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8.4 Recombinant DNA MS - mark scheme

mark scheme
Module

Biology (BIO00068H)

11 Documents
Students shared 11 documents in this course
Academic year: 2022/2023
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University of York

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Mark schemes

Q1.

(a) 1. Restriction endonucleases/enzymes cuts plasmid;

OR

Restriction endonucleases/enzymes produces ‘sticky ends’; Ignore restriction enzymes cuts out the gene. Reject restriction enzymes cuts the gene.

  1. Ligase joins gene/DNA and plasmid

OR

Ligase joins ‘sticky ends’; 2

(b) 1. Cell division has occurred (before gene added); Accept mitosis but reject meiosis.

  1. (Cells producing) gametes do not receive the gene; Accept DNA replication has occurred. 2

(c) 1. No overlap in SDs;

  1. Significant increase/difference (in growth/mass)

OR

Increase/difference (in growth/mass) is not due to chance; Reject ‘the results are significant or not due to chance’. 2

(d) 1. Large sample size so representative;

  1. 12 months so can assess/allow growth; Accept long time for 12 months. Accept increase in mass for growth.

  2. Control (present) for comparison; Accept description of the control. 2 max [8]

Q2.

(d) Binds to P34 gene/DNA/mRNA OR

Binds to transcription factor gene/DNA OR Binds to promoter; Reject binds to transcription factor 1

(e) 1. Restriction (endonuclease/enzyme) to cut plasmid/vector;

  1. Ligase joins gene/DNA to plasmid/vector; 2

(f) 1. Mass/number of amino acids/polypeptides; Accept weight for mass Ignore density/size Accept length of polypeptide/amino acid chain Accept primary structure /sequence of amino acids. Accept tertiary structure

  1. Charge;

  2. R groups (differ); 2 max

Q3.

(a) Produces (c)DNA using (m)RNA; Accept: ‘converts’ (m)RNA to (c)DNA. Reject: tRNA 1

(b) Joins nucleotides to produce (complementary strand/s of) DNA; Accept: ‘joins DNA nucleotides’. 1

(c) 1. To remove any DNA present; 2. As this DNA would be amplified / replicated; 1. Must be idea of removal / destruction. 2. Accept: idea of DNA not being used as template. 2

(d) 1. Ratio in range of 1 :1 to 1 :1 = 2 marks; 2. One mark for answers which shows incorrect ratio but Shows 0 as a number or line on the graph OR Ratio in correct range, but the wrong way round OR Ratio in correct range but not expressed to 1 OR Ratio shown the other way round in range 1: 0 to 1:0; Note: ratio not expressed to 1 in correct range may be shown in different ways, for example as:

Q5.

(a) 1. (If injected into egg), gene gets into all / most of cells of silkworm; 2. So gets into cells that make silk. 2

(b) 1. Not all eggs will successfully take up the plasmid; 2. Silkworms that have taken up gene will glow. 2

(c) Promoter (region / gene). 1

(d) 1. So that protein can be harvested; 2. Fibres in other cells might cause harm. 2 [7]

Q6.

(a) 1. (Requires DNA fragment) DNA polymerase, (DNA) nucleotides and primers;

  1. Heat to 95 °C to break hydrogen bonds (and separate strands); Accept temperature in range 90 to 95 °C.

  2. Reduce temperature so primers bind to DNA/strands; Accept temperature in range 40 to 65 °C.

  3. Increase temperature, DNA polymerase joins nucleotides (and repeat method); Accept Taq polymerase for DNA polymerase. Accept temperature in range 70 to 75 °C. 4

(b) 1. (Initially) number (of molecules) doubling is low

OR

Doubles each cycle to produce exponential increase; First alternative relates to idea of low numbers i., 2, 4, 8, 16, 32 etc.

  1. Plateaus as no more nucleotides/primers; Accept ‘levels out’ or ‘flattens’ for plateaus. Accept enzyme/polymerase (eventually) denatures. 2 [6]
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8.4 Recombinant DNA MS - mark scheme

Module: Biology (BIO00068H)

11 Documents
Students shared 11 documents in this course

University: University of York

Was this document helpful?
Mark schemes
Q1.
(a) 1. Restriction endonucleases/enzymes cuts plasmid;
OR
Restriction endonucleases/enzymes produces ‘sticky ends’;
Ignore restriction enzymes cuts out the gene.
Reject restriction enzymes cuts the gene.
2. Ligase joins gene/DNA and plasmid
OR
Ligase joins ‘sticky ends’;
2
(b) 1. Cell division has occurred (before gene added);
Accept mitosis but reject meiosis.
2. (Cells producing) gametes do not receive the gene;
Accept DNA replication has occurred.
2
(c) 1. No overlap in SDs;
2. Significant increase/difference (in growth/mass)
OR
Increase/difference (in growth/mass) is not due to chance;
Reject ‘the results are significant or not due to
chance’.
2
(d) 1. Large sample size so representative;
2. 12 months so can assess/allow growth;
Accept long time for 12 months.
Accept increase in mass for growth.
3. Control (present) for comparison;
Accept description of the control.
2 max
[8]
Q2.
(d) Binds to P34 gene/DNA/mRNA
OR
AQA Biology A-Level - Recombinant DNA MS PhysicsAndMathsTutor.com

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