Alternative Splicing and One Gene, Many Proteins · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One gene, many proteins

Science · Biochemistry & Molecular Biology · ages 20-21
Name ______________________   Date ____________

  1. Which marks tell the spliceosome where to cut?

    • Start and stop codons
    • Promoters and enhancers
    • Consensus sites plus a branch point adenosine

  2. What does the spliceosome remove from a fresh transcript?

    • The exons
    • The introns
    • The finished protein

  3. Skipping a cassette exon changes which protein domains the final protein carries.

    Circle one:   True   False

  4. A gene has three cassette exons, each either kept or skipped. Type how many possible transcripts that gives.

    Answer: ______________

  5. A gene has two cassette exons, each either kept or skipped. How many combinations exist?

    • Two
    • Four
    • Six

  6. A mutation destroys a normal splice site but alters no codon. What happens?

    • Splicing proceeds exactly as before
    • A cryptic site is used or an exon is skipped
    • The gene is deleted outright

  7. A student calls a splice site variant a coding change because the protein differs. What is the error?

    • Proteins never change from splicing
    • Only codons count as genes
    • The codons are intact, so the change is in exon assembly

  8. A tissue raises its hnRNP level while SR stays flat. What shifts?

    • Sites hnRNP suppresses get used less
    • All sites get used more
    • Splicing stops needing consensus marks
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Answer key

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

One gene, many proteins W1-mt_xei9v3IIsE-s1

  1. Consensus sites plus a branch point adenosine · The 5 prime site, branch point, and 3 prime site aim the chemistry.
  2. The introns · It cuts every intron at consensus marks and joins the exons.
  3. True · Each exon kept or dropped swaps domains in or out.
  4. 8 · Three doublings give two times two times two, which is eight.
  5. Four · Each cassette doubles the set: two times two is four.
  6. A cryptic site is used or an exon is skipped · Losing the site reroutes the choice while codons stay untouched.
  7. The codons are intact, so the change is in exon assembly · The variant reroutes site choice, and the exon set change alters the protein.
  8. Sites hnRNP suppresses