SNAB T2 Teaching scheme
Topic 2 Genes and health
This teaching scheme is divided into three parts.
 Introduction.
 Road map: a suggested route through Topic 2.
 Guidance notes for teachers and lecturers. These include a commentary that runs
parallel with the student book with hints and tips on teaching and references to the
associated activities.
There are more detailed notes about individual activities in the teacher/lecturer sheets
accompanying most activities.
Introduction
The Road map starting on page 2 is a suggested route through Topic 2.
The learning outcomes are numbered as in the specification.
Here are notes a route through the topic if two teachers/lecturers are sharing a group for
Topic 2. The first teacher starts introduces the topic context, making it clear that the problem
is a faulty protein in the membrane. The first teacher looks at the effects of this on the lungs,
while the second teacher is considering the effect on the digestive and reproductive system.
The first teacher would complete sessions 2 / 3 / 6 / 7 / 8 / 9 / 17 / 18 /19 / 20 / 21. The
second teacher would complete sessions 4 / 5 / 10 / 11 / 12 / 13 / 14 / 15 / 16 This covers
protein structure before enzymes. The first teacher has more sessions, so if they have done
the introduction the second teacher may need to complete genetic screening (sessions 20
and 21) at the end of their sequence.
Note that learning outcome 17 Explain how the expression of a gene mutation in people
with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and
reproductive system appears in several places throughout the table that starts on page 2.
There is an AS summary chart map at the end of the guidance notes. This shows where
concepts are introduced and revisited in later topics. (Some students will have studied cystic
fibrosis and its effects, and the associated ethical dilemmas, at GCSE.)
It is assumed that each session is approximately an hour in length. There are more activities
than can be done in the time available in most centres, so select a balanced collection
according to your and your students’ interests, and the time and resources available. Some
activities are labelled ‘Core’. Core activities contain experimental techniques included in the
specification, and may appear in questions on the unit exam for this topic. These learning
outcomes are in bold in the specification, and in the Read map below. They are underlined
in the Guidance notes below. In the Road map, activities are in italics if there is an
additional activity covering the same material more directly. Choose which activities
students complete, and substitute activities when appropriate.
The Core practicals, and any other practicals completed by students, can be used to assess
practical biological skills as part of the Unit 3 coursework assessment.
There are various activities – particularly the interactive tutorials associated with some of
the activities – which could be completed by students outside of class time. These activities
are shown in the lower half of each ‘Possible activities’ box.
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SNAB T2 Teaching scheme
Road map: a route through Topic 2 Genes and health
Session
Areas to be covered
Possible activities
Introductory presentation (Interactive
tutorial)
Activity 2.1 After the funeral
(A2.01L)
Activity 2.2 Personal CF stories
(A2.02L)
1
GCSE review test (Interactive)
Diffusion and surface area to volume
ratio
2
6 Describe the properties of gas
exchange surfaces in living organisms
(large surface area to volume ratio,
thickness of surface, difference in
concentration) and explain how the
structure of the mammalian lung is
adapted for rapid gaseous exchange.
Activity 2.3 The effect of size on
uptake by diffusion (A2.03L)
(Practical)
Q2.1–Q2.13
17 Explain how the expression of a
gene mutation in people with cystic
fibrosis impairs the functioning of the
gaseous exchange, digestive and
reproductive systems.
Structure of alveoli and SA:V ratio;
properties of gas exchange surfaces
3
6 Describe the properties of gas
exchange surfaces in living organisms
(large surface area to volume ratio,
thickness of surface, difference in
concentration) and explain how the
structure of the mammalian lung is
adapted for rapid gaseous exchange.
