AQA A Level Biology Paper 3 2021 Marking Scheme

Question Marking Guidance Mark Comments

01.1

1. Answer of 12/13 = 2 marks;;

2. 0.36(48)/0.365/0.37 = 1 mark

OR

36(.48)/36.5/37% = 1 mark

OR

q

2

= 0.06/0.059/0.0588 = 1 mark

OR

or q = 0.2/0.24/0.243 = 1 mark;

2 For 1 mark accept q2

= 6%/5.9%/5.88%

Question Marking Guidance Mark Comments

01.2 0.71 1

Question Marking Guidance Mark Comments

01.3

Second box ticked/answer key: B:

The mutation that caused black fur happened in a

common ancestor of S. carolinensis and other

closely related species.

1

Question Marking Guidance Mark Comments

01.4

1. 2.55% = 2 marks;;

2. 2.61% = 1 mark (question misread ie

8/306x100)

OR

Evidence of dividing by 314 or 942 = 1 mark

OR

Answers not given to three significant figures = 1

mark;

2

MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2021

6

Question Marking Guidance Mark Comments

01.5

1. Mutation/lack of glutamic acid leads to

(permanent) activation of the receptor/protein;

2. (Because) the receptor/protein does not require

the binding/leaving of αMSH (to become activated);

3. ASIP (might) not (be) able to bind to the

receptor/protein;

4. (Only) the dark pigment is produced

3 max

2. Answer must

convey the idea that

binding/leaving is not

required

MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2021

7

Question Marking Guidance Mark Comments

02.1

1. RNA converted into DNA using reverse

transcriptase;

2. DNA incorporated/inserted into (helper T

cell) DNA/chromosome/genome/nucleus;

3. DNA transcribed into (HIV m)RNA;

4. (HIV mRNA) translated into (new) HIV/viral

proteins (for assembly into viral particles);

4

1. Reject ‘messenger’ or

‘m’ before RNA

3. Accept descriptions of

transcription

4. Accept descriptions of

translation

4. Accept named viral

protein, eg capsid

4. Reject viral cells