AQA AS Biology Paper 1 2021 Marking Scheme

Question Marking Guidance Mark Comments

01.1 1. Hydrogen (bonds);

2. Phosphodiester (bonds);

2

2. Accept

ester/covalent bond

Question Marking Guidance Mark Comments

01.2 Correct answer for 2 marks = 1489/1489.2;;

Incorrect answer but for 1 mark accept:

876

OR

1861 - 1862

2

Question Marking Guidance Mark Comments

01.3

1. tRNA is 'clover leaf shape', mRNA is linear;

2. tRNA has hydrogen bonds, mRNA does not;

3. tRNA has an amino acid binding site, mRNA

does not;

4. tRNA has anticodon, mRNA has codon;

2

Must be a comparison

1. Reject tRNA is

double stranded

1. Accept tRNA is

folded for tRNA is

‘clover leaf shaped’

3. Accept ‘CCA end'

for amino acid binding

site

MARK SCHEME – AS BIOLOGY – 7401/1 – JUNE 2021

6

Question Marking Guidance Mark Comments

01.4 1. mRNA fewer nucleotides

OR

Pre-mRNA more nucleotides

OR

mRNA has no introns/has (only) exons

OR

Pre-mRNA has (exons and) introns;

2. (Because of) splicing;

2

1. Accept mRNA is

shorter OR pre-mRNA

is longer

TOTAL 8

MARK SCHEME – AS BIOLOGY – 7401/1 – JUNE 2021

7

Question Marking Guidance Mark Comments

02.1 1. A = Attachment protein;

2. B = Capsid

 OR

 Capsomere

 OR

 Protein;

2

1. Accept gp41

/gp140

/gp120/CD4/

glycoprotein

1. Accept antigen

1. Ignore receptor

protein

Question Marking Guidance Mark Comments

02.2 1. Attachment proteins attach to receptors on helper

T cell/lymphocyte;

2. Nucleic acid/RNA enters cell;

3. Reverse transcriptase converts RNA to DNA;

4. Viral protein/capsid/enzymes produced;

5. Virus (particles) assembled and released (from

cell);

4 max