Methylation, Histone Marks and Heritable Expression States · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Marks the cell copies, not just the code

Science · Genetics & Evolution · ages 20-22
Name ______________________   Date ____________

  1. What does histone acetylation usually do?

    • Tightens wrapping further
    • Deletes the promoter
    • Loosens wrapping and favors transcription

  2. What does cytosine methylation at a promoter usually do?

    • Loosens wrapping for firing
    • Compacts the region and quiets it
    • Rewrites the base letters

  3. An epigenetic change leaves the base sequence identical while altering how it is read.

    Circle one:   True   False

  4. Two cells share identical sequences but express a gene differently. What best explains it?

    • Different access marks on the same letters
    • A hidden mutation
    • Different numbers of chromosomes

  5. Right after replication, a DNA duplex is half marked. What happens next?

    • The marks are erased everywhere
    • Maintenance enzyme marks the new strand to match
    • The sequence letters get rewritten

  6. A diet signal in a progenitor alters descendants long after the diet ends. Why?

    • The diet rewrote base letters
    • Maintenance copying preserved rewritten marks in descendants
    • Descendants kept eating the diet

  7. A methylated promoter sits beside abundant activator proteins. What happens?

    • The gene fires at full speed
    • The gene stays quiet because factors cannot reach it
    • The activators rewrite the sequence

  8. A student sequences a quiet gene, finds no mutation, and declares the DNA normal. What is the error?

    • Sequencing always finds marks
    • No mutation rules out regulation
    • Methylation and histone state are invisible to plain sequencing
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Answer key

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

Marks the cell copies, not just the code W1-mt_QIEjt77tjV-s1

  1. Loosens wrapping and favors transcription · Acetyl marks open the wrapping so machinery can reach in.
  2. Compacts the region and quiets it · Methylation recruits binders that pack the region shut.
  3. True · Only marks and access change, never the letters themselves.
  4. Different access marks on the same letters · Same letters with different gating give different firing.
  5. Maintenance enzyme marks the new strand to match · The enzyme recognizes the half marked state and copies the pattern.
  6. Maintenance copying preserved rewritten marks in descendants · Copying carries the new settings forward with no fresh input.
  7. The gene stays quiet because factors cannot reach it · A shut gate excludes factors no matter how abundant they are.
  8. Methylation and histone state are invisible to plain sequencing · Marks need their own assays, so quiet genes can hide there.
Worksheet · LightMySky