Transcription and RNA Splicing in Eukaryotes · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

From gene to edited message

Science · Genetics & Evolution · ages 16-17
Name ______________________   Date ____________

  1. Which parts of a gene survive splicing?

    • The terminator sequence
    • Exons, joined into one message
    • Introns, joined into one message

  2. What does RNA polymerase build as it reads the template strand?

    • pre-mRNA, the rough first copy
    • A new DNA double helix
    • A protein chain

  3. Introns are cut out before mRNA leaves the nucleus.

    Circle one:   True   False

  4. A cap and a tail are added to pre-mRNA. What are they for?

    • To copy the DNA a second time
    • To join amino acids together
    • To protect the message and mark it ready to leave

  5. A template strand reads TAC. What does the matching RNA read?

    • AUG
    • TAC
    • CAT

  6. Nerve and muscle cells share a gene but make different proteins. What best explains this?

    • Their DNA sequences differ
    • One of them skips transcription
    • They splice its exons in different patterns

  7. A drug jams the spliceosome. What builds up, and what runs short?

    • DNA copying speeds up instead
    • Uncut pre-mRNA builds up, while mature mRNA runs short
    • Extra ribosomes are built

  8. A student claims the mRNA leaving the nucleus is longer than its gene because of splicing. What is wrong?

    • Splicing removes introns, so the mRNA is shorter
    • Splicing adds extra genes to the message
    • The cap and tail carry the lost introns
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Answer key

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

From gene to edited message W1-mt_j2vc70vH5t-s1

  1. Exons, joined into one message · Exons are kept and joined. Introns are cut out.
  2. pre-mRNA, the rough first copy · It copies the gene into pre-mRNA, which still needs editing.
  3. True · Splicing happens in the nucleus, so introns never leave it.
  4. To protect the message and mark it ready to leave · They guard the ends and mark the message ready to exit.
  5. AUG · Pair each base: T with A, A with U, C with G.
  6. They splice its exons in different patterns · Same gene, different exon choices. That is alternative splicing.
  7. Uncut pre-mRNA builds up, while mature mRNA runs short · No cutting means no finished messages, so pre-mRNA piles up.
  8. Splicing removes introns, so the mRNA is shorter · Cutting introns out can only shorten the message, never lengthen it.
Worksheet · LightMySky