Activity 2.4 The structure of alveoli
(A2.04L) (Practical)
Activity 2.5 Alveoli and lung surface
area (A2.05L) (Interactive)
Checkpoint question 2.1
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SNAB T2 Teaching scheme
Session
4/5
Areas to be covered
Possible activities
Protein structure and function
Activity 2.6 Proteins (A2.06L)
(Interactive)
7 Describe the basic structure of an
amino acid (structures of specific
amino acids are not required) and the
formation of polypeptides and proteins
(as amino acid monomers linked by
peptide bonds in condensation
reactions) and explain the significance
of a protein’s primary structure in
determining its three-dimensional
structure and properties (globular and
fibrous proteins and types of bonds
involved in three dimensional
structure).
Membrane structure
6
5 Describe how membrane
structure can be investigated
practically, eg by the effect of
alcohol concentration or
temperature on membrane
permeability.
Transport across membranes
3 Explain what is meant by osmosis in
terms of the movement of free water
molecules through a partially
permeable membrane (consideration
of water potential is not required).
8
Activity 2.7 The fluid mosaic model
(A2.07L)
2 Explain how models such as the fluid
mosaic model of cell membranes are
Build models of membranes
interpretations of data used to develop
scientific explanations of the structure
and properties of cell membranes.
Membrane structure
7
Checkpoint question 2.2
Activity 2.8 Why does the colour
leak out of cooked beetroot?
(Core) (A2.08L)
Activity 2.9 Methods of transport
within and between cells (A2.09L)
(Practical)
4 Explain what is meant by passive
transport (diffusion, facilitated
diffusion), active transport (including
the role of ATP), endocytosis and
exocytosis and describe the
involvement of carrier and channel
proteins in membrane transport.
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SNAB T2 Teaching scheme
Session
Areas to be covered
Possible activities
Membrane transport in epithelial cells
Activity 2.10 CFTR protein and
membrane transport (A2.10L)
(Interactive)
3 Explain what is meant by osmosis in
terms of the movement of free water
molecules through a partially
permeable membrane (consideration
of water potential is not required).
9
4 Explain what is meant by passive
transport (diffusion, facilitated
diffusion), active transport (including
the role of ATP), endocytosis and
exocytosis and describe the
involvement of carrier and channel
proteins in membrane transport.
Enzyme structure and function
10
Checkpoint questions 2.3 and 2.4
8 Explain the mechanism of action and
specificity of enzymes in terms of their
three-dimensional structure and
explain that enzymes are biological
catalysts that reduce activation
energy, catalysing a wide range of
intracellular and extracellular reactions
17 Explain how the expression of a
gene mutation in people with cystic
fibrosis impairs the functioning of the
gaseous exchange, digestive and
reproductive systems.
Enzyme concentration and digestion
11/12
9 Describe how enzyme
concentrations can affect the rates
of reactions and how this can be
investigated practically by
measuring the initial rate of
reaction.
17 Explain how the expression of a
gene mutation in people with cystic
fibrosis impairs the functioning of the
gaseous exchange, digestive and
reproductive systems.
Activity 2.11 Enzyme
concentrations and enzyme
activity (Core) (A2.11L) (Practical)
Checkpoint question 2.5
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SNAB T2 Teaching scheme
Session
13
14/15
16
17
Areas to be covered
Possible activities
DNA structure
Activity 2.13 Extraction of DNA
(A2.13L) (Practical)
10 Describe the basic structure of
mononucleotides (as a deoxyribose or
ribose linked to a phosphate and a
base, ie thymine, uracil, cytosine,
adenine or guanine) and the structures
of DNA and RNA (as polynucleotides
composed of mononucleotides linked
through condensation reactions) and
describe how complementary base
pairing and the hydrogen bonding
between two complementary strands
are involved in the formation of the
DNA double helix.
Protein synthesis
14 Outline the process of protein
synthesis, including the role of
transcription, translation, messenger
RNA, transfer RNA and the template
(antisense) DNA strand (details of the
mechanism of protein synthesis on
ribosomes are not required at AS).
12 Explain the nature of the genetic
code (triplet code only; nonoverlapping and degenerate not
required at AS).
DNA replication
11 Describe DNA replication (including
the role of DNA polymerase), and
explain how Meselson and Stahl’s
classic experiment provided new data
that supported the accepted theory of
replication of DNA and refuted
competing theories.
