2 phase during cell cycle. 5. Activation of telomerase gene, to code for telomerase such that shortened telomeres are pelongated after each round of replication / shorten less quickly. 6. Normal cell cycle checkpoints are not functioning / proteins needed at the checkpoints not produced. 7. AVP Telomeres are non-coding DNA found at the end of the chromosomes. Adult stem cells have chromosomes with long telomeres. (ii) Explain why having long telomeres is an advantage to cells that are undergoing many rounds of cell cycles. [2] 1. After each round of DNA replication, telomeres shorten due to the end replication problem occurs. 2. Presence of telomeres ensure that no coding sequences/genes are eroded. 3. Long telomeres ensure telomeres do not reach / takes longer time to reach critical length and the cells do not undergo apoptosis.

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology (b) Haematopoietic stem cells (HSCs), also called blood stem cells, are adult stem cells that are located in the bone marrow. HSCs have a role in the formation of blood cells. Fig. 1.1 is an outline showing the formation of some of the different types of blood cell that can be formed from HSCs.