A-level

BIOLOGY
7402/2
Paper 2
Mark scheme
June 2019
Version: 1.0 Final

*196A7402/2/MS*
 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant
questions, by a panel of subject teachers. This mark scheme includes any amendments made at the
standardisation events which all associates participate in and is the scheme which was used by them in
this examination. The standardisation process ensures that the mark scheme covers the students’
responses to questions and that every associate understands and applies it in the same correct way.
As preparation for standardisation each associate analyses a number of students’ scripts. Alternative
answers not already covered by the mark scheme are discussed and legislated for. If, after the
standardisation process, associates encounter unusual answers which have not been raised they are
required to refer these to the Lead Assessment Writer.

It must be stressed that a mark scheme is a working document, in many cases further developed and
expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark
schemes on the basis of one year’s document should be avoided; whilst the guiding principles of
assessment remain constant, details will change, depending on the content of a particular examination
paper.

Further copies of this mark scheme are available from aqa.org.uk

Copyright © 2019 AQA and its licensors. All rights reserved.

AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this
booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any
material that is acknowledged to a third party even for internal use within the centre.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Mark scheme instructions to examiners

1. General
The mark scheme for each question shows:
• the marks available for each part of the question
• the total marks available for the question
• the typical answer or answers which are expected
• extra information to help the examiner make his or her judgement and help to delineate what
is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area
in which a mark or marks may be awarded.

The extra information in the ‘Comments’ column is aligned to the appropriate answer in the left-
hand part of the mark scheme and should only be applied to that item in the mark scheme.
At the beginning of a part of a question a reminder may be given, for example: where
consequential marking needs to be considered in a calculation; or the answer may be on the
diagram or at a different place on the script.
In general the right-hand side of the mark scheme is there to provide those extra details which
confuse the main part of the mark scheme yet may be helpful in ensuring that marking is
straightforward and consistent.

2. Emboldening
2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is
used, with the number of marks emboldened. Each of the following bullet points is a
potential mark.
2.2 A bold and is used to indicate that both parts of the answer are required to award the
mark.
2.3 Alternative answers acceptable for the same mark are indicated by the use of OR.
Different terms in the mark scheme are shown by a / ; eg allow smooth / free movement.

3. Marking points
3.1 Marking of lists
This applies to questions requiring a set number of responses, but for which students
have provided extra responses. The general principle to be followed in such a situation is
that ‘right + wrong = wrong’.
Each error / contradiction negates each correct response. So, if the number of errors /
contradictions equals or exceeds the number of marks available for the question, no
marks can be awarded.
However, responses considered to be neutral (often prefaced by ‘Ignore’ in the
‘Comments’ column of the mark scheme) are not penalised.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

3.2 Marking procedure for calculations

Full marks can be given for a correct numerical answer, without any working shown.
However, if the answer is incorrect, mark(s) can usually be gained by correct substitution /
working and this is shown in the ‘Comments’ column or by each stage of a longer
calculation.

3.3 Interpretation of ‘it’

Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the
correct subject.

3.4 Errors carried forward, consequential marking and arithmetic errors

Allowances for errors carried forward are most likely to be restricted to calculation
questions and should be shown by the abbreviation ECF or consequential in the mark
scheme.
An arithmetic error should be penalised for one mark only unless otherwise amplified in
the mark scheme. Arithmetic errors may arise from a slip in a calculation or from an
incorrect transfer of a numerical value from data given in a question.

3.5 Phonetic spelling

The phonetic spelling of correct scientific terminology should be credited unless there is a
possible confusion with another technical term.

3.6 Brackets
(…..) are used to indicate information which is not essential for the mark to be awarded
but is included to help the examiner identify the sense of the answer required.

3.7 Ignore / Insufficient / Do not allow

Ignore or insufficient is used when the information given is irrelevant to the question or not
enough to gain the marking point. Any further correct amplification could gain the marking
point.
Do not allow means that this is a wrong answer which, even if the correct answer is
given, will still mean that the mark is not awarded.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

1. (Colonisation by) pioneer species; 4 max 2. Accept example of

change e.g. forms
2. Pioneers/species/organisms change the
soil/humus/organic
environment/habitat/conditions/factors;
matter/nutrients.
3. (Environment becomes) less hostile for
other/new species 2. Must convey idea of
OR change being caused by
pioneers/species/organisms
01.1 (Environment becomes) more suitable for
other/new species 3. Accept previous species
OR out-competed.

(Environment becomes) less suitable for 4.Ignore increase in genetic

previous species; diversity.
4. Change/increase in diversity/biodiversity;
5. (To) climax community;

1 Accept standard form e.g.

01.2 0.155; -2
15.5 x 10

1. Answer of 180/178/177.5 = 2 marks;;

2. Incorrect answer but shows use of numbers 2
1. Ignore any numbers
01.3 57 and 127 (with decimal points in any
position) within the calculation = 1 mark; following 177.5

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

3 1. Reject amino acids

are formed.
1. Change in (sequence of) amino acid(s)/primary
structure; 1. Reject amino acids
code.
02.1
2. Change in hydrogen/ionic/disulfide bonds;
3. Reject active site.
0
3. Alters tertiary/3 structure; 3. Ignore quaternary.
3. Ignore 3D.

1. Produce healthy (red blood) cells 3 1. Produce only

healthy (red blood)
OR
cells is only equivalent
Produce (normal) polypeptide/haemoglobin; to mark point 1.
2. No sickle/faulty/SCD (red blood) cells (produced) 1. Accept produce
OR ‘normal’/non-SCD
02.2 cells.
No defective polypeptide/haemoglobin;
1. and 3. Ignore type
3. Stem/marrow cells (continuously) divide/replicate of stem cell e.g.
OR pluripotent.

Less chance of rejection (from brother/sister); 3. Differentiate is not

equivalent to
divide/replicate.

(For gene therapy) 3 max Max 2 marks for

1. No destruction of bone marrow marking points 1, 2
and 3
OR 1. Accept no
destruction of faulty
No destruction of stem cells; bone marrow unless
context indicates this
2. Donors are not required; is against gene
therapy.
3. Less/no chance of rejection (own stem cells);
2. Stating ‘only own
(Against gene therapy) cells used’ is not
02.3
4. Sickle/faulty (red blood) cells still produced equivalent.
5. Accept ‘virus could
5. Immune response against genetically modified cause problems’ or
cells/virus ‘risk(s) with virus’.
OR

Long-term effect not known (as is new treatment)

OR

Virus could cause side effects;

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

2 max Mark in pairs 1 and 2

or 3 and 4.
1. Tip produces IAA; 1 and 2. Accept auxin
2. Affects concentration of IAA for IAA.

OR 1. Ignore
contains/stores IAA.
03.1 Affects (shoot) length/growth/elongation;
1. Accept affects
amount of IAA.
3. Mitosis/division occurs in shoot tips; 2. Accept affects
4. Affects (shoot) length/growth/elongation; independent variable.
2 and 4. Ignore
affects results.

2 1.Ignore
photosynthesis.
1. Ignore
aerobic/anaerobic
(respiration).
1. For respiration;
1. Reject glucose
03.2 2. Provide ATP/energy (for growth); used in
photosynthesis.
2. Reject produce
energy.
2. Do not credit
photosynthesis
provides ATP.

2 1. Accept evaporation
1. To prevent/reduce evaporation; of (IAA/glucose)
2. (Which) alters concentration of (IAA) solution ‘solution’.
03.3 2. Accept auxin for
OR IAA.
(Which) alters water potential; 1. Ignore
contamination.

3 1, 2 and 3. Accept
1. Increase in IAA concentration the higher/greater auxin for IAA.
the mean (change in) length;
3. Accept decrease in
03.4 2. (High) IAA stimulates cell elongation; (mean) change in
length but reject
3. In roots, growth/elongation less/inhibited;
‘decreases length’ on
its own.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

3. Accept ‘opposite
results or ‘negative
correlation’.

1 Both numbers
03.5 0.4 and 39.6; required and must be
in order shown.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

1. Lower (force of contraction) in mouse/B (than 4 max 1. Accept any

control/100%) below 29 °C temperature below 29
°C for mouse/B or any
OR
specified temperature
Lower (force of contraction) in rabbit/D (than below 26.5 °C for
control/100%) below 26.5 °C; rabbit/D.
2. Higher (force of contraction) in mouse/B (than 2. Accept any
control/100%) above 29 °C temperature above 29
°C for mouse/B or any
OR temperature above
Higher (force of contraction) in rabbit/D (than 26.5 °C for rabbit/D.
control/100%) above 26.5 °C; 1. and 2. Accept 27
3. Only (used) mouse and rabbit °C for 26.5 °C and
04.1 accept 28.5 °C for 29
OR °C.
3. Accept only two
No other organism/species used; animals/species used.
4. Body temperature of mouse/rabbit higher (than 4. Accept body
temperatures investigated); temperature of
5. Only used one/0.5 pH (below typical pH) mouse/rabbit not
known
OR
7. Ignore SD.
(Should) use more pH values;
6. (Used) isolated muscle tissue;
7. No stats test to see if (difference is) significant;

1. (Less/No) tropomyosin moved from binding site 3 1 and 2. Reject active

site only once.
OR
1. Ignore troponin.
Shape of tropomyosin not changed so binding
site not exposed/available; 2. Accept actin and
myosin do not bind.
2. (Fewer/No) actinomyosin bridges formed;
3. Reject ATP
3. Myosin head does not move
synthase.
OR
Do not penalise
04.2 Myosin does not pull actin (filaments) reference to calcium
rather than calcium
OR
ions.
(Less/No) ATP (hydrol)ase (activation);
Credit all mark points
even if context relates
to what happens
when calcium ions are
present.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

1. Regenerates/produces NAD 2 1. Reject NADP and

any reference to FAD.
OR
1. Accept descriptions
oxidises reduced NAD;
of oxidation e.g. loss
2. (So) glycolysis continues; of hydrogen.

04.3 2. Accept description

of glycolysis e.g.
glucose to pyruvate.
2. Accept ‘for
oxidising/converting
triose phosphate to
pyruvate’.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

1. (Attaches to receptors on target cells and) 2 1. Reject ‘produces

activates/stimulates enzymes; enzymes’.
2. Glycerol/amino acids/fatty acids into glucose; 2. Reject ‘glucagon
converts’ as context
suggests enzyme
05.1 action.
2. Ignore
lipids/fats/proteins but
reject glycogen.
2. Reject occurs in
pancreas.

1. Correct answer of 3.24 = 2 marks;; 2

2. Incorrect but multiplies by 34 (with decimal point
in any position) = 1 mark
05.2 OR
Incorrect but shows sequence 324 = 1 mark
OR
3.2 = 1 mark;

1. (More) insulin binds to receptors; 2 2. Accept activates

enzymes for
2. (Stimulates) uptake of glucose by
glycogenesis.
channel/transport proteins
2. Reject active
OR
transport.
Activates enzymes which convert glucose to
2. Accept carrier
glycogen;
05.3 proteins or GLUT 4
for channel proteins.
2. Accept insulin
stimulates addition of
channel proteins in
membranes.

1. Less/no ATP is converted to cyclic AMP/cAMP; 3 If no indication of

2. Less/no kinase is activated; less/no for any of the
mark points award
3. Less/no glycogen is converted to glucose max 2 marks.
05.4 OR Accept all marks in
Less/no glycogenolysis; context of adrenaline.
Ignore
gluconeogenesis.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

06.1 1. Accept alleles in

any order.
GgXRXr ; 1
1. Accept GgRr with
alleles in any order.

06.2 If it were recessive all flies of 3 and 4 would be grey

OR
3 and 4 produce 9/black (fly) 1
OR
Grey parents produce black (fly);

06.3 1. (Fly) 3 (and 4) produce 9/black (fly) Mark in pairs 1 and 2

or 3 and 4.
OR
2. Accept allele for
(Fly) 9 would not be black
grey colour would be
OR passed on by 3.
(Fly) 9 would be grey
OR
Grey parents/male produce black female (fly);
2. (Fly) 3 would pass dominant allele to 9;
2 max
3. (Fly) 2 (and 1) produce 5/grey (fly)

OR
Black female produces grey male 4. Accept allele for
black colour would be
OR
passed on by 2.
(Fly) 5 could not be grey
OR
(Fly) 5 would be black;
4.(Fly) 5 would receive recessive allele from 2;

06.4 1. GgXrXr and ggXRY; 1 and 2. Accept the

R r R r r r following alternative
2. GgX X , ggX X , GgX Y and ggX Y;
notations for sex-
3. Grey-bodied red-eyed female, black-bodied linked crosses e.g. for
red-eyed female, grey-bodied white-eyed mp 1
3
male, black-bodied white-eyed male and ratio Ggrr and ggRY or

1 : 1 : 1 : 1; Ggrr and gg R- or
Ggrr and ggR
i.e. space for Y

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

If 1, 2 and 3 incorrect allow one mark for correct chromosome.

gametes from incorrect dihybrid parental
genotypes.
2 and 3. Accept any
order of genotypes
and phenotypes.
3. Accept sequence of
phenotypes does not
need to mirror
genotypes but must
be correct.
3. Accept alternative
ratios in correct
proportions e.g.
4:4:4:4

06.5 1. Correct answer of 48% = 2 marks;; 1. Accept 0.48 for 1

mark.
2. Incorrect answer but shows understanding that
2. Accept
2pq = heterozygous/carriers = 1 mark
2 understanding of 2pq
OR by using a calculation
Incorrect answer but shows understanding that involving 2 x two
different numbers.
2 2
1 – (p + q ) = heterozygous/carriers = 1 mark;

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

07.1  NADP, ADP, Pi and water; 1

07.2 1. Chlorophyll absorbs light 2 1. Ignore

photosystems.
OR
2. Ignore
Light excites/moves electrons in chlorophyll;
site/molecule from
where electrons are
2. Electron/s are lost lost.

OR 2. Accept electrons go
to electron
(Chlorophyll) becomes positively charged; transport/carrier chain
for ‘electrons lost’.

07.3 1
Ink and (leaf) pigments would mix
OR
(With ink) origin/line in different position
OR
(With pencil) origin/line in same position
OR
(With pencil) origin/line still visible;

07.4 1. Level of solvent below origin/line; 2 1. Reject water or any

2. Remove/stop before (solvent) reaches top/end; named aqueous
solution.
1. Accept named
organic solvent.

07.5 Accept any answer in range of 0.58 to 0.62; 1 Accept 0.58 or 0.62.
Ignore any numbers
which follow numbers
in range.

07.6 (Absorb) different/more wavelengths (of light) for 1 Accept wider/larger

photosynthesis; range of wavelengths.
Accept frequency for
wavelength.
Accept light-
dependent reaction
/photophosphorylation
/photoionisation for
photosynthesis.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

08.1 1. (Short) single strand of DNA; 2

2. Bases complementary (with DNA/allele/gene);

08.2 1. Restriction endonuclease/enzyme; 2 2. Accept palindromic

2. (Cuts DNA at specific) base sequence sequence.

OR
(Breaks) phosphodiester bonds
OR
(Cuts DNA) at recognition/restriction site;

08.3 (So DNA) probe binds/attaches/anneals; 1

08.4 1. (Lane 1 has DNA fragments) of known 2

sizes/lengths;
2. Compare (position of viral fragment/s);

08.5 1 All three numbers

3, 4, 5 with these numbers in any sequence;
required.
Reject if more than
three numbers given.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

Question Marking Guidance Mark Comments

09.1 1. Use a grid 5 1. Accept use of tape

measures/map/area
OR
with coordinates.
Divide area into squares/sections;
1. Accept Belt
transect.
2. Method of obtaining random
coordinates/numbers e.g. 2. If transect method
calculator/computer/random numbers used accept quadrats
table/generator; at regular intervals or
current mark point 2.
3. Count number/frequency in a quadrat/section;
3. Accept % cover in
quadrat/section.
4. Large sample and calculate mean/average
number (per quadrat/section); 3. Ignore
amount/abundance.
5. Valid method of calculating total number of 4. Accept large
sundews, e.g. mean number of plants per sample and calculate
quadrat/section/m2 multiplied by number of mean %.
quadrats/sections/m2 in marsh;
4. Accept large
sample and method
of calculating mean.

4. Accept
many/multiple for
large sample but
ignore several.

4.If a specific number

is given it must be 10
or more.

5. Do not allow ‘scale

up’ without further
qualification.

5. Do not award if %
cover determined.

09.2 1. Digestion/breakdown of proteins; 2 max Mark in pairs 1 and

2, or 3 and 4.
2. Provides amino acids
OR Ignore carbohydrates,
(Sundew can) produce a named (organic) lipids or named
nitrogen-containing compound e.g. proteins, carbohydrate/ lipid.
amino acids, DNA, ATP; 2. Ignore if nitrate or
3. Digestion/breakdown of named (organic) ammonium ions given
phosphate-containing compound e.g. DNA, RNA; as products.
4. Provides named (organic) phosphate-containing 4. Accept phosphate
product e.g. nucleotides as a named product.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

OR
(Sundew can) produce a named phosphate-
containing compound e.g. ATP, DNA;

Question Marking Guidance Mark Comments

10.1 1. (Refers to) saltatory conduction 3 1. Accept suitable description

that refers to (transmission)
OR
from node to node (of
(Nerve) Ranvier).
impulses/depolarisation/ions pass 1 and 2. Accept action
to other neurones potentials for impulses.
OR 1. Accept action potential for
Depolarisation occurs along whole depolarisation.
length (of axon); 1, 2 and 3. Reject first mark
2. (Nerve) impulses slowed/stopped; awarded if answer refers to
messages/signals for
3. (Refers to) neuromuscular junction impulses. Reject even if
OR impulse/s also referred to.
(Refers to) sarcolemma;

10.2 1. Slower/fewer impulse(s) along 3 1. Accept action potentials

sympathetic/parasympathetic for impulses.
(pathway/neurones);
1.Reject no impulses.
1, 2 and 3. Ignore
2. (Impulses) from cardiac centre ‘information’ but reject first
mark awarded if answer
OR
refers to messages/signals
(Impulses) from medulla; for impulses. Reject even if
impulse/s also referred to.
3. To SAN;

10.3 1. It/DNA is complementary to 3 1. Accept (transcription)

(m)RNA; results in complementary
(m)RNA.
2. Binds to mRNA (for huntingtin);
3. Prevents translation; Ignore
miRNA/siRNA/transcriptional
factors.

3. Ignore transcription.

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

2 max
10.4 1. Small sample size 3. Accept huntington for
OR huntingtin.

Only 46; Ignore

miRNA/siRNA/transcriptional
2. Only four-months factors.
OR
short period (of trial);
3. Huntingtin/protein reduced
OR
Huntingtin/protein still produced
OR
Huntingtin/protein not removed;
4. Allele/gene/mutation/mRNA (for
Huntington’s) still present

OR

(May be) temporary

OR

Drug treatment repeated;

5. Brain already damaged

OR

Brain damage may continue;

10.5 1. (Drug/DNA) will directly/quickly 2 2. Reject protein is digested.

reach brain
2. Ignore location of
OR enzymes.
(Cerebrospinal) fluid bathes the 2. Accept Drug/DNA
brain; denatured.
2. (Drug/DNA) not destroyed by acid

OR

(Drug/DNA) not digested (by

enzymes);

10.6 2 max Mark in pairs but if no mark

1. (Increased) methylation of
credited allow one mark for
DNA/gene/allele;
any reference to transcription
2. Inhibits/prevents transcription; or gene expression being
affected.
OR

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 MARK SCHEME – A LEVEL BIOLOGY – 7402/2 – JUNE 2019

1. Reject acetylation of DNA.

3. Decreased methylation of
Accept gene expression for
DNA/gene/allele;
transcription but ignore gene
4. Stimulates/allows transcription; switched on/off.
Ignore methylation of
OR histones.

5. Decreased acetylation of Accept DNA-histone complex

histone(s); as equivalent to histone(s).

6. Inhibits transcription; .

OR
7. Increased acetylation of histone(s);
8. Stimulates/allows transcription;

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