2016 VJC H2 Biology Prelims Paper 3 Questions

1 VICTORIA JUNIOR COLLEGE BIOLOGY DEPARTMENT JC2 PRELIMINARY EXAMINATIONS 2016 Higher 2 VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9648/03 Paper 3 19 September 2016 Additional Materials: Answer Booklet/ Paper 2 Hours READ THESE INSTRUCTIONS FIRST Write your CT GP/ INDEX NO. and name on all the work you hand in. Write in dark blue or blue pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use any staples, paper clips, highlighters, glue or correction fluid. Answer all questions. At the end of the examination, fasten all your work securely together. The intended number of marks is given in brackets [ ] at the end of each question. This document consists of 16 printed pages. 1 5 S For Examiner’s Use Section A 1 2 3 Planning Question 5 Total

2 Answer all questions Question 1 (a) The bacterial plasmid, pBR322, was used as a ve ctor for Gene X as shown in Fig. 1.1 below. Gene X was inserted in the BamHI restriction site. pBR322 also contain the EcoRI and HpaI restriction sites. The target sites for these restriction enzymes are shown in the table below. The line s drawn in each sequence show where the enzyme cuts the DNA molecule.   (i) With reference to Fig. 1.1, explain how two properties of plasmid pBR322 allow it to be used as a vector. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2] EcoRI site EcoRI site

3 (ii) Outline the steps taken to produce the recombinant plasmid shown in Fig. 1.1. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2] (iii) Explain the disadvantage that would arise if gene X was to be inserted into the HpaI restriction site instead of the BamHI site. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2] (b) Calcium chloride heat shock treatment was then used to introduce the recombinant plasmid into Escherichia coli . However, the process of creating recombinant plasmids is typically not 100% efficient. Often, a mixture of re- annealed plasmid and re-annealed DNA is produced along with the recombinant plasmid. These may be taken up by the bacteria as well. This necessitates the process of selecting for the bacteri a that have successfully taken up the recombinant plasmid. As such, the bacte ria was first plated onto a nutrient agar plate containing ampicillin. Replica pl ating was subsequently carried out onto a nutrient agar plate containing tetracycline. Bacterial growth on both plates is shown in Fig. 1.2.

4 With reference to Fig 1.2, (i) Circle the colonies that were successf ully transformed with the recombinant plasmid. [ 1 ] (ii) Account for the difference in colony numbers in Plate A and B. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [3] (c) In a separate cloning experiment, the same plasmid pBR322 was used to introduce another gene, Gene Y, into a bat ch of E.coli cells. Fig. 1.3 shows the results of plating the transformed E.coli cells onto an agar plate with the appropriate substances. Fig. 1.3

5 (i) Explain why the colonies differ in colours in Fig. 1.3. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [4] (ii) Suggest why replica plating was not necessary in this experiment. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [1]

6 (d) In another cloning experiment, another plasmid pBR33 was used to introduce Gene Z into a different strain of E.coli bacteria. Gene Z was inserted into one of the three selection markers found in pBR33 – neomycin resistance gene, kanamycin resistance gene and streptomycin resistance gene. The bacteria were then plated onto nutrient agar plate containing neomycin. Replica plating was subsequently carried out ont o nutrient agar plate containing streptomycin. Bacterial growth on the two plates is shown in Fig. 1.4 below. Fig. 1.4 Account for the results obtained in Fig. 1.4. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ……………………………………………………………………………………………… [3] [Total 18] Replica plate containing Streptomycin (Plate S) Plate containing Neomycin (Plate N)

7 Question 2 Explain why two primers are used for polymerase chain reaction. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ………………………………………………………………………………………….……… [2] Duchenne muscular dystrophy is a genetic disease in which t here is a progressive loss of muscle mass, leading to physical weakness, difficulty in standing and walking, and eventually paralysis and death. Early symptoms of the di sease can only be observed between the ages of 2 and 3 in most patients. A group of doctors and medical biologists discovered a RFLP marker, found on the sa me chromosome as the disease gene, which can be used in the screening of the disease during pregnancy. To investigate the effective of the RFLP marker in disease screening, samples of DNA were obtained from a family known to have t he disease. The RFLP locus was isolated and amplified using polymerase chain reaction, which was then mixed with BamHI restriction enzymes. The pedigr ee tree of the family and resu lts of gel electrophoresis are shown in Fig. 2.1. Fig. 2.1 (a) With reference to Fig. 2.1, (i) state the mode of inheritance of the Duchenne muscular dystrophy. ………………………………………………………………………………………….……… [1]

8 (ii) explain why there are different fragment lengths after restriction digest. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ………………………………………………………………………………………….……… [3] (iii) Explain the difference in the band patte rns between the father and the daughter. ………………………………………………