15 Explain how errors in DNA
replication can give rise to mutations
and explain how cystic fibrosis results
from one of a number of possible gene
mutations
Monohybrid inheritance
Activity 2.12 DNA model (A2.12L)
Activity 2.14 Nucleic acids and
protein synthesis (A2.14L)
(Interactive)
Activity 2.15 Meselson and Stahl’s
experiment on DNA replication
(A2.15L) (Interactive)
Activity 2.16 Reebops (A2.16L)
(Practical)
16 Explain the terms: gene, allele,
genotype, phenotype, recessive,
dominant, homozygote and
heterozygote; and explain monohybrid
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SNAB T2 Teaching scheme
Session
Areas to be covered
Possible activities
inheritance, including the interpretation
of genetic pedigree diagrams, in the
context of traits such as cystic fibrosis,
albinism, thalassaemia, garden pea
height and seed morphology
Checkpoint question 2.6
Monohybrid inheritance
18
16 Explain the terms: gene, allele,
genotype, phenotype, recessive,
dominant, homozygote and
heterozygote; and explain monohybrid
inheritance, including the interpretation
of genetic pedigree diagrams, in the
context of traits such as cystic fibrosis,
albinism, thalassaemia, garden pea
height and seed morphology
Gene therapy
19
21
Activity 2.18 Gene therapy – another
side to the story (A2.18L)
18 Describe the principles of gene
therapy and distinguish between
somatic and germ line therapy.
Genetic screening
20
Activity 2.17 Inheritance problems
(A2.17L)
Activity 2.19 Genetic screening
(A2.19L)
19 Explain the uses of genetic
screening: identification of carriers,
preimplantation genetic diagnosis and
prenatal testing (amniocentesis and
chorionic villus sampling) and discuss
the implications of prenatal genetic
screening.
20 Identify and discuss the social and
ethical issues related to genetic
screening from a range of ethical
viewpoints.
Genetic screening
Activity 2.20 Passing it on (A2.20L)
20 Identify and discuss the social and
ethical issues related to genetic
screening from a range of ethical
viewpoints.
Class discussion
Activity 2.21 Gene mutation – a
personal story (A2.21L)
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SNAB T2 Teaching scheme
Guidance notes for teachers and lecturers
You could complete these continuing professional development modules before starting
Topic 2: CPD1 A road map for SNAB: Building knowledge and principles through the course
and CPD2 Contextualised biology teaching through storylines.
Introduction and GCSE review
The topic starts by introducing a couple, Claire and Nathan, and the dilemma they face in
deciding whether or not to start a family knowing that Claire’s sister had cystic fibrosis (CF).
A wide range of traditional biology concepts is required to understand the causes and
consequences of cystic fibrosis. The ethical issues faced by the couple as they try to make
the decision are highlighted. Some students will have studied cystic fibrosis and its effects,
and the associated ethical dilemmas, at GCSE.
Teachers or lecturers may be presenting this material to groups containing either a student
with CF or a student who has a close relative or friend who has or had the disease. A great
deal of sensitivity will be needed. It is nearly always best to talk before the session to the
student(s) concerned on a one-to-one basis, and see how they would like it to be handled.
Discussing the topic with students in advance may help you to find out if any of them have
connections with CF. Encourage the student(s) in question to take a positive role within the
group; their experiences can make a valuable contribution to discussions. If it is difficult for a
student, you may need to present the material in a more traditional way as a series of
biological principles.
The sections in the topic address the questions that Claire and Nathan may have asked in
their search for information to help their decision-making. The opening page poses some of
these questions.
On the first spread there is a reference to the initial GCSE review and the GCSE review
test. These cover the main GCSE ideas that students will be expected to draw on during the
topic – lung structure and function, digestion, genetics and enzymes. The test itself is open
access, and it is assumed that it will be completed outside of class time.
The interactive introduction provides an overview of the topic.
