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  • 1. AQA Unit 5 Biology DNA and Gene Technology – and Essays
  • 2. Gene cloning, transfer and Gene therapy No specific examples required, the emphasis is on understanding the principles involved Examples such as production of AAT by sheep are now outdated Still need to learn about roles of enzymes and methods involved in gene/DNA cloning by in vivo and in vitro techniques Use of recombinant DNA technology to benefit humans Evaluate the effectiveness of gene therapy
  • 3. DNA and gene technology PCR still a problem for many – learning by rote but without understanding? HSW – appreciating the methodology – not just a recipe Much of factual content very familiar (to teachers) But a lot of AO2 and AO3 (HSW) associated with – Candidates should be able to • interpret data relating to use of recomb. DNA tech. • evaluate ethical, moral and social issues of its use in agriculture, industry and medicine • balance humanitarian with opposition from environmentalists and anti-globalisationists
  • 4. Balance between humanitarian aspects and others – GM maize on additional sheets The ‘pros’ and ‘cons’ – looking for more than one side of the argument – not just ‘good’ or ‘bad’
  • 5. Base sequence of a gene,_Restric tion_Mapping_&_Automated_DNA_Sequencing_Ii Isolate gene and clone – e.g. by using PCR Create smaller fragments of the gene – with known position in gene – using restriction enzymes Leading to restriction mapping of sections of the gene Then determine base sequences of each fragment – DNA sequencing – e.g. Sanger method
  • 6. Using DNA probes Screening – people as carriers – patients for oncogenes - preimplantation embryos Screening – people as carriers – patients for oncogenes - preimplantation embryos Retinoblastoma – and a tumour suppressor gene – additional sheet
  • 7. Genetic fingerprinting Repetitive, non-coding base sequences – STRs introns, VTRs Often called ‘junk’ DNA – is it?? Inherited, in pairs, mutate – so different alleles – unique combination for each person Can be used for identification of cells, people, populations, species Additional sheets
  • 8. Essay Essay – 25 marks – choice of two titles – marked + as present AQA Spec A Marking based on descriptors, not marking points This is a synoptic exercise – to demonstrate ability to bring together relevant information – showing a grasp of underlying concept(s) within a title Approx. 5 paragraphs that draw on a range of examples from across two years of study Making sure they address the theme of the essay – e.g. the ‘negative feedback’ essay recently
  • 9. The essay The essay is intended to provide candidates with the opportunity to demonstrate: • the ability to express ideas clearly and logically in continuous prose • synoptic skills by selecting and bringing together relevant principles and concepts from different areas of biology • evidence of study at greater breadth or depth, in keeping with performance at A* 9
  • 10. The main features of the essay question • Builds on skills that should have been developed in answering the longer structured questions at AS • The question offers a choice of two titles and is designed for completion in approximately 40 minutes • It is marked by a series of descriptors which reflect Evidence of knowledge and understanding in keeping with an A-level course of study Selection of material relevant to the title, drawn from different areas of the specification Ability to present an argument coherently and logically, using appropriate biological language. 10
  • 11. Candidate 1. If blood glucose concentration is too high; • specific receptors plasma membrane of pancreas cells detect this and cells release insulin into the blood, • binds to specific receptors on effector cells – in liver, • causes more glucose carrier proteins to become active/ be recruited in cell surface membrane, • so more glucose diffuses into cells, by facillitated diffusion, • so more substrate for enzymes that make glycogen, • this removes glucose from solution, maintaining diffusion gradient – so glucose leaves blood and lowers blood conc.
  • 12. Candidate 2. If blood glucose concentration is too high; • receptors on cell surface of pancreas cells detect this and cells release insulin into the blood, • binds to receptors on effector cells – in liver, • so more glucose diffuses into cells, by facillitated diffusion, • so more enzyme activity to make glycogen, • so glucose leaves blood and lowers blood conc, • this causes pancreas cell to release less insulin – negative feedback. Both candidates had four other good examples – and each paragraph was of the same quality as the one shown. One candidate scored 10/12 for content and the other 14/16. Which one and why?
  • 13. Not a showcase for detailed, extra knowledge on just one or two topics Practice – old AQA titles appropriate – no introduction or conclusion required A* - only 16 content marks if evidence of study beyond the specification – i.e. they’ve read something beyond the spec Note – not for writing pages and pages of very advanced content on one topic A* - not worth extra tuition/lessons – encourage able students to read popular science journals or newspaper articles – critically!