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 s