Activity 2.1 After the funeral (A2.01L)
This provides an overview of the topic. The play, performed or read as a group activity,
provides the opportunity for some discussion. The play is set in the past when Claire was
younger. Students use the text of the play to produce a mind map summarising the main
issues. This acts as a framework for the topic. Additional notes could be added to this map
as the topic unfolds.
Activity 2.2 Personal CF stories (A2.02L)
These personal stories give further insights into the effect of CF on affected individuals and
their families. This could be used as an alternative to Activity 2.1.
2.1 The effects of CF on the lungs
The basic structure of the lungs and the mechanism of breathing are covered in the GCSE
review. The media archive within the electronic resources contains the lung diagram of
Figure 2.2 with and without labels. Labelling the diagram could be a starting-point. If
students have completed the GCSE review this should be straightforward.
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SNAB T2 Teaching scheme
In CF patients there is a build up of sticky mucus in the airways. An X-ray of the lungs of a
CF patient shows this clearly. There is a CF patient X-ray and CAT scan in the general
weblinks for Topic 2. Photographs of normal and CF-affected lungs and pancreases can
also be found via the weblinks.
There are two major consequences of sticky mucus in the lungs: the first is an increased
chance of infection because the mucus cannot be cleared from the lungs, so pathogenic
bacteria can take hold; the second is the blockage of airways by the mucus. The infection
problem is described in the student book and Q2.1 and Q2.2 are linked to this section. The
blockage of the airways occurs to a greater extent in the later stages of the disease.
The main consequence of airway blockage is a reduction in the effective surface area for
gas exchange. The student book has a Key biological principle box with questions
introducing the importance of a large surface area to volume ratio. This is followed by a
section on the features and properties of gas exchange surfaces. These are complemented
by Activities 2.3 to 2.5.
It may be helpful if the continuing professional development module CPD3 Developing
practical skills is completed by teachers/lecturers before starting practical work with
students.
Activity 2.3 The effect of size on uptake by diffusion (A2.03L)
This provides a practical investigation of the effect of surface area on uptake by diffusion. It
is supported by student book questions Q2.3 to Q2.13, which guide the student through the
ideas.
Activity 2.4 The structure of alveoli (A2.04L)
Students follow the instructions on the activity sheet as they observe slides of lungs. The
activity is an opportunity to introduce the use of an eye-piece graticule and stage
micrometer for measuring. See the Practical support sheet ’Measuring: Size and scale’
(P0.09S). Precision in measuring can be discussed.
Activity 2.5 Alveoli and lung surface area (A2.05L)
In this interactive web-based tutorial, students determine the increase in surface area due to
the presence of alveoli using calculations of volume. Students also examine a
photomicrograph showing a section through lung tissue, and identify features that increase
the efficiency of gas exchange. The interactive tutorial can support students as they
complete the calculations on the activity sheet, it can also be done without the tutorial. This
web-based tutorial could be used instead of Activity 2.4, or could be set as a class
assignment to confirm the ideas covered in Activity 2.4.
Checkpoint question 2.1 can be used as a summary question at the end of this section or as
a revision question later. Answers to Checkpoint questions are given on the snabonline
website; these are only accessible to teachers.
2.2 Why is the CF mucus so sticky?
To answer this question, students need to understand what is happening in epithelial cells
not affected by the disease. Mucus in the lungs is ‘runny’ because of salt and water
transport across the epithelial cells. The mucus is sticky in people with CF; this is due to
disruption caused by a faulty transport protein channel in the surface membrane of the
epithelial cells. Students therefore need to know about the structure and function of
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SNAB T2 Teaching scheme
proteins. They also need to know about membrane structure and methods of transport
across membranes.
A Key biological principle box in the student book relates protein structure to function.
Activity 2.6 is found within this box.
Activity 2.6 Proteins (AS2.06L)
This interactive tutorial describes the basic structure of amino acids and follows the
processes involved in the formation of polypeptides. The student worksheet can be
completed using the student book without the tutorial.
