Download AQA Biology Question number Answer Marks Guidance 1 a i (In all

20 Gene expression
Exam-style mark scheme
AQA Biology
Question
number
Answer
Marks
1ai
(In all organisms/DNA,) the same triplet codes
for the same amino acid
1
1 a ii
64
1
1b
Splicing
1
1ci
Any three from:
1 (Mutation) changes triplets/codons after that
point/causes frame shift
2 Changes amino acid sequence (after
this)/codes for different amino acids (after
this)
3 Affects hydrogen/ionic/sulfur bond (not
peptide bond)
4 Changes tertiary structure of protein (so
non-functional)
1 c ii
1
2
Intron non-coding (DNA)/only exons coding
(So) not translated/no change in mRNA
produced/no effect (on protein)/no effect on
amino acid sequence
Guidance
Accept codon/same three
bases/nucleotides
Accept plurals if both triplets and
amino acids
Reject triplets code for an amino
acid
Reject reference to producing
amino acid
Ignore deletion references
Accept RNA splicing
3 max
Accept changes splicing site
1 Ignore changes in sequence
of nucleotides/bases
2 Accept changes primary
structure
2 Reject changes amino acid
formed/one amino acid
changed
4 Neutral 3-D structure
2
Context is the intron
Do not mix and match from
alternatives
1 Neutral references to introns
removed during splicing
1 and 2 Ignore ref. to code
degenerate and get
same/different amino acid in
sequence
2 Accept does not code for
amino acids
4 Accept exons not joined
together/introns not removed
OR
Any two from:
3 Prevents/changes splicing
4 (So) faulty mRNA formed
5 Get different amino acid sequence
8
2a
Any two from:
1 Change in inherited gene function
2 Without change in genotype/gene/base
sequence (of DNA)
3 Caused by environmental factor
2bi
24 / 24.2
2 max
2
70
1.7 2
Reject reference to mutations
Ignore references to
maternal/paternal
Correct answer (24 or 24.2) gains
2 marks; working out (70 1.72)
but answer incorrect gains 1 mark
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1
20 Gene expression
Exam-style mark scheme
AQA Biology
Question
number
Answer
2 b ii
1
2
2c
Any three from:
1 Larger/higher concentrations are in boys
with syndrome
2 But overlap with boys without syndrome
3 The highest ghrelin concentration/about 680
is in boy who is not obese/has BMI of
about 25
4 A boy with the syndrome who has the
lowest ghrelin concentration/ghrelin
concentration of about 150 but is obese/has
a BMI of about 48
5 No/weak correlation (for boys with the
syndrome)
6 Only a few results, so conclusion may not
be reliable
7 Other factors not considered (that lead to
obesity)
8 Can’t be sure because no statistical analysis
Negative correlation
(And) the more overweight a boy is, the less
ghrelin he has in his blood
Marks
Guidance
2
3 max
Reject references to not knowing
the sample size
9
3ai
Mass of cells dividing/growing out of control
1
3 a ii
When cells from tumour have spread to other
parts of body/metastasis has happened
1
3b
1
2
2
3c
mdm/proteins have specific
shapes/structures
Only complementary shapes bind together
Any five from:
1 (New) tumour has few blood vessels, so
little oxygen
2 This should activate production of p53
protein
3 p53 protein stops growth/kill cancer
cells/repair cancer cells’ DNA
4 Cells in tumour produce (a lot of) HDAC in
low oxygen conditions
5 This prevents p53 being produced/p53 gene
being expressed/transcribed
6 Removal of acetyl groups (by HDAC)
prevents transcription (of p53 gene)
7 So not enough p53 protein/expression to
stop tumour growth
1
2
Accept complementary
Reject references to enzymes
or active sites
5 max
9
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This resource sheet may have been changed from the original
2
20 Gene expression
Exam-style mark scheme
AQA Biology
Question
number
4a
Answer
Any two from:
1 All the genes
2 On a (full/haploid) set of chromosomes/
genes in mitochondria or chloroplasts
Marks
Guidance
2 max
There are variants on these forms
of wording
OR
1 The base sequences
2 On a (full/haploid) set of chromosomes/all of
the DNA
4b
1
2
4c
Any two from:
1 S shaped curve
2 No/not much response up to (about) 1000
units/no further increase above 10 000 units
3 Sharp/steep change above (about) 1000
units
4 Negative correlation
2 max
4d
Any three from:
1 The protein causes antibody production (in
people)
2 Antibody transferred to mosquito when
(infected) human is bitten
3 Stops Plasmodium infecting mosquitoes
4 So malaria not transferred to another human
5 Over time, fewer and fewer mosquitoes
carrying malaria
3 max
Pfs is an antigen
Causes an immune response/antigen binds
to cell/B cell/ causes antibody production
2
9
5a
Correct answer: 1.8: 1 / 1.8 / 9 : 5
OR (if wrong answer)
2
27
/ 27 : 15 for 1 mark
15
5bi
1
2
5 b ii
Any three from:
1 Tamoxifen/endoxifen prevents oestrogen
binding to receptor/competes with oestrogen
for receptor
2 Endoxifen-receptor complex: cannot bind to
DNA/does not affect DNA
OR
2 No oestrogen-receptor complex to bind to
the DNA
Similar shape/structure to oestrogen
Complementary to/fits receptor
2
3 max
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This resource sheet may have been changed from the original
3
20 Gene expression
Exam-style mark scheme
AQA Biology
Question
number
Answer
Marks
Guidance
OR
2 Endoxifen-receptor complex binds to DNA
but cannot bind to co regulator
3 Does not activate a gene/does not activate
protein synthesis/transcription
OR
3 Does not activate proto-oncogene/does not
inhibit tumour-suppressor gene/does not
allow methylation of tumour-suppressor
gene
4 Inhibits cell division/does not stimulate cell
division
Accept example – enzyme/DNA
methyl transferase
7
© Oxford University Press 2016 http://www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original
4