2015 HCI H2 Biology Prelims Paper 2 Questions

CANDIDAT CENTRE N BIOLOG Paper 2 C Additional INSTRUCT There are number a provided a SECTION This secti o Write your SECTION This sectio 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 HWA CHO JC2 Preli Higher 2 TE NAME NUMBER GY Core Paper Materials: TIONS TO C four ques nd index n at the top of A on contains answers on B on contains 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 This ONG INST minary Ex Writing Pa CANDIDAT tion bookl e number in t the cover p eight ques n the lines / two questio 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. s document TITUTION xaminatio per TES ets ( I to IV) the spaces page of Boo stions. Answ / in the spac ons. Answ 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 t consists of n ) t o t h i s pa provided at oklets II, III a wer all ques ces provide wer any one where app ovided. HEET OF W swered. ] at the en r is expecte u do not s h ts. d English a f 21 printed IN NU aper. Writ e t the top o f and IV. stions. ed. e question. ropriate. WRITING d of each ed, where how your and clear pages and C T DEX UMBER e your nam this cover 3 blank pa Fo Que 9 / To T GROUP 9 27 Au me, CT grou page and o ages. or Examine estion 1 2 3 4 5 6 7 8 / 10 otal 14S ___ 9648 / 02 ugust 2015 2 hours up, Centre on the lines ers' Use Marks / 9 / 10 / 10 / 9 / 12 / 9 / 10 / 11 / 20 / 100 e s 9 0 0 9 2 9 0 0 0

© Hwa QUESTION Fig. 1.1 sh of haemog (a) Desc Chong Institu N 1 hows a mole globin. cribe the rol ution 2015 SECT ecule of hae le of the hae B ION A: ST emoglobin. em group in 2 BOOKLET TRUCTUR The haem Fig. 1.1 n haemoglo 9648 H2 T I ED QUEST group plays obin. Biology / Pre TIONS s an importa eliminary Exa ant role in t am / Paper 2 the function [2] 2 n

3 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exam / Paper 2 (b) Discuss the advantages of having four subunits in haemoglobin. [3] The Greylag goose and the Andean goose have different haemoglobin structures. Possession of a haemoglobin with high oxygen affinity helps the A ndean goose to adapt to high altitudes. Greylag goose lives in the Indian plains, whereas t he Andean goose lives in the High Andes. The haemoglobin of the Andean goose differs from that of the Greylag goose by nine replacements in the -chain and seven in the -chain. (c) Explain how the differences in haemoglobin structure of the Greylag and Andean geese contribute to their different oxygen affinities. [4] [Total: 9]

© Hwa QUESTION Fig. 2.1 sh cycle. (a) Disti n (b) Des c Chong Institu N 2 hows how D nguish betw cribe the rol ution 2015 DNA polyme ween the he les of DNA erase intera elical structu polymerase 4 acts with a D Fig. 2.1 ures shown e in the S p 9648 H2 DNA molec in regions hase of the Biology / Pre ule during t X and Y. cell cycle. eliminary Exa the S phase am / Paper 2 e of the cell [2] [2] 2 l

5 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exam / Paper 2 Fig. 2.2 shows the structure of dideoxycytidine triphosphate (ddCTP), a potential replication substrate. Fig. 2.2 (c) ddCTP was added to a DNA replication reaction in large excess over the concentration of deoxycytidine triphosphates (dCTP). Explain how the addition of ddCTP would affect DNA replication. [4] (d) ddCTP is used in DNA sequencing reactions to determine the DNA base sequence. In such reactions, ddCTP is added at 10% the concentration of the dCTP. Suggest how ddCTP facilitates the determination of DNA base sequence. [2] [Total: 10]

6 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exam / Paper 2 [BLANK PAGE]

7 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exam / Paper 2 Candidate Name: CT Group: 14S______ BOOKLET II (SECTION A CONTINUED) [BLANK PAGE]

© Hwa QUESTION Human T- called T-c e infects CD Fig. 3.1 sh (a) With (i) (ii) (b) Sugg Chong Institu N 3 lymphotrop ell leukae m 4+ T cells. ows the str reference t suggest w HTLV-1, is describe t cells. gest how HT ution 2015 pic virus ty p mia. Like t h ructure of a to Fig. 3.1, why structu r s crucial in the roles of TLV-1 infec pe 1 (HTL V he human mature HT re C, the f i its classifica structures A ction could le 8 V-1) is a re immunodef LV-1 particl Fig. 3.1 irst viral e n ation as a re A and B in ead to the o 9648 H2 trovirus th a ficiency vir u le. nzyme invo etrovirus. the reprod onset of T-c Biology / Pre at brings a b us (HIV), H lved in the uctive cycle cell leukaem eliminary Exa bout a for m HTLV-1 pr e reproductiv e of HTLV-1 mia. am / Paper 2 m of cance r edominantly ve cycle o f [1] 1 in CD4+ T [2] [1] 2 r y f T

© Hwa HIV is an o AIDS occu Fig. 3.2 sh time period Fig. 3.3 s reproductiv Chong Institu other retrov urs ten years hows the inf ds. shows infe c ve cycle. ution 2015 virus that l e s on averag fection stag cted CD4 + ads to Acq ge after infe es of HIV in T cells w 9 quired Immu ection. n humans w Fig. 3.2 with immat u Fig. 3.3 9648 H2 unodeficien whereby X, ure HIV p a Biology / Pre cy Syndrom Y and Z re articles in eliminary Exa me (AIDS). epresent thr the late s am / Paper 2 Full blow n ee different tage of it s 2 n t s

10 © Hwa Chong Institution 2015 9648 H2 Biology / Preliminary Exam / Paper 2 (c) With reference to Fig. 3.2 and 3.3, (i) identify the time period(s) which correspond(s) to this late stage of HIV reproductive cycle shown in Fig. 3.3. [1] (ii) describe what happens during this stage of HIV reproductive cycle. [3] (iii) suggest how infection by HIV could cause diseases in time period Z. [2] [Total: 10]