Transcription Factors and Epigenetic Control · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How identical DNA makes different cells

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

  1. What does adding methyl groups to DNA usually do?

    • It deletes the gene from the chromosome
    • It silences the gene reversibly
    • It copies the gene to another chromosome

  2. What do transcription factors do?

    • They rewrite the DNA base sequence
    • They bind DNA and tune the transcription rate
    • They carry finished proteins out of the nucleus

  3. An epigenetic change alters the DNA base sequence.

    Circle one:   True   False

  4. A gene sits in tightly packed chromatin. What follows for its expression?

    • It is read faster than ever
    • It stays hidden and switches off
    • It is copied into every daughter genome twice

  5. How do activators and repressors differ?

    • Activators invite polymerase in, repressors block the site
    • Activators cut DNA, repressors glue it back
    • Activators work only in nerves, repressors only in liver

  6. Why do liver and nerve cells make different proteins from identical DNA?

    • They carry different genomes from birth
    • They read different gene sets via factors and marks
    • Liver cells lack a nucleus entirely

  7. A heritable trait passes to daughter cells with the DNA sequence unchanged. What explains it?

    • A point mutation in the coding region
    • A deleted chromosome segment
    • An epigenetic mark on chromatin state

  8. A student says histone acetylation tightens packing and silences genes. What is wrong?

    • Acetylation loosens packing and exposes genes
    • Histones never touch DNA at all
    • Packing has no effect on transcription
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Answer key

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

How identical DNA makes different cells W1-mt_nF4JJ_EDa4-s1

  1. It silences the gene reversibly · Methylation hushes a gene, and removing the marks can switch it back on.
  2. They bind DNA and tune the transcription rate · Factors grip regulatory DNA and raise or lower how fast a gene is read.
  3. False · Epigenetic marks change access to genes while the letters stay identical.
  4. It stays hidden and switches off · Tight packing hides the gene from factors and polymerase.
  5. Activators invite polymerase in, repressors block the site · Activators help RNA polymerase dock and start, while repressors stall it.
  6. They read different gene sets via factors and marks · Different factors and marks switch different chapters on in each cell type.
  7. An epigenetic mark on chromatin state · Marks on DNA and histones are inherited without rewriting any letters.
  8. Acetylation loosens packing and exposes genes · Acetyl groups relax histone grip so the machinery can reach the gene.
Worksheet · LightMySky