The interactive tutorial does not differentiate between globular and fibrous proteins – this
distinction is made in the student book. Checkpoint question 2.2 requires students to
compare and contrast these two types of protein.
Cell membrane structure
The student book goes on to describe the structure of cell membranes, and considers
evidence for the fluid mosaic model which explains the structure and properties of cell
membranes. These ideas are covered in the interactive tutorial accompanying Activity 2.7.
The information is applied in Activity 2.8. Building a model of the cell membrane may help
students understand the three-dimensional structure of the membrane; plasticine can be
used.
Activity 2.7 The fluid mosaic model (A2.07L)
In this activity students evaluate the evidence for different models explaining the structure
and function of cell membranes.
Activity 2.8 Why does the colour leak out of cooked beetroot? (A2.08L) Core practical
In this core practical, students use beetroot to examine the effect of temperature or alcohol
on cell membranes and relate this to membrane structure. The activity sheet provides
detailed procedures for students to follow. Before starting, students are asked to make a
hypothesis and check that the procedure will test their hypothesis. Prompts help them focus
on various practical and investigative skills.
How so substances pass through cell membranes?
The student book describes diffusion, osmosis, active transport, exocytosis and
endocytosis.
Activity 2.9 Methods of transport within and between cells (A2.09L)
This activity consists of a set of simple experiments or demonstrations for diffusion and
osmosis. There is an interactive simulation of the final experiment using blood in the
Biochemistry support on the snabonline website. Students will not have to do any
calculations using water potentials.
Q2.16 enables students to check their understanding of the different sorts of transport
across membranes.
The student book goes on to identify the types of transport involved in the epithelial cells of
the airways.
Activity 2.10 CFTR Protein and membrane transport (A2.10L)
Chloride and sodium ions move across the membranes in epithelial cells, causing water to
enter or leave the cells by osmosis and thus keeping the mucus lining the epithelial cell
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SNAB T2 Teaching scheme
surfaces runny. The interactive tutorial has an animation showing this. It also demonstrates
how the non-functioning CFTR protein channel causes mucus to be sticky. Students view
the animation and complete the accompanying worksheet. This guides students to an
understanding of the mechanisms of salt and water secretion in the airways, and of what
has gone wrong in people with CF. Ideas presented here were the latest understanding of
the mechanism when the material was written. Reasearch into the mechanisms is ongoing.
2.3 How does cystic fibrosis affect other body systems?
The student book describes how blockage of the pancreatic duct reduces enzyme secretion
into the small intestine; this inevitably has an effect on digestion. To help students
understand the consequences of this reduction in enzyme concentration, the student book
includes a Key biological principle box on mechanisms of enzyme function. Students can
use checkpoint questions 2.3 and 2.4 to produce summary notes on enzyme function before
attempting the practical activity.
Activity 2.11 Enzyme concentrations and enzyme activity (A2.11L) Core practical
This core practical investigates the effect of enzyme concentration on rate of reaction. It
provides an opportunity for students to plan an investigation and develop practical and
investigative skills. The planning sheet includes a checklist of what students need to include
in their plan, together with some suggested methods.
The effects of CF in the reproductive system are described in the student book. The
associated Checkpoint question 2.5 requires students to summarise the effects of CF on the
gas exchange, digestive and reproductive systems.
2.4 How is the CFTR protein made?
Students need to understand how a mutation can result in a faulty protein. The student book
and associated activities describe DNA structure, the genetic code and protein synthesis. At
AS, students only need to know that the genetic code is a triplet code, and be able to outline
the process of protein synthesis. Details of the mechanism of protein synthesis on
ribosomes are not required at AS. Protein synthesis is revisited at A2, where the additional
detail is added.
Activity 2.12 DNA model (A2.12L)
The cut-out model of DNA requires the student to work out the pairing of bases according to
base structure and bonding pattern. These are also explained in the student book. If
constructed correctly the model will form a double helix.
