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outdated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
http://www.wepapers.com/Papers/58138/Gel_Electrophoresis,_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
www.humangenetics.org.uk/.../Scottish%20PGD%20Servicev2.ppt
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!