2024 NJC H2 Bio P3 QP

©NJC 2024 9744/03/Preliminary Examination [Turn over H NATIONAL JUNIOR COLLEGE, SINGAPORE Senior High 2 Preliminary Examination Higher 2 CANDIDATE NAME BIOLOGY CLASS 2bi2_____ R E G I S T R A T I O N NUMBER Biology Paper 3 Long Structured and Free-response Questions Candidates answer on the Question Paper. Additional Materials: Answer Booklet 9744/03 13 September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your name, Biology class and registration number on all the work you hand in. Write in dark blue or black pen. You may use an HB 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 in the separate Answer Booklet. 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 Section A 1 /30 2 /10 3 /10 Section B 4 or 5 /25 Total /75

2 ©NJC 2024 9744/03/Preliminar y Examination This document consists of 15 printed pages and 1 blank page.

3 ©NJC 2024 9744/03/Preliminary Examination [Turn over Section A Answer all the questions in this section. 1 Collagen is a key structural protein found in various tissues t hroughout the body. Its measurements can vary significantly depending on the type a nd function of the collagen. Type I collagen is the most abundant form. Fig. 1.1 shows the structure of type 1 collagen fibrils. Fig. 1.1 (a) (i) Describe the molecular structure of collagen and explain how its structure relates to its function. [5]

4 ©NJC 2024 9744/03/Preliminar y Examination ( i i ) Use Fig. 1.1 to calculate the number of rows of collagen molecules found in the diameter of collagen fibril, D. Assume that: ● t h e d i a m e t e r o f a c o l l a g e n m o l e c u l e i s 1 . 5 n m ● t h e l e n g t h o f h y d r o g e n b o n d b e t w e e n t w o r o w s o f c o l l a g e n m o l e cules is 3.0Å (angstroms). Show your working clearly. Give your answer to the nearest whole number. number of rows of collagen molecules in one collagen fibril = [3]

5 ©NJC 2024 9744/03/Preliminary Examination [Turn over (b) Osteogenesis imperfecta (OI) is a heritable disorder of connective tissues caused by abnormal synthesis or dysfunctional type I collagen. Each type 1 collagen molecule contains two COL1A1 polypeptides and one COL1A2 polypeptide. A study was carried out to examine the mutations in COL1A1 and COL1A2 genes in patients with OI. PCR was carried out to amplify the genes in segments, and the resulting PCR product was used for DNA sequencing to identify the nucleotide sequence. Fig. 1.2 shows a segment of COL1A1 gene, with the 5’ end starting at position 1. Fig. 1.2 ( i ) Describe the principle and procedure of PCR. [4] ( i i ) Use Fig. 1.2 to propose the sequence of the pair of primers used in PCR. forward primer: 5’ 3’ reverse primer: 5’ 3’ [2]

6 ©NJC 2024 9744/03/Preliminar y Examination Fig. 1.3 shows the gene maps COL1A1 a n d COL1A2 g e n e s w i t h m u t a t i o n s a n n o t a t e d . T h e numbered box represents the numbered exon while each line between the boxes represents the intron between two exons. The types of mutations are represented by symbols “del”, “dup” and “>”. Fig. 1.3 ( i i i ) With reference to Fig. 1.3, explain the effect of the mutations in exons and introns on type I collagen protein. exons introns [5]

7 ©NJC 2024 9744/03/Preliminary Examination [Turn over Osteogenesis imperfecta (OI) can also arise from de novo m u t a t i o n s ( D N M ) , w h i c h r e f e r t o sequence alterations not found in parents. Fig. 1.4 shows the pedigree of a family affected with OI. Patient 716 was diagnosed with OI at the age of 3 days. Her parents, individuals 710 and 711, are healthy without history of chronic or clinically significant diseases and are free of mutations known to cause OI. Her younger brother, individual 715, is normal and does not carry any mutation known to cause OI. Fig. 1.4 ( i v ) Describe how genetic variation is produced in sperms under normal conditions. [3]

8 ©NJC 2024 9744/03/Preliminar y Examination Fig. 1.5 shows how DNMs may be affected by gender and age. Fig. 1.5 ( v ) With reference to Fig. 1.4 and Fig. 1.5, explain how the OI condition is present in individual 716 but absent in individual 715 and their parents. [3]

9 ©NJC 2024 9744/03/Preliminary Examination [Turn over (c) Type I collagen is the most abundant protein in the human body. It is degraded slowly and its replacement synthesis is low. However, during wound healing, the cells can increase the production of type I collagen by several hundred-fold. Describe how the expression of type 1 collagen may be upregulated during wound healing. [5] [Total: 30]

10 ©NJC 2024 9744/03/Preliminar y Examination 2 Sahiwal cattle and Holstein Friesian cattle are known for their high milk yield. Milk yield is affected by heat stress due to higher temperatures which results in protein misfolding within cells. Cattle have several hsp genes that code for heat shock proteins (HSP s). The expression of HSPs increases in response to heat stress to help in refolding of proteins to their normal conformations. Fig. 2.1 shows the relative expression of HSPs in the Sahiwal cattle and Holstein Friesian cattle during summer (S) and winter (W) seasons. Fig. 2.1 (a) With reference to Fig. 2.1, describe the differences in the relative expression of HSPs in Sahiwal cattle and Holstein Friesian cattle. [3]