AQA A Level Biology Paper 1 June 2018, Exams of Advanced Education

Download AQA A Level Biology Paper 1 June 2018 and more Exams Advanced Education in PDF only on Docsity! AQA A Level Biology Paper 1 June 2018 When preparing the cells for observation the scientist placed them in a solution that had a slightly higher (less negative) water potential than the cytoplasm. This did not cause the cells to burst but moved the chromosomes further apart in order to reduce the overlapping of the chromosomes when observed with an optical microscope. Suggest how this procedure moved the chromosomes apart. [2 marks] - water moves into the cells/ cytoplasm by osmosis cell/ cytoplasm gets bigger The dark stain used on the chromosomes binds more to some areas of the chromosomes than others, giving the chromosomes a striped appearance. Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas.[1 mark] - differences in base sequence What is a homologous pair of chromosomes? [1 mark] - chromosomes that carry the same genes Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of the human DNA. [2 marks] - (Prokaryotic DNA) is 1. Circular (as opposed to linear) 2. Not associated with proteins/ histones 3. Only one molecule/ piece of DNA Describe the method the student would have used to obtain the results in Figure 3. Start after all the cubes of potatoes have been cut. Also consider variables he should have controlled. [3 marks] - Method to ensure all the cut surfaces of the eight cubes are exposed to the sucrose solution method of controlling temperature method of drying cubes before measuring measure of mass of tubes at stated time intervals What is meant by 'species richness'? [1 mark] - (a measure of)the number of (different) species in a community Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. [2 marks] - reduces activation energy due to bending bonds Lyxose binds to the enzyme. Suggest a reason for the difference in the results shown in Figure 5 with and without lyxose. [3 marks] - (binding) alters the treaty structure of the enzyme; (this causes) active site to change (shape) (so) more (successful) E-S complexes form (per minute) OR E-S complexes form more quickly OR Further lowers the activation energy The genetic code is described as degenerate. What is meant by this? [1 mark] - more than one codon codes for a single amino acid The scientists tested their null hypothesis using the chi-squared statistical test. After 1 cycle their calculated chi-squared value was 350. The critical value at P=0.05 is 3.841