2016 VJC H2 Biology Prelims Paper 2 Questions

1         VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2017 NAME : ____________________________________ CT CLASS : ____________________________________ H2 BIOLOGY 9744/2 Paper 2 Structured Questions 2 hours READ THESE INSTRUCTIONS FIRST Write your Name and CT Class on the cover page of this paper. Write in dark blue or blue pen. You may use a soft pencil for any diagrams or graphs. Do not use any staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided on the question paper. The use of an approved scientific ca lculator is expected, where appropriate. You may lose marks if you do not s how your working or if you do not use the appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 19 printed pages, including cover page For Examiner’s Use 1 2 3 4 5 6 7 8 9 Total

2         1 Fig.1 shows an electron micrograph of an organelle. There are two distinct groups of vesicles (Boxes B and C) associated with this organelle. Fig. 1 Source:https://ib-biology2010-12.wikispaces.com/Cell+Images (a) (i) Identify Organelle A. Support your answer with one observable feature, other than vesicles, shown in Fig 1. Organelle A: [2]

3         (ii) Describe the differences in the role of the vesicles in Boxes B and C.             [4] In Angelman syndrome, a severe and rare neurodevelopmental disorder, it has been reported that the lack of ubi quitin protein ligase E3A ( UBE3A) expression leads to a disruption of structure and function of Organelle A. (b) Suggest how the lack of UBE3A expression can lead to a disruption in the structure and function of Organelle A. [3] (c) State two characteristics, one in structure and one in chemical property that you would expect to see in ubiquitin protein ligase. [2] [Total:11]

4         2 An experiment to determine the effect of Compound K, a metabo lite derived from ginseng, on the expression of a gene (RUNX3) was carried out using a culture of human colorectal cancer cells. RUNX3 gene codes for a transcription factor. Cells were treated with Compound K for 72 hour s. Samples of cells were removed at specific time intervals. These cells were then lysed and the mRNA and proteins analysed. Fig 2 shows the changes in the HDAC (Histone Deacetylase) mRNA and HDAC protein over the 72 hour period. The thickness of the band is an indication of the concentration of the mRNA and proteins. Fig 2 (a) Explain the similarity in the pattern seen in both HDAC mRNA and HDAC protein. [2] (b) (i) What information about the gene expression of RUNX3 in the colorectal cancer cells can one conclude from the data at the beginni ng of the experiment? Explain your answer. [3] (ii) Suggest one way how your answer in (i) can affect the cell.

5         [3] (c) With reference to the data shown in Fig 2, suggest how Chemical K can bring about the change in the HDAC mRNA and protein. [2] (d) Suggest why HDAC mRNA instead of th e HDAC gene was analysed in this experiment. [2] [Total:12]

6         3 Diauxic growth is a two-phase growth response observed in a culture of bacteria of E. coli. This phenomenon (Fig. 3) was discov ered by Jacob and Monod who were awarded the Nobel prize for their ground br eaking study of how gene expression is regulated in prokaryotic organisms. They studied how glucose and lactose impact the growth of E. coli. Substrates X and Y are the two di fferent sugars that are introduced to the bacteria culture medium at the same time, to serve as carbon sources. Fig. 3 *Note: Optical density, measured in a spectrophotometer, is used as a measure of the concentration of bacteria in a suspension. (a) (i) Identify substrates X and Y. X: Y: [2]

7         (ii) Using your knowledge of gene expression in bacteria, explain how Fig. 3 supported their conclusion that the Lac operon is under dual control.             [4] (b) On Fig. 3, draw separate graphs to show the change in the concentration of the two substrates over time. Label your graphs clearly. [2] (c) Eukaryotes are structurally different from prokaryotes and hence exhibit differences in their control of gene expression. Explain two such differences. 1.       2.   [4] [Total:12]

8         4 Wild-types freshwater snails, Physa heterostropha have pigmented shells. When two pure-breeding albino snails were crossed and their F1 selfed, the F2 generation consists of 48 pigmented snails and 35 albino snails. (a) What do you understand by the term pure-breeding? [1] (b) Using appropriate symbols, draw a genetic diagram to explain the results obtained. Symbols: [1]                              [6] [Total:8]

9         5 Cells X and Y are two types of cells taken from a healthy individual and cultured in media that is similar to the actual conditions in the body. Fig. 5 illustrates the change in the telomere lengths of these cells with increasing rounds of cell division. M1 represent s the Hayflick limit where cells will leave the cell cycle (replicative senescence) while M2, termed cr isis, is characterised by widespread cell death, although some cells that survive M2 will be able to continue dividing. Fig. 5 (a) (i) Account for the decrease in the telomere length of Cell Y.         [4]

10         (ii) Explain why there is a limit to the number of times Cell Y can divide. [2] (b) Outline how Cell X is able to maintain its telomere length. [3] (c) With reference to Fig 5, explain how the change in telomere length resulted in Cell Y* after M2. [2]   (d) Describe the importance of centromeres in cell division. [2] [Total:13]