AQA Unit 5 BiologyAQA Unit 5 Biology

DNA and Gene Technology DNA and Gene Technology – and Essays– and Essays

Gene cloning, transfer and Gene therapyGene cloning, transfer and Gene therapy

No specific examples required, the emphasis is on No specific examples required, the emphasis is on understanding the principles involvedunderstanding the principles involved

Examples such as production of AAT by sheep are now Examples such as production of AAT by sheep are now outdatedoutdated

Still need to learn about roles of enzymes and methods Still need to learn about roles of enzymes and methods involved in gene/DNA cloning by involved in gene/DNA cloning by in vivo in vivo and and in vitro in vitro techniquestechniques

Use of recombinant DNA technology to benefit humansUse of recombinant DNA technology to benefit humans

Evaluate the effectiveness of gene therapyEvaluate the effectiveness of gene therapy

DNA and gene technologyDNA and gene technology

PCR still a problem for many – learning by rote butPCR still a problem for many – learning by rote but

without understanding? without understanding?

HSW – appreciating the methodology – not just a recipe HSW – appreciating the methodology – not just a recipe

Much of factual content very familiar (to teachers) Much of factual content very familiar (to teachers)

But a lot of AO2 and AO3 (HSW) associated with –But a lot of AO2 and AO3 (HSW) associated with –

Candidates should be able toCandidates should be able to

• interpret data relating to use of recomb. DNA tech.interpret data relating to use of recomb. DNA tech.

• evaluate ethical, moral and social issues of its use evaluate ethical, moral and social issues of its use in agriculture, industry and medicinein agriculture, industry and medicine

• balance humanitarian with opposition from balance humanitarian with opposition from environmentalists and anti-globalisationists environmentalists and anti-globalisationists

Balance between humanitarian aspects and others –Balance between humanitarian aspects and others –

GM maize on additional sheetsGM maize on additional sheets

The ‘pros’ and ‘cons’ – looking for more than one sideThe ‘pros’ and ‘cons’ – looking for more than one side

of the argument – not just ‘good’ or ‘bad’of the argument – not just ‘good’ or ‘bad’

Base sequence of a geneBase sequence of a genehttp://www.wepapers.com/Papers/58138/Gel_Electrophoresis,_Restriction_Mapping_&_Automated_DNA_Sequencing_Ii

Isolate gene and clone – e.g. by using PCR Isolate gene and clone – e.g. by using PCR

Create smaller fragments of the gene – with knownCreate smaller fragments of the gene – with known

position in gene – using restriction enzymesposition in gene – using restriction enzymes

Leading to restriction mapping of sections of the gene Leading to restriction mapping of sections of the gene

Then determine base sequences of each fragment –Then determine base sequences of each fragment –

DNA sequencing – e.g. Sanger methodDNA sequencing – e.g. Sanger method

Using DNA probesUsing DNA probes

Screening – people as carriers – patients for oncogenesScreening – people as carriers – patients for oncogenes

- preimplantation embryos- preimplantation embryos

www.humangenetics.org.uk/.../Scottish%20PGD%20Servicev2.ppt

Screening – people as carriers – patients for oncogenesScreening – people as carriers – patients for oncogenes

- preimplantation embryos- preimplantation embryos

Retinoblastoma – and a tumour suppressor gene –Retinoblastoma – and a tumour suppressor gene –

additional sheetadditional sheet

Genetic fingerprintingGenetic fingerprinting

Repetitive, non-coding base sequences – STRs introns,Repetitive, non-coding base sequences – STRs introns,

VTRs VTRs

Often called ‘junk’ DNA – is it??Often called ‘junk’ DNA – is it??

Inherited, in pairs, mutate – so different alleles – uniqueInherited, in pairs, mutate – so different alleles – unique

combination for each personcombination for each person

Can be used for identification of cells, people,Can be used for identification of cells, people,

populations, species populations, species

Additional sheets Additional sheets

Essay Essay

Essay – 25 marks – choice of two titles – marked Essay – 25 marks – choice of two titles – marked ++ as as

present AQA Spec A present AQA Spec A

Marking based on descriptors, not marking pointsMarking based on descriptors, not marking points

This is a This is a synopticsynoptic exercise – to demonstrate ability to exercise – to demonstrate ability to

bring together relevant information – showing a graspbring together relevant information – showing a grasp

of underlying concept(s) within a titleof underlying concept(s) within a title

Approx. 5 paragraphs that draw on a range ofApprox. 5 paragraphs that draw on a range of

examples from across two years of studyexamples from across two years of study

Making sure they address the theme of the essay – e.g.Making sure they address the theme of the essay – e.g.

the ‘negative feedback’ essay recentlythe ‘negative feedback’ essay recently

99

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*

1010

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 reflectEvidence of knowledge and understanding in keeping with an A-level course of studySelection of material relevant to the title, drawn from different areas of the specificationAbility to present an argument coherently and logically, using appropriate biological language.

Candidate 1Candidate 1. If blood glucose concentration is too high;. If blood glucose concentration is too high;

• specific receptors plasma membrane of pancreas cells specific receptors plasma membrane of pancreas cells detect this and cells release insulin into the blood,detect this and cells release insulin into the blood,

• binds to specific receptors on effector cells – in liver,binds to specific receptors on effector cells – in liver,

• causes more glucose carrier proteins to become active/ causes more glucose carrier proteins to become active/ be recruited in cell surface membrane,be recruited in cell surface membrane,

• so more glucose diffuses into cells, by facillitated so more glucose diffuses into cells, by facillitated diffusion,diffusion,

• so more substrate for enzymes that make glycogen,so more substrate for enzymes that make glycogen,

• this removes glucose from solution, maintaining this removes glucose from solution, maintaining diffusion gradient – so glucose leaves blood and lowers diffusion gradient – so glucose leaves blood and lowers blood conc.blood conc.

Candidate 2Candidate 2. If blood glucose concentration is too high;. If blood glucose concentration is too high;

• receptors on cell surface of pancreas cells detect this receptors on cell surface of pancreas cells detect this and cells release insulin into the blood,and cells release insulin into the blood,• binds to receptors on effector cells – in liver, binds to receptors on effector cells – in liver, • so more glucose diffuses into cells, by facillitated so more glucose diffuses into cells, by facillitated diffusion,diffusion,• so more enzyme activity to make glycogen,so more enzyme activity to make glycogen,• so glucose leaves blood and lowers blood conc,so glucose leaves blood and lowers blood conc,• this causes pancreas cell to release less insulin – this causes pancreas cell to release less insulin – negative feedback.negative feedback.

Both candidates had four other good examples – and Both candidates had four other good examples – and each paragraph was of the same quality as the one each paragraph was of the same quality as the one shown. One candidate scored 10/12 for content and the shown. One candidate scored 10/12 for content and the other 14/16. Which one and why?other 14/16. Which one and why?

Not a showcase for detailed, extra knowledge on justNot a showcase for detailed, extra knowledge on just

one or two topics one or two topics

A* - only 16 content marks if evidence of study beyondA* - only 16 content marks if evidence of study beyond

the specification – i.e. they’ve read something beyond the specification – i.e. they’ve read something beyond

the spec the spec

A* - not worth extra tuition/lessons – encourage ableA* - not worth extra tuition/lessons – encourage able

students to read popular science journals or students to read popular science journals or

newspaper articles – critically! newspaper articles – critically!

Practice – old AQA titles appropriate – no introductionPractice – old AQA titles appropriate – no introduction

or conclusion required or conclusion required

Note – not for writing pages and pages of veryNote – not for writing pages and pages of very

advanced content on one topic advanced content on one topic