Activity 2.13 Extraction of DNA (A2.13L)
Students extract DNA from onions. This is an easy procedure and the result is always
impressive. The DNA is visible largely due to the histone proteins associated with it. There
is a diagram to show the packaging of DNA in Topic 3. The size of DNA can be emphasised
at this point: it is 3.4 nm in length for every ten bases and one complete turn of the helix.
There is no requirement for students to learn this detail.
Activity 2.14 Nucleic acids and protein synthesis (A2.14L)
This web-based tutorial and its accompanying worksheet take the student through the
process of protein synthesis. DNA and RNA structure and complementary base pairing in
both DNA and transcription are clearly demonstrated. The genetic code and translation are
illustrated.
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SNAB T2 Teaching scheme
(Note that the use of the sense and antisense in the student book follows common usage in
academic and industrial literature. Many A-level textbooks use these terms wrongly.)
2.5 What goes wrong with DNA?
DNA replication, how mutations can change the amino acids coded for, and the
consequences for the functionality of the protein produced, are illustrated using CF and
sickle cell anaemia.
This section starts with a description of DNA semi-conservative replication. Then it explains
how Meselson and Stahl’s classic experiment provided new data that supported the
accepted theory of replication of DNA and refuted competing theories.
Activity 2.15 Meselson and Stahl’s experiment on DNA replication (A2.15L)
This is a challenging activity. The interactive tutorial takes students through the Meselson
and Stahl experiments and the different theories of replication. Students interpret the results
and draw conclusions for themselves about which theory the evidence supports.
Teachers/lecturers need to check the activity to ensure that this approach is suitable for
their students, and if necessary support them as they complete the activity.
The Public Health Genetics Foundation website has a good educational resources section.
It includes information on a range of genetic diseases, epidemiology, ethical issues, and
genetic testing. The Wellcome Trust Sanger Institute has good online educational
resources. See the general weblinks for Topic 2.
The National Centre for Biotechnology Information in the USA has a series of gene maps
showing the location of disease related genes. See the general weblinks for Topic 2.
2.6 How is CF inherited?
Monohybrid inheritance is covered in this section. Although the title of the section refers to
CF, students need to be able to answer questions on other instances of monohybrid
inheritance.
Activity 2.16 Reebops (A2.16L)
Construction of Reebops (marshmallow organisms) illustrates the principles of monohybrid
inheritance in a student-friendly way.
Activity 2.17 Inheritance problems (A2.17L)
Questions are based on the inheritance of genetic diseases and other characteristics
including those mentioned in the specification: garden pea height and seed morphology.
Co-dominance and sex linkage are included as extension questions; these are not
described in the student book.
The Channel 4 website includes an interactive activity which investigates the inheritance of
sickle cell anaemia within one family. It is a good activity, although for an able student who
grasps the idea, having to complete the sequence of questions for every family member
could be tiresome. See the general weblinks for Topic 2.
2.7 How is CF treated?
Current ways of treating CF are described in a Did you know? box; they are not required by
the specification. However, gene therapy as a possible future treatment is included in the
specification and is described in the student book.
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SNAB T2 Teaching scheme
Activity 2.18 Gene therapy – another side to the story (A2.18L)
In this activity students use the student book to review the techniques used in gene therapy.
The activity also considers some of the problems encountered in the trials of this treatment.
The BBSRC website has downloadable information and activity sheets about new
technologies, including gene therapy. There is an excellent MRC update on cystic fibrosis
on the School Science website under biology 16–18 resources. It includes information about
the symptoms, causes and use of gene therapy with questions on each section. Duncan
Geddes at the Royal Brompton Hospital describes the UK trials in which he is involved. See
the general weblinks for Topic 2, and the Activity 2.18 weblinks.
Students could also search the Internet for the latest progress in the development of gene
therapy. Students should be aware that gene therapy research is being used not only for CF
but for other conditions too.
2.8 Testing for CF
Detailed descriptions in the student book and suggested activities cover testing for both CF
and for the presence of the CF mutation. Early diagnosis of CF, and consequent early
treatment, can have a significant beneficial effect on the health of the individual.
