Chromatin: Nucleosomes and Higher-Order Packing · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Packing two metres of DNA into a nucleus

Science · Genetics & Evolution · ages 18-20
Name ______________________   Date ____________

  1. How many histone proteins form one bead core?

    • Eight
    • Two
    • Thirty

  2. Which order runs from smallest to largest packing?

    • Chromosome, fibre, bead, helix
    • Helix, nucleosome bead, fibre, chromosome
    • Bead, helix, chromosome, fibre

  3. Tightly packed regions hold genes that are absent.

    Circle one:   True   False

  4. One gene copy is read, its twin is quiet. What differs?

    • The quiet copy has vanished
    • The quiet copy sits in tighter packing
    • The quiet copy left the nucleus

  5. Why does a histone grip two different sequences alike?

    • It reads each letter twice
    • It cuts the backbone first
    • It clings by charge, not by letters

  6. A stretch loosens from fibre to loose beads. What happens to reading?

    • Reading rises as machinery can land
    • Reading stops since beads repel ink
    • Reading moves to another cell

  7. Since histones bind by charge, changing the letters always frees the DNA.

    Circle one:   True   False

  8. A test shows low RNA from a region, and a friend claims its genes are deleted. What is the flaw?

    • RNA tests never work at all
    • Deleted genes always read loudly
    • Low reading may mean tight packing, not loss
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Answer key

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

Packing two metres of DNA into a nucleus W1-mt_5q3Hsdqm9x-s1

  1. Eight · Eight histones form the core of each bead.
  2. Helix, nucleosome bead, fibre, chromosome · Packing grows: helix, beads, fibre, chromosome.
  3. False · Tight means unread, not gone.
  4. The quiet copy sits in tighter packing · Tight coils block the reading machinery.
  5. It clings by charge, not by letters · Charge attraction ignores the letter order.
  6. Reading rises as machinery can land · Looser packing opens landing room for the machinery.
  7. False · Charge grip holds whatever the letters say.
  8. Low reading may mean tight packing, not loss · Low output fits closed packing with genes intact.
Worksheet · LightMySky