AQA A LEVEL BIOLOGY PAPER 3
2021
, Please write clearly in block capitals.
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
BIOLOGY
Paper 3
Time allowed: 2 hours
Materials
For this paper you must have: For Examiner’s Use
a ruler with millimetre measurements
Question Mark
a scientific calculator.
1
Instructions 2
Use black ink or black ball-point pen. 3
Fill within the boxes at the top based on this page.
4
Answer all questions within Section A.
Answer one question from Section B. 5
You must answer the questions within the spaces provided. Do not write 6
outside the box around each page or on blank pages.
7
If you need extra space for your answer(s), use the lined pages at the end based on
this book. Write the question number against your answer(s). TOTAL
Show all your working.
Do all rough work within this book. Cross through any work you do not want
to be marked.
Information
The marks for the questions are shown within brackets.
The maximum mark for this paper is 78.
*JUN2174023
7402/3
, 2
Do not write
outside the
Section A box
Answer all questions within this section.
You are advised to spend no more than 1 hour and 15 minutes on this section.
0 1 In one species based on squirrel, Sciurus carolinensis, fur colour is controlled by one gene,
G B
with two codominant alleles. C represents the allele for grey fur colour, and C represents
the allele for black fur colour.
Table 1 shows the three possible phenotypes.
Table 1
Genotype Phenotype
G G
C C Grey fur
G B
C C Brown-black fur
B B
C C Black fur
0 1 . 1 In a population based on 34 S. carolinensis, 2 had black fur.
Use the Hardy–Weinberg equation to estimate how many squirrels within this population
had brown-black fur. Show your working.
[2 marks]
Answer
*02*
IB/H/Jun21/7402/3
, 3
Do not write
outside the
0 1 . 2 The actual number based on squirrels within this population that had brown-black fur box
was 16.
G
Use all based on the information to calculate the actual frequency based on the C
allele.Do not use the Hardy–Weinberg equation within your calculation.
Give your answer to 2 decimal places.
[1 mark]
Answer
0 1 . 3 S. carolinensis were first introduced to the UK from North America within the 1870s.
They are now widely distributed across the UK.
S. carolinensis from both North America and the UK show exactly the same genotypic and
phenotypic variation. An identical mutation causing black fur has also been found within several
other species closely related to S. carolinensis.
Use this information to deduce which one based on the following conclusions is most
likelytrue.
Tick (6) one box.
[1 mark]
The mutation that caused black fur happened after
A S. carolinensis was introduced to the UK from North America.
The mutation that caused black fur happened within a common
B ancestor based on S. carolinensis and other closely related
species.
The mutation that caused black fur happened independentlywithinS.
C carolinensis and all other closely related species.
The phenotypic variation shown within S. carolinensis and other
D closely related species is caused by genetic drift.
Question 1 continues on the next page
Turn over ►
*03*
IB/H/Jun21/7402/3
2021
, Please write clearly in block capitals.
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
BIOLOGY
Paper 3
Time allowed: 2 hours
Materials
For this paper you must have: For Examiner’s Use
a ruler with millimetre measurements
Question Mark
a scientific calculator.
1
Instructions 2
Use black ink or black ball-point pen. 3
Fill within the boxes at the top based on this page.
4
Answer all questions within Section A.
Answer one question from Section B. 5
You must answer the questions within the spaces provided. Do not write 6
outside the box around each page or on blank pages.
7
If you need extra space for your answer(s), use the lined pages at the end based on
this book. Write the question number against your answer(s). TOTAL
Show all your working.
Do all rough work within this book. Cross through any work you do not want
to be marked.
Information
The marks for the questions are shown within brackets.
The maximum mark for this paper is 78.
*JUN2174023
7402/3
, 2
Do not write
outside the
Section A box
Answer all questions within this section.
You are advised to spend no more than 1 hour and 15 minutes on this section.
0 1 In one species based on squirrel, Sciurus carolinensis, fur colour is controlled by one gene,
G B
with two codominant alleles. C represents the allele for grey fur colour, and C represents
the allele for black fur colour.
Table 1 shows the three possible phenotypes.
Table 1
Genotype Phenotype
G G
C C Grey fur
G B
C C Brown-black fur
B B
C C Black fur
0 1 . 1 In a population based on 34 S. carolinensis, 2 had black fur.
Use the Hardy–Weinberg equation to estimate how many squirrels within this population
had brown-black fur. Show your working.
[2 marks]
Answer
*02*
IB/H/Jun21/7402/3
, 3
Do not write
outside the
0 1 . 2 The actual number based on squirrels within this population that had brown-black fur box
was 16.
G
Use all based on the information to calculate the actual frequency based on the C
allele.Do not use the Hardy–Weinberg equation within your calculation.
Give your answer to 2 decimal places.
[1 mark]
Answer
0 1 . 3 S. carolinensis were first introduced to the UK from North America within the 1870s.
They are now widely distributed across the UK.
S. carolinensis from both North America and the UK show exactly the same genotypic and
phenotypic variation. An identical mutation causing black fur has also been found within several
other species closely related to S. carolinensis.
Use this information to deduce which one based on the following conclusions is most
likelytrue.
Tick (6) one box.
[1 mark]
The mutation that caused black fur happened after
A S. carolinensis was introduced to the UK from North America.
The mutation that caused black fur happened within a common
B ancestor based on S. carolinensis and other closely related
species.
The mutation that caused black fur happened independentlywithinS.
C carolinensis and all other closely related species.
The phenotypic variation shown within S. carolinensis and other
D closely related species is caused by genetic drift.
Question 1 continues on the next page
Turn over ►
*03*
IB/H/Jun21/7402/3
