RI Nov 13 H2P3 ans

Raffles Institution Nov 2013 (H2 Biology) Paper 3 (for 9744 syllabus) 2017 Nov 2013 H2 Bio Paper 3 . N13P3Q1 (a) State two other ways in which RFLP can be used as a biological tool. [2] RFLP can be used in the analysis of 1. detection of disease e.g. sickle cell anaemia; 2. DNA fingerprinting* in forensics / paternity testing (b) (i) Complete Table 1.1 to show the number of restriction sites and the size of the fragments resulting from digestion of each 15kb DNA molecule, for the three samples. [2] Table 1.1 BamHI EcoRI BamHI and EcoRI Number of restriction sites 1 2 3 Size of fragments / kb 4,11 2,3,10 1,2,3,9 (ii) Using the information from Fig. 1.1 and Table 1.1, it is possible to map the 15kb length of DNA for BamHI and EcoRI. The restriction map for BamHI is shown in Fig. 1.2. Complete the restriction map in Fig. 1.3 for both BamHI and EcoRI, by adding the positions of the EcoRI restriction sites. Indicate the size, in kb, of each fragment. [2] Teacher’s comments: The 2 answers below cannot get the 10kb fragment, hence incorrect. (c) Outline why gel electrophoresis separates DNA fragments. [4] 1. Negatively-charged DNA*; 2. migrates towards the positive electrode/anode when subjected to an electric field / current; 3. Fragments migrate through agarose gel matrix, made up of a meshwork of polysaccharides ; which impedes movement of longer fragments more than shorter fragments; 4. Longer fragments migrate slower compared to shorter fragments;

Raffles Institution Nov 2013 (H2 Biology) Paper 3 (for 9744 syllabus) 2017 (d) Outline the process of DNA hybridization that allows the RFLP pattern for a parti cular gene to be visualized [5] To detect the RFLP pattern of a gene, after the DNA from is digested with restriction enzyme and the digested DNA separate using gel electrophoresis 1. ds DNA is denatured / made single -stranded and by alkaline / NaOH solution and transferred to a nitrocellulose membrane; exactly the same position as they were in the gel 2. The nitrocellulose membrane incubated with a radioactive single stranded DNA probe *, that is complementary in sequence* to part of the target sequence / gene. 3. DNA fragments containing this part of the target sequence will hybridise to the probe by complementary base-pairing*; 4. After hybridisation, membrane is washed to remove any unhybridised probes. 5. Using Autoradiography/X-ray film* over the membrane , the banding pattern can be visualised. (The radioactivity of the bound probes exposes the film to form an image corresponding to the bands that have base-paired to the probe.) N13P3Q2 2 (a) (i) Cytosine is a pyrimidine. Name the other pyrimidine. [1] Thymine* (ii) Suggest how meth