The student book describes the uses of genetic screening. Students need to be able to
explain the uses of genetic screening: identification of carriers, preimplantation genetic
diagnosis and prenatal testing (amniocentesis and chorionic villus sampling) and discuss
the implications of prenatal genetic screening. The BBSRC website has downloadable
information and activity sheets about CF, including a section on testing, it gives examples of
DNA samples that students can interpret. See the general weblinks for Topic 2.
It may be helpful if the continuing professional development module CPD4 Ethical debate is
completed by teachers/lecturers before undertaking Activity 2.19. The activity within the
CPD unit uses genetic screening to illustrate the use of the ethical frameworks and could be
used with students – see Ethical debate (D0.04F and D0.04L).
Students need to identify and discuss the social and ethical issues related to genetic
screening from a range of ethical viewpoints. The student book section ‘Making ethical
decisions – What is right and what is wrong?’ provides a set of ethical frameworks for
students to use when discussing and making decisions about ethical issues. Students
should study this before completing Activity 2.19 or engage in general class discussion
about these issues. The aim of Activity 2.19 is to encourage students to make a decision
about an ethical issue, and to support their decision using ideas based on the ethical
frameworks. The BioEthics Education Project (BEEP) website supports the teaching and
learning of bioethics. It includes a section on genes and health including CF.
Activity 2.19 Genetic screening (A2.19L)
Students read the newspaper article raising issues surrounding widespread carrier
screening, and then compose a reply either supporting or opposing the position taken by the
epidemiologist quoted in the article.
In Checkpoint question 2.7 students use the ethical frameworks to make decisions about
genetic screening.
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SNAB T2 Teaching scheme
The topic could finish with a class discussion about the options open to Claire and Nathan,
the couple in the opening story, and whether they should or should not have a child. It would
be interesting to recall any views expressed at the start of the topic and find out if the
students’ views have changed.
Activity 2.20 Passing it on (A2.20L)
This role-play provides a more structured format to discuss some of the issues covered in
the topic.
Activity 2.21 Gene mutation – a personal story (A2.21L)
This activity uses a real life story of a girl who has PKU to revise some of the ideas covered
in the topic.
Activity 2.23 Check your notes
Students can use the checklist of learning outcomes in this activity in their revision.
End-of-topic tests
There is an online interactive end-of-topic test. This test is not accessible to students initially
unless set by their teacher/lecturer. The teacher has the option to ‘flick a switch’ to make it
open access. There is also a paper-based test for Topic 2 with examination-style questions
on the teacher’s and technician’s sites. A mark scheme is also available on these sites. The
questions are similar in layout and style to those that are found on exam papers. However,
the restriction of questions to only one topic in each test has meant that it has not been
possible to include some types of questions that draw on material from different topics.
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13
SNAB T2 Teaching scheme
AS Summary chart
The grid below shows where concepts are introduced and then revisited in later topics.
Note: Some of these concepts will be revisited and built on in A2.
Concept
Biological
molecules
(monomers
combine to form
polymers)
Enzymes
Topic 1
 Carbohydrate structures and
roles in providing and storing
energy (not cellulose)
 Lipid structures
Chemical
reactions
 Condensation and hydrolysis
reactions
 Antioxidants and radicals
Topic 2
 Phospholipids
 Protein structures
 Structures of DNA and RNA
 Enzyme structure and
mechanism of action
 Effect of enzyme concentration
on rate of reaction
Cell structure
 Condensation reactions
 Hydrophobic and hydrophilic
effects
 Unit membrane structure
Topic 3
 Role of ER and Golgi apparatus in
formation of extracellular enzymes
 Condensation reactions









Genes help
determine the
nature of
organisms
Cell cycle
Roles of DNA and RNA
Genetic code
Protein synthesis
DNA replication and mutations




Energy
Transport in and
out of cells
 Energy units, energy balance
 Role of ATP in active transport
 Passive transport, diffusion,
facilitated diffusion, osmosis,
active transport, exocytosis and
endocytosis
Topic 4
 Starch and cellulose structures and
functions

Prokaryotic and typical eukaryotic
(animal) cell structure and
ultrastructure
Role of ER and Golgi apparatus
in protein transport
Gamete structures and functions
Stem cells
Cell specialisation and
organisation into tissues, organs
and organ systems
Cell specialisation through
differential gene expression
 Recall typical ultrastructure of animal cell
and compare with plant cell ultrastructure
 Xylem and sclerenchyma structure and
function
 Genetic diversity
DNA replication and cell and
nuclear division
Role of mitosis and cell cycle for
growth and asexual reproduction
Differentiation and the role of
stem cells
Protein transport
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 Diffusion and osmosis
14
SNAB T2 Teaching scheme
Concept
Transport in
organisms to
and from
exchange
surfaces
Organisms
exchange
materials with
the environment
Inheritance
Topic 1
 Mass transport
 Structure and function of the
circulatory system
 Solvent properties of water
 Genetic risk factors for CVD
 Interaction of genotype and the
environment on development of
CVD
 Monohybrid inheritance
Gene technology
 Gene therapy
 Gene therapy
 Genetic screening and embryo
testing
Topic 3
Topic 4
 Mass transport of waters and minerals
through plant stems
 Surface area to volume ratio
 Properties of gas exchange
surfaces
Evolution and
natural selection
Classification
Interactions with
the environment
Topic 2
 Effect of environment on CVD
risk
 Importance of meiosis and
fertilisation in sexual reproduction
 Role of meiosis in production of
genetic variation, including
independent assortment and
crossing over
 Some characteristics are affected by
genotype and the environment
 Polygenic inheritance
 Discontinuous and continuous
variation
 Genetic variation (loss and conservation)

Importance of meiosis and
fertilisation in sexual reproduction

Introduction of genetic variation
through random assortment (stages
of meiosis and chiasmata formation
are not required)

Some characteristics affected by
genotype and the environment
 Prokaryotes and eukaryotes


 Some characteristics are affected by
genotype and the environment






Energy flow and
recycling of
materials in
ecosystems
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Adaptation
Evolution by natural selection
 The concept of species
 Taxonomic groupings
Biodiversity
Endemism
Concept of Niche
Adaptations of organisms
Sustainable resource utilisation
Microbial properties of plants importance
of water and mineral ions to plants
 Sustainable resource utilisation
15
SNAB T2 Teaching scheme
Concept
Coordination
Topic 1
 Diabetes
Topic 2
 Endocrine and exocrine
hormones introduced
Topic 3
 Melanocyte stimulating hormone
(MSH)
Risk and
perception
 Concept of risk, risk perception,
risk factors for CVD, reducing
risk of CVD
 Genetic risk factors
 Risk factors for cancer
Maths/science
skills
 Calculating probabilities,
correlation and causation,
calculating obesity indicators,
analysis of quantitative health
data
 Calculating surface area to
volume ratios
 Continuous/discontinuous variation
Health and
Disease





CVD (CHD and stroke)
Cancer
Atherosclerosis
Blood clotting
Evaluate design of health
studies
 Experimental use of
invertebrates
 Cystic fibrosis, (briefly) sickle cell
and thalassaemia, PKU,
achondroplasia, Huntington’s
disease)
 Cancer
 Ethical frameworks
 Genetic screening
 Stem cells
 Sphygmomanometers / blood
pressure monitors
 Use of scientific knowledge to
reduce health risk
 Genetic testing / screening
 Gene therapy
 Use of stem cells for research
Ethics
Applications of
biology
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Topic 4
 The nature of theories, scientific
consensus and evidence
 Critical evaluation of new data
 Ecological sampling
 Measurement of biodiversity and genetic
diversity
 Drug development




Use of plant fibres
Use of plant starch and oils
Drug development
Role of zoos and seedbanks
16