PCR, Electrophoresis and DNA Profiling · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Copy It, Sort It, Match It

Science · Genetics & Evolution · ages 17-18
Name ______________________   Date ____________

  1. Gel electrophoresis sorts DNA fragments by their what?

    • Length
    • Gene
    • Charge

  2. What does the high heat step of PCR do?

    • It docks the primers onto the DNA
    • It splits the two DNA strands apart
    • It builds the fresh DNA strands

  3. A DNA profile compares which part of the genome?

    • Whole genes read end to end
    • The full genome letter by letter
    • Repeat counts at chosen stretches

  4. One target strand goes through 10 PCR cycles. Each cycle doubles the DNA. How many copies are there now?

    Answer: ______________

  5. Put the three PCR temperature steps in order.

    • Split, dock primers, build new strands
    • Build new strands, split, dock primers
    • Dock primers, build new strands, split

  6. Two fragments run on one gel. Which ends up nearer the positive end?

    • Both stop together halfway
    • The longer fragment
    • The shorter fragment

  7. A sample holds only a few strands of DNA. What should you do before running a gel?

    • Read the whole genome directly
    • Copy the target many times with PCR
    • Heat the sample until bands appear

  8. A student says two matching gene sequences must give matching band patterns. This claim is true.

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Copy It, Sort It, Match It W1-mt_Sv1jV0XnsX-s1

  1. Length · Every fragment has the same charge, so only length decides how far each piece moves.
  2. It splits the two DNA strands apart · Heat breaks the pairing between the strands so that copying can start.
  3. Repeat counts at chosen stretches · Profiles compare how many times a short sequence repeats, since that varies between people.
  4. 1024 · Doubling ten times turns 1 copy into 1024 copies.
  5. Split, dock primers, build new strands · Split first, then dock the primers, then let Taq build, and repeat.
  6. The shorter fragment · Short pieces slip through the mesh faster, so they travel further toward the positive end.
  7. Copy the target many times with PCR · A gel needs far more DNA than a few strands, and PCR supplies those copies.
  8. False · Bands show repeat counts, which vary between people even when the genes match.
Worksheet · LightMySky