2015 HCI H2 Biology Prelims Paper 3 Questions

CANDIDAT CENTRE N BIOLOG Paper 3 A Additional INSTRUCT There are number a and CT gro STRUCTU Answer all Write your PLANNING Answer the Write your FREE RES Answer the Your answ Write your BEGIN E A PAPER. A NIL RET INFORMA The numbe question o The use of appropriate working or You are r presentatio This HWA CHO JC2 Preli Higher 2 TE NAME NUMBER GY Applications Materials: TIONS TO C four ques nd index n oup on the URED QUES l three ques answers on G QUESTIO e question i answers on SPONSE Q e question. wers must be answers on ACH PAR T TURN is req ATION FOR er of marks r part quest f an approv e. You m r if you do n reminded o on in your a s document ONG INST minary Ex s Paper and Writing Pa CANDIDAT tion bookl e number in t lines provid STIONS stions. n the lines / ON n booklet IV n the lines / QUESTION e in continu n the writing T ON A F quired for pa CANDIDAT s is given in tion. ved scientifi may lose m ot use appr of the nee d answers. t consists of TITUTION xaminatio d Planning Q per TES ets ( I to IV ) the spaces ded at the to / in the spac V. / in the spac uous prose, g paper pro FRESH S H arts not ans TES brackets [ c calculato marks if yo u ropriate unit d for goo d f 17 printed ns Question ) t o t h i s pa provided at op of the co ces provide ces provide where app ovided. HEET OF W swered. ] at the en r is expecte u do not s ts. d English a pages and IN NU aper. Writ e t the top o f over page o ed. ed. ropriate. WRITING d of each ed, where how your and clear 5 blank pa C T DEX UMBER e your nam this cover of Booklets I Fo Que T ages./g3 T GROUP 9 14 Septem me, CT grou page, and II, III and IV or Examine estion 1 2 3 4 5 Total 14S ___ 9648 / 03 mber 2015 2 hours up, Centr e your name V. ers' Use Marks / 12 / 15 / 13 / 12 / 20 / 72 e e 2 5 3 2 0 2

2 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3 BOOKLET I STRUCTURED QUESTIONS QUESTION 1 Restriction enzymes are used in recombinant DNA technology (RDT). Fig. 1.1 shows the palindromic recognition sequence of EcoRI, a restriction enzyme. 5’  N  N  G  A  A  T  T  C  N  N  3’ 3’  N  N  C  T  T  A  A  G  N  N  5’ Fig. 1.1 (a) Explain what is meant by the term palindromic. [2] The bacterial plasmid, pUC, is a useful cloning vector in RDT. A researcher is investigating the use of two restriction enzymes, EcoRI and BamHI, to clone gene X into pUC. Fig. 1.2 shows the results when pUC and recombinant pUC are treated with either EcoRI, BamHI or both. pUC / kb recombinant pUC / kb EcoRI BamHI both EcoRI BamHI both 7.0 4.0 4.0 7.0 4.0 4.0 3.0 2.0 1.0 2.8 2.0 1.0 1.2 1.0 0.8 0.2 Fig. 1.2

3 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3 (b) (i) Complete Table 1.1 to show the number of restriction sites in pUC and recombinant pUC. [1] Table 1.1 in pUC in recombinant pUC number of EcoRI sites number of BamHI sites (ii) Indicate the positions of EcoRI and BamHI restriction sites on the recombinant pUC by drawing in Fig. 1.3. Show the size of each fragment in kb. [2] Fig. 1.3 (iii) Identify which restriction enzyme, EcoRI or BamHI, is suitable for use to clone gene X. Give a reason for your answer. [2] recombinant pUC (8 kb) BamHI

4 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3 Human insulin can be synthesised in Escherichia coli using RDT. Fig. 1.4 outlines how a gene coding for human insulin is produced. mature mRNA for human insulin gene isolated step 1 single-stranded complementary DNA (cDNA) produced step 2 single-stranded DNA made into double-stranded DNA step 3 double-stranded DNA with additional noncoding sequences at both ends Fig. 1.4 (c) (i) Explain the significance of the use of mature mRNA in step 1. [3] (ii) Suggest why additional noncoding sequences are added in step 3. [1] (iii) Suggest an advantage of treating diabetics with human insulin produced by RDT. [1] [Total: 12]

5 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3 Candidate Name: CT Group: 14S______ BOOKLET II STRUCTURED QUESTIONS (CONTINUED) [BLANK PAGE]

© Hwa 3 QUESTION Leber’s co mutations photorecep Between 2 adeno-ass the insertio was injecte * recombina (a) Outli Chong Instit N 2 ngenital am in the RPE ptor cell dys 2007 and 20 sociated viru on of the n ed into the s ant AAV geno ne a mutati ution 2015 maurosis (LC E65 gene. sfunction an 010, a clinic us (AAV) wa ormal RPE subretinal s ome, AAV an ion that resu CA) is a gro Such mutat nd impaired cal trial to e as conducte E65 allele i n space of the nd eye are n ults in RPE6 6 oup of inher tions result d vision from evaluate the ed on 12 hu nto an AA V e retina. not drawn to s Fig. 2.1 65 deficienc 9648 H2 rited visual d t in RPE65 m birth. e efficacy of uman partic V vector, af t scale. cy. Biology / Pre disorders ca protein def f gene thera cipants with ter which t h reliminary Ex aused by va ficiency, wh apy using re h LCA. Fig. he recombi xams / Paper arious point hich causes ecombinant . 2.1 shows nant vector [2] r t s t s r

7 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3

8 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3 (b) Explain why the normal RPE65 allele was obtained from a genomic DNA library instead of a cDNA library. [2] (c) AAV is a non-enveloped virus. Suggest how the normal RPE65 allele enters the photoreceptor cell. [2] (d) Suggest why it is not necessary to include selectable markers in this study. [1] For each participant in the clinical trial, an eye was selected as the study eye for treatment with the recombinant AAV vector. The other eye was left untreated. Retinal sensitivity was assessed in 76 loci (locations) on the retina of each eye. (e) Suggest why one eye was left untreated. [2]

9 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exams / Paper 3

© Hwa 3 The invest retinal sen  pa r  pa r key study eye: (f) Des c Chong Instit tigators exa sitivity of tw rticipant 1 w rticipant 2 w cribe and ex ution 2015 amined the wo participa was adminis was adminis (solid line xplain how t effect of th nts whereby stered a low stered a high e) the results d 10 he dosage o y: wer dose, an her dose of Fig. 2.2 differ betwe 9648 H2 of normal R nd f the recomb untreated e een the two Biology / Pre RPE65 allele binant AAV eye: participants eliminary Ex e. Fig. 2.2 V vector. (dash s. xams / Paper shows the hed line) [3] r e