Ib Exam Paper 2011

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  • Topic: Rice, Allele, Oryza sativa
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N10/4/BIOLO/HP2/ENG/TZ0/XX

88106002

Biology
HigHER lEvEl
PaPER 2
Candidate session number

Tuesday 2 November 2010 (afternoon)
0

2 hours 15 minutes

0

INSTRUCTIONS TO CANDIDATES
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so. Section A: answer all of Section A in the spaces provided.
Section B: answer two questions from Section B. Write your answers on answer sheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided. • At the end of the examination, indicate the numbers of the questions answered in the candidate box on your cover sheet and indicate the number of sheets used in the appropriate box on your cover sheet.






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© International Baccalaureate Organization 2010

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SecTion a
Answer all the questions in the spaces provided.
1.

Gibberellin promotes both seed germination and plant growth. Researchers hypothesize that the gene GID1 in rice (Oryza sativa) codes for the production of a cell receptor for gibberellin. The mutant variety gid1-1 for that gene leads to rice plants with a severe dwarf phenotype and infertile flowers when homozygous recessive. It is suspected that homozygous recessive gid1-1 plants fail to degrade the protein SLR1 which, when present, inhibits the action of gibberellin. The graphs show the action of gibberellin on the leaves and α-amylase activity of wild-type rice plants (WT) and their gid1-1 mutants.

12
10

50

8
Length
of second
leaf / cm

60

40

6

α-amylase
activity / 30
units seed–1

WT

20

4
2
0

WT

10

gid1-1
0 10–9 10–8 10–7 10–6 10–5 10–4
Gibberellin concentration / mol dm–3

0

gid1-1

0 10–1110–1010–910–810–7 10–6 10–5
Gibberellin concentration / mol dm–3

[Source: adapted from M. Ueguchi-Tanaka et al. (2005) ‘Gibberellin-insensitive dwarf1 encodes a soluble receptor for gibberellin’. Nature, 437, pp. 693—698. Adapted by permission from Macmillan Publishers Ltd (c) 2005.]

(a)

(i)

[1]

State which variety of rice fails to respond to gibberellin treatment. ..................................................................

(ii)

The activity of α-amylase was tested at successive concentrations of gibberellin. Determine the increment in gibberellin concentration that produces the greatest change in α-amylase activity in wild-type rice plants (WT).

[1]

.................................................................. .................................................................. .................................................................. [1]

(iii) Outline the role of α-amylase during the germination of seeds. .................................................................. ..................................................................

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(Question 1 continued)
(b)

Discuss the consequence of crossing gid1-1 heterozygous rice plants amongst themselves for food production.

[3]

....................................................................... ....................................................................... ....................................................................... ....................................................................... ....................................................................... ....................................................................... ....................................................................... .......................................................................

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