2018 VJC H2 Biology Prelims Paper 3 Questions

1 VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2018 NAME : ____________________________________ CT CLASS : ____________________________________ H2 BIOLOGY 9744/03 Paper 3 Long structured and free-response 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. Section A Answer all questions in the spaces provided on the question paper. Section B Answer any one question. 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 the appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 13 printed pages and 1 blank page. For Examiner’s Use 1 2 3 Section B Total

2 Section A Answer all the questions in this section. 1 Pneumonia is disease caused by the gram-positive pneumococcal bacteria. Pneumococcal infections result in an infl ammatory condition of the lung affecting primarily the small air sacs known as al veoli. Hence, the symptoms of pneumonia include dry cough, chest pain, fever, and difficulty in breathing. Pneumonia affects approximately 450 millio n people globally (7% of the population) and results in about 4 million de aths per year. Up to 40% of these infections were caused by pneumococcal bacteria that were resistant to at least one antibiotic. Due to the severity of pneumonia and the rise in antibiotic resistance among bacteria, vaccines have been developed to protect individuals against the disease. (a) Evaluate the effectiveness of vaccines agains t the rise of antibiotic-resistant strains of pnemococcal bacteria. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………….… [4] With the continuing threat of antibiotic resistance, bacteriophage therapy is employed as a mean to treat bacterial infections. (b) Describe how a typical T4 bacteriophage can work against an antibiotic-resistant bacterium. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………….…[3]

3 (c) A subset of the bacteriophage population, termed as “superspreaders”, is observed to release substantial amounts of intac t, transformable bacteri a plasmid DNA along with the release of its progeny from the host. These plasmid DNA molecules, however, are not found within the nucleocapsid of the bacteriophages. These “superspreaders” are deemed to hav e the potential to promote antibiotic resistance among bacteria. The use of antibiotics instead of decreasing numbers appears to increase the numbers of antibiotic resistance bacteria. (i) Using the information given, describe how a bacterium could have acquired antibiotic resistance due to the release of such plasmid DNA. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………….…[2] (ii) Suggest how this could lead to an incr ease in the proportion of bacteria with antibiotic resistance in the population. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………….[3]

4 T4 bacteriophages generally contai n phage-encoded endonucle ases. The phage- encoded endonucleases serve to hydrolyse the bacteria chromosome. It is hypothesised that the “superspreaders” may lack hydrolytic endonucleases, hence are able to release intact plasmid DNA during exit from the host cell. A group of researchers decided to carry out an experiment on two strains of “superspreaders”, namely SUSP1 and SUSP2, as well as T4 bacteriophage. The 3 types of viruses are then exposed to Escherichia coli bacteria containing a chromosomal DNA molecule and an extr a-chromosomal 130bp plasmid DNA molecule. In the control setup, the bacteria are not exposed to any virus. Fig.1.2 shows the result of the experiment. Fig. 1.2 (d) Briefly comment on the validity of the hypothesis based on the results shown in Fig. 1.2. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………...……………………………….… [3]

5 To further confirm their hypothesis, researchers decide to amplify the genome of the three viruses and run a gel electrophoresis. (e) As a good Biology student, name and descri be a procedure that the researchers should undertake to determine the pres ence or absence of the hydrolytic endonucleases in the “superspreaders”. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………...……………………………………………………………………………….… [4] With climate change, environmental scientists predict that there will be a surge in the emergence of new viral and bacterial infect ious diseases to the current human population. (f) Besides mutation, suggest how the environmental scientists’ prediction might come true. ………………………………………………………………………………………………….. …………………………………………………………………………………………….… [1] [Total: 20]

6 2 The mitotic cell cycle consists of a sequence of carefully orchestrated events that a cell passes through between one division and the next. It is tightly regulated to ensure that cells will only undergo division when conditions are optimal. Fig. 2.1 shows the mitotic cell cycle. Fig. 2.1 (modified from https://mrrittner.weebly.com/unit-4-cell-cycle.html) (a) (i) On Fig. 2.1, label and name two critical positions where a cell can be regulated in the mitotic cell cycle. [2] (ii) Explain the significance of the critical positions labelled in (a) (i) to the regulation of the cell cycle. Position 1 …………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. Position 2 …………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………….…… ………………………………………………………………………………………….… [4]

7 Dysregulation of cell cycle leads to cancer. Skin cancer cells may be grown in cult ure and examined using the technique of immunofluorescence in which antibodies are used to attach fluorescent dyes to specific molecules within the cells. Fig. 2.2 is an immunofluorescent light micrograph of skin cancer cells. There are two cells in the process of nuclear division, one of which has areas stained with two different fluorescent dyes, labelled A and B on Fig. 2.2. Fig. 2.2 (b) Identify the two areas labelled A in the dividing cell in Fig. 2.2 and outline their function. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………