In this bundle there are more than 5000 aqa a level biology questions and if you do every question and memorise the mark scheme you will get that A* without a doubt
1. (a) Multiple alleles only involve one gene/one locus/polygene more than one gene: 1
A A A O
(b) (i) T T and T T ; 1
B C
(ii) T and T ; 1
(c) (i) Phenotypes of parents (Inhibitors) A and B (Inhibitor) B;
A B B O
Genotypes of parents T T T T ;
A B A O B O B B
Genotypes of offspring T T T T T T T T : 3
(ii) Assess probability;
of results being due to chance; 2
or Significant difference;
Between O & E/from Null hypothesis;
(d) Random sampling/known area;
Weighing all plant material (finding dry mass of plants); 2
(e) (i) Percentage in each case is 9 – 10, 7.5 – 12.5;
Energy in each case is 36 – 40kJ 3 – 5kJ; 2
or 0.36 0.4% 0.027 0.05%
36 40kJ 2.5 5kJ
(ii) Any two from
Lost as heat; in respiration; movement; excreted material:
egested/not all digested:
not all eaten; 2
[14]
2. (a) (i) Lepus; 1
(ii) Lagomorpha; 1
(b) (i) Distribution / habitat overlaps / found in the same place; 1
(ii) Geographical isolation / separation / barrier;
Adapted to slightly different conditions / environment /
different selection pressure;
Mutation in one population / different mutations; max 2
[5]
Sir George Monoux Sixth Form College 1
, B b
3. (a) (i) X X /XBXb 1
(ii) Need two X chromosomes / males have only one X /
male has a Y / X and Y chromosome / no allele on Y; 1
b b B
(b) Parental genotypes XX X Y
b B
gamete genotypes X X Y;
b B b
offspring genotypes XX X Y / correct from
given gametes
if sex-linked;
percentage of tortoiseshell kittens = 50% / correct from offspring genotype
given; 3
[5]
4. (a) (i) Substitutions;
only affect specific codons/not all codons affected;
therefore only a few amino acids affected;
or
Degenerate code;
some amino acids have more than one codon;
may mean mutations code for same amino acids/
only a few amino acids affected; max 2
(ii) Frame shift/sequence of bases/codons/triplets changed from that
point on;
sequence of amino acids changed;
protein will have different tertiary structure;
active site affected; max 3
(b) Genetic probe is single stranded DNA;
with complementary base sequence/is a complementary strand;
chains of DNA separated (by heating);
probe attached by hydrogen bonding;
probe labelled/radioactive/fluorescent so can be detected;
(If probe described as RNA, then max =2) max 3
A O
(c) (i) I and I ; 1
(ii) Blood group B; 1
(iii) Probability of child being boy indicated as 0.5 and probability
of child being blood group A indicated as 0.5;
0.25 or other correct expression; 2
(d) (i) Person with blood group O has no antigens/has unchanged antigens;
cannot provoke a response by antibodies/cannot cause a
reaction/agglutination/with anti A or anti B;
(Not just ‘immune response’) 2
(ii) Person with blood group O has both anti A and anti B/
has both antibodies;
will react with/agglutinate any red cells with any antigens/
A/B / AB / have antigens which will react;
(do not allow ‘attack’) 2
Sir George Monoux Sixth Form College 2
, (e) (i) 0.27; 1
(ii) Blood groups B and O have anti-A antibodies;
these match/fit A antigen;
which has similar shape to surface proteins on smallpox virus;
recognition as non-self
may also agglutinate/react with/fit/match smallpox antigen; max 3
[20]
5. (a) Genus; 1
(b) (i) Prefer / more likely to mate with male of same species; 1
(ii) Appropriate / species-specific courtship by male /
courtship not recognised;
chemical attraction / pheromones;
compatible genitalia; max 2
(iii) (Geographical) isolation;
mutations / genetic differences;
selection;
(isolation lead to) reproductive isolation /
populations no longer able to mate; 3
[7]
6. (a) (All) the alleles/genes in a population/ definition; 1
(b) Two. All somatic/ body cells are diploid/have two copies of each
chromosome/ must be homozygous for phenotype to be expressed; 1
(c) (i) 2 marks 0.%
1 mark incorrect figure obtained from 0.16 2
(ii) 60% / 0.6 but accept answer derived correctly from (c)(i); 1
[5]
7. (a) Insecticide resistance already in population;
(resulting) from mutation;
resistant insects are not killed (by insecticide)/survive;
(And are able to) reproduce/breed;
passing on the relevant allele/gene to the next generation/offspring;
resulting in increasing frequency of resistance allele in population. max. 5
(b) (i) Surviving/resistant moths are homozygous recessive/rr;
moths from untreated fields/non-resistant will be RR/Rr;
crossing these produces heterozygotes/Rr;
non resistant are susceptible and die;
Allow annotated diagrams
(ii) (If the allele were dominant) all heterozygotes would survive
(and be able to breed);
pass on dominant allele/gene;
increasing frequency/number/of resistant individuals/moths; max. 6
[11]
Sir George Monoux Sixth Form College 3
, 2
8. (a) EITHER: q = 0.36 / q = 0.6/0.61;
p = (1 – 0.6) = 0.4/0.39;
48/47.9 = 3 marks
OR (If no correct calculations)
Allow 1 mark for use of H – W equation:
2+ 2
p + q = 1 /p 2pq + q = 1 max. 3
(b) No selection;
random mating/no sexual selection;
large population/gene pool;
no emigration/immigration/no migration/isolated population;
no mutation;
equally viable gametes/all equally fertile;
generations do not overlap; max. 2
[5]
– –
9. (a) (i) Nitrate/NO 3 /nitrite/ NO 2 ; 1
(ii) Nitrification; 1
(iii) Denitrification; 1
–1
(b) (i) (Increase) fertiliser increases yield up to 150 kg hectare ; 1
(ii) (Excess) runs off/leaching/washed out;
eutrophication;
no extra yield;
cost (only once)/economic waste;
kills crops; due to osmotic effects/pH imbalance; max. 4
(c) (i) Continuous; 1
(ii) A has a smaller range of heights;
A is shorter/explained;
A is skewed;
(allow converse) max. 2
(iii) Mutation;
selection;
genetic modification; max. 2
(iv) Less stem damage in wind;
more energy used for seed formation/greater yield of seed/grain;
easier to harvest; max. 2
(d) (i) AB and ab; spaced or ringed 1
(ii) Genotype: AaBb;
Phenotype: 70cm 2
[18]
10. (a) 1ndividual 7 Ff, 1
individual 11 FF and Ff, 1
1
(b) Working shows probability next child will have cystic fibrosis = 4 or 0.25
and M/F = 50% / 0.5/½;
1
answer given as . (chance) in .5%; 2
Sir George Monoux Sixth Form College 4
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