AS BIOLOGY 7401/2 Paper 2 Mark scheme June 2022 Version: 1.0 Final *226A7401/2/MS*

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AS BIOLOGY 7401/2 Paper 2 Mark scheme June 2022 Version: 1.0 Final *226A7401/2/MS* MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 2 Mark schemes are prepared by the Lead Assessment Writ... er and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from aqa.org.uk Copyright information AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre. Copyright © 2022 AQA and its licensors. All rights reserved. MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 3 Mark scheme instructions to examiners 1. General The mark scheme for each question shows: • the marks available for each part of the question • the total marks available for the question • the typical answer or answers which are expected • extra information to help the examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. The extra information in the ‘Comments’ column is aligned to the appropriate answer in the lefthand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right-hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent. 2. Emboldening 2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is used, with the number of marks emboldened. Each of the following bullet points is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for the same mark are indicated by the use of OR. Different terms in the mark scheme are shown by a/; eg allow smooth/free movement. 3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’. Each error/contradiction negates each correct response. So, if the number of errors/contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (often prefaced by ‘Ignore’ in the ‘Comments’ column of the mark scheme) are not penalised. MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 4 3.2 Marking procedure for calculations Full marks can be given for a correct numerical answer, without any working shown. However, if the answer is incorrect, mark(s) can usually be gained by correct substitution/working and this is shown in the ‘Comments’ column or by each stage of a longer calculation. 3.3 Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. 3.4 Errors carried forward, consequential marking and arithmetic errors Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation ECF or consequential in the mark scheme. An arithmetic error should be penalised for one mark only unless otherwise amplified in the mark scheme. Arithmetic errors may arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question. 3.5 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term. 3.6 Brackets (…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 3.7 Ignore/Insufficient/Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 5 Question Marking Guidance Mark Comments 01.1 A sequence of DNA (nucleotide) bases that codes for a polypeptide; 1 (AO1) Ignore codes for a protein. Accept ‘codes for a functional RNA’ or ‘codes for rRNA/tRNAs’ or ‘codes for a sequence of amino acids/primary structure’ Question Marking Guidance Mark Comments 01.2 1. Pre-mRNA (only) produced in eukaryote (cell); 2. Splicing (only) occurs in eukaryote (cell); 3. Introns removed in eukaryote (cell) OR Introns not present in prokaryote (cell); 2 max (2 x AO1) Question Marking Guidance Mark Comments 01.3 1. PNA is complementary to DNA OR PNA forms base pairs with DNA; 2. Preventing/reducing RNA polymerase activity/binding OR Prevents RNA nucleotides binding OR Reducing/stopping transcription; 2 (2 x AO2) Question Marking Guidance Mark Comments 01.4 1. Releases/provides energy; 2. (So) peptide bonds form between amino acids OR (So) amino acid joins to tRNA; 2 (2 x AO1) 1. Reject ‘produce energy’ MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 6 Question Marking Guidance Mark Comments 02.1 Isomer(ism); 1 (AO1) Accept phonetic spelling Ignore structural Question Marking Guidance Mark Comments 02.2 High(er) absorbance (has more sugar) OR Low(er) transmission (has more sugar); 1 (AO2) Accept a description of absorbance or transmission Question Marking Guidance Mark Comments 02.3 1. Benedict’s (solution) volume; 2. Benedict’s (solution) concentration; 3. (Fruit) juice volume; 4. (Water bath/water/solution) temperature; 5. Duration of heating (in water bath); 2 max (2 x AO2) Accept examples of volumes and concentrations and temperatures Question Marking Guidance Mark Comments 02.4 Correct answer for 2 marks = 12;; Accept for 1 mark, 30 (correct mass of apple core) OR 150 (correct mass of apple flesh) OR 8 8 0.08 / 100 × incorrect mass calculated using the ratio OR 14.4 (correct mass in whole apple); 2 (2 x AO2) MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 7 Question Marking Guidance Mark Comments 02.5 1. Starch hydrolysed; 2. Maltose is soluble, (so reduces Ψ) OR Starch is insoluble; 2 (2 x AO2) 2. Accept glucose for maltose 2. Ignore sugar MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 8 Question Marking Guidance Mark Comments 03.1 1. Microvilli increase surface area for diffusion/facilitated diffusion/active transport/co-transport OR Microvilli increase surface area for (more) channel/carrier proteins; 2. (Many) mitochondria release energy/ATP for active transport; 2 (2 x AO2) 1. Accept folded cell (surface) membrane or brush border for microvilli 1. Accept high/large for ‘increased’ 1. Accept ‘they’ for microvilli 2. Accept ‘uptake’ for ‘transport’ 2. Accept ‘cotransport’ for ‘active transport’ Question Marking Guidance Mark Comments 03.2 Correct answer for 2 marks, 40–41(:1);; Accept for 1 mark, 0.32–0.33 (correct surface area of a microvillus) OR 321–322 (correct cell surface area) OR Ratio not simplified e.g. 321:8; 2 (2 x AO2) Question Marking Guidance Mark Comments 03.3 1. ZO-1 is located in cell (surface) membrane; 2. Antibody is complementary (to ZO-1); 3. (So) binds/attaches to the ZO-1/protein; 4. (Cells identified with) dye/stain/ fluorescent marker linked to antibody; 3 max (3 x AO2) 2. and 3. Reject ‘active site’ once 3. Accept ‘forms antigen-antibody complex’ 4. Accept attachment of coloured substance to antibody, but ‘colour production’ on its own is insufficient. 4. ‘Marker’ on its own is insufficient. MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2022 9 Question Marking Guidance Mark Comments 04.1 1. DNA replication (during late interphase); 2. Two divisions; 3. Separation of homologous chromosomes (in first division); 4. Separation of (sister) chromatids (in second division); 5. Produces 4 (haploid) cells/nuclei; 4 max (4 x AO1) 2. Accept for ‘two divisions’, meiosis I and meiosis II OR examples of stages, e.g. [Show More]

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