2016 RVHS H2 Biology Prelims Paper 3 Answers

River Valley High School Pg 1 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION II CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER H2 BIOLOGY 9648/03 Paper 3 Application Paper 20 Sep 2016 2 hours Additional Materials: Answer Paper READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions in the spaces provided on the question paper. Section B Answer all question on the answer paper provided. 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 appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is gi ven in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 / 13 2 / 13 3 / 14 4 / 12 Section B 5 / 20 Total / 72 _____________________________________________________________________ This Question Paper consists of 16 printed pages.

River Valley High School Pg 2 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination I Section A (80 marks) Answer all the questions in this section. 1 The coat colour of Norwegian cattle is mainly determined by the distribution of two pigments: red and black. Both pigments ar e produced by the action of the enzyme tyrosinase, in cells called melanocytes. A low level of activity of the enzyme leads to the production of red pigment, while a high activity of the enzyme produces black pigment. The activity of the enzyme is increased by the melanocyte stimulating hormone (MSH), which binds to the MSH receptor. The receptor is encoded by the gene at E locus, which has three alleles, E D, EA and e. ED and EA each encodes a receptor with different activity. No receptor is produced by the recessive allele, e. Alleles ED and EA differs by a single base substitution; while alleles e and EA differs by a single base deletion. (a) Explain how a mutation at EA allele may result in e allele. [3] 1. This results in a nonsense mutation; 2. by changing reading frame of codons on mRNA; Accept: frameshift mutation 3. This give rise to a stop codon; 4. thus premature termination of translation; 5. Resulting in a truncated polypeptide; 6. thus no protein produced;

River Valley High School Pg 3 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination I DNA was extracted from the frozen semen of six bulls with different genotypes at the E locus. The DNA from each animal was separately digested with two different restriction enzymes, P and Q. The products of each digestion were separated on a gel and the banding pattern shown in Fig. 1.1. Fig. 1.1 (b) (i) Explain why the banding pattern from the same genotype are different when a different restriction enzyme is used. [2] 1. Different restriction enzymes recognizes different restriction sites; 2. thus cuts the DNA at different positions; 3. resulting in different number; 4. and length of restriction fragments; (ii) Explain the role of marker DNA. [2] 1. Comprises a collection of DNA fragments; 2. Compare marker DNA with DNA fragements;; 3. to measure length / size / base pair of DNA fragment;

River Valley High School Pg 4 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination I (iii) State which genotype(s) can be identified by using each of the two restriction enzymes. [2] P: ee;; Reject: multiple listing Q: EDED;; Reject: multiple listing Bovine somatotropin (BST) is an animal hormone used to increase milk production in dairy cows. BST is naturally produced in the cow pituitary gland in small quantity and is used to regulate metabolic processes. With the advent of biotechnology, BST gene can be cloned in Escherichia coli. The bacteria are grown in bioreactors to produce BST, which is purified to produce hormone for injection. Fig. 1.2 shows the plasmid map of the plasmid BGH1, used for transformation of BST gene into E.coli. Sal 1 restriction enzyme was used to cut the pBGH1 plasmid for insertion of BST gene. Fig. 1.2 (c) (i) Describe the natural role of Sal 1 restriction enzyme. [2] 1. To protect bacteria; 2. by cutting foreign DNA;; 3. Such as that of invading viruses; (ii) Explain how AmpR gene facilitates BST gene cloning. [2] 1. Functions as a selectable marker; 2. to identify transformed bacteria / bacteria that took up pBGH1 plasmid; 3. Amp R gene codes for (β-lactamase) enzyme; 4. that inactivate / breakdown ampicillin / allow bacteria to survive (in ampicillin); [Total: 13]

River Valley High School Pg 5 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination I 2 Omega-3 fatty acids are polyunsaturated fats that are often marketed as health supplements to prevent cholesterol deposits in arterial walls. In the wild, omega-3 fatty acids are produced by marine algae and accumulate in small fishes that feed on them. These small fishes are then fed to farmed fishes to increase their omega-3 fatty acid content. Farmed fishes high in omega-3 fatty acids serve as a good source for omega-3 fatty acid extraction for the health supplement industry. A new method to produce omega-3 fatty acids involves insertion of seven genes of the marine algae into oilseed plant, Camelina sativa. The resulting seeds contain as much as 200 milligrams of omega-3 fatty acids in a single tablespoon of ‘fish oil’ extracted. Currently, this ‘fish oil’ is fed to farmed fishes, in replacement of small fishes. The effect of human consumption of ‘fish oil’ from genetically modified C. sativa seed pods is still under investigation. Fig. 2.1 Source: http://www.independent.co.uk/news/science/new-gm-cereal-crop-produces-fish-oil-in-its-seeds- 10372772.html (a) A Ti plasmid containing the seven genes from marine algae is constructed and reintroduced into A. tumefaciens before infecting C. sativa plant cells. Describe the properties of Ti plasmids that make them suitable as vectors in this process. [2] 1. Ti plasmids contain T-DNA region which can be integrated into plant chromosome;; 2. Ti plasmids are small allowing it to be taken up by C. sativa cell;; 3. Ti plasmids contain origin of replication, allows independent replication of plasmid and the inserted genes;; 4. Ti plasmids contain selectable marker allows for identification of transformed C. sativa cells;; 5. Ti plasmids have multiple restriction sites, to allow introduction of genes;; Any 2

River Valley High School Pg 6 of 16 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination I (b) Suggest why crop plants like C. sativa are better candidates for genetic modification than fishes. [2] 1. C. sativa cells are totipotent / can give rise to a whole plant;; 2. Genetic manipulation can be performed on any somatic/plant cell (to generate crop plants with new traits);; 3. To create GM fishes, genes need to be injected into nucleus of fertilised egg;; (c) (i) With reference to Fig 2.1 , suggest two benefits of using genetically modified C. sativa as an omega-3 fatty acid source for farmed fishes. [2] 1. Increase the quality of farmed fishes as fishes will be rich in omega-3 oil;; 2. Possibility of mass production of genetically modified C. sativa, reduces need for fishing, less disturbance to marine food chain;; 3. More sustainable source of omega-3 fatty acids, seeds produced can be used to plant new genetically modified C. sativa;; 4. Easy storage of seed pods as compared to live feed;; 5. Reduces pos