VJC_H3_BIO_Answers_2017

1    VICTORIA JUNIOR COLLEGE BIOLOGY DEPARTMENT JC2 PRELIMINARY EXAMINATIONS 2017 Higher 3 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 9815/01 25 September 2017 Additional Materials: Answer Paper 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your CLASS/ 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. Section A Answer all questions. Section B Answer three out of four questions. Section C Answer the question. At the end of the examinations, 1. Fasten all your work securely; 2. Circle the number of the section B question you have answered in the grid opposite. The number of marks is given in brackets [ ] at the end of each question or part question. This paper consists of 10 printed pages, including the cover page. For Examiner’s Use Section A 1 2 3 4 5 Section B 6 7 8 9 Section C 10 Total

2    Section A Answer all questions in this section. 1 (a) A genetic study of coat ty pe in purebred dogs has identified a mutation in the keratin gene KRT71, associated with the curly fur phenotype in some breeds. Keratin is known to be abundant in cystei ne. Suggest how a single mutation in KRT71 can lead to this curly fur phenotype. [2]  Mutation is likely to be a missense mutation that leads to a frameshift in the nucleotide sequence;  Leading to an unusually high number of codons specifying for the amino acid cysteine in the primary structure of altered keratin;  Cysteine has a sulfur-containing functional group/ thiol group;  The abundant number of cysteines (in altered hair keratin) allows numerous disulphide bridges to form between cysteines, resulting in curly hair; (b) Mandy decided that she wanted to loosen t he curls in her poodle’s fur. She first hosed her poodle down with water and then applied an ammonium thioglycolate solution (a reducing agent) as she roll ed her poodle’s fur around larger-diameter rollers. Next, she applied h