Lesson 6.1.2

6.1.2 DNA profiling and PCR amplification Quiz: Pearson Edexcel Biology, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.2, DNA profiling and PCR amplification: 20 multiple choice questions for the Pearson Edexcel Biology (9BI0), Unit 6: Immunity, Infection and Forensics, written with Revision Ninja.

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The 20 questions

  1. Which technique amplifies a small sample of DNA into millions of copies?

    • DNA profiling
    • Gel electrophoresis
    • Polymerase chain reaction
    • Southern blotting

  2. Which stage of PCR involves heating to separate double-stranded DNA?

    • Annealing
    • Extension
    • Polymerisation
    • Denaturation

  3. Why is Taq polymerase used in PCR instead of human DNA polymerase?

    • Prevents primer annealing
    • Resists high temperatures
    • Synthesises RNA strands
    • Denatures at 95°C

  4. What is the primary role of primers in a PCR mixture?

    • Provide attachment sites
    • Denature template DNA
    • Digest excess nucleotides
    • Break hydrogen bonds

  5. Starting with one DNA molecule, how many copies are produced after 20 PCR cycles?

    • 1,048,576
    • 2,097,152
    • 400,000
    • 20,000

  6. Towards which electrode do DNA fragments move during gel electrophoresis?

    • Negative electrode
    • Neutral pole
    • Cathode
    • Anode

  7. What is the main purpose of using a DNA ladder during gel electrophoresis?

    • Estimate fragment sizes
    • Prevent DNA degradation
    • Stain DNA bands
    • Provide electric current

  8. Which regions of DNA are primarily analysed during standard DNA profiling?

    • Protein-coding genes
    • Exons
    • Centromeres
    • Short tandem repeats

  9. What indicates a close genetic relationship between two individuals on a DNA profile?

    • Higher total mass
    • Identical band counts
    • Matching band positions
    • Different band intensity

  10. What name is given to the PCR stage where primers bind to DNA?

    • Annealing
    • Transcription
    • Extension
    • Denaturation

  11. Why must contamination be strictly avoided during a PCR preparation?

    • Taq polymerase degrades
    • Primers become toxic
    • Buffer breaks down
    • Foreign DNA amplifies

  12. What does an absent band in a PCR negative control indicate?

    • Target sequence mutated
    • Enzyme was inactive
    • No contamination present
    • PCR run failed

  13. What risk is increased when performing PCR on highly degraded DNA samples?

    • Enzyme denaturation
    • Excessive base pairing
    • Contamination impact
    • Higher gel voltage

  14. Why is the amplification of DNA during PCR described as exponential?

    • Linear mass increase
    • Copy number triples
    • Rate slows down
    • Copy number doubles

  15. Which factor directly affects the statistical probability of a DNA match being coincidental?

    • Buffer concentration
    • Gel electrophoresis voltage
    • Number of STRs
    • PCR cycle count

  16. Which specific molecule is synthesized during the extension stage of PCR?

    • Messenger RNA molecules
    • Complementary DNA strands
    • Polypeptide chains
    • Single-stranded RNA

  17. What role do magnesium ions play in a PCR mixture?

    • Primer binding sequence
    • DNA strand template
    • Gel matrix stain
    • Taq polymerase cofactor

  18. How many PCR cycles are required to produce at least 1,000 copies from one template DNA strand?

    • 8
    • 10
    • 500
    • 100

  19. What main factor determines how far a DNA fragment travels through agarose gel during electrophoresis?

    • Phosphate charge
    • Fragment length
    • Gel temperature
    • Base composition

  20. What is the role of the template strand in a PCR reaction mixture?

    • Strand being copied
    • Nucleotide source
    • Primer molecule
    • Enzyme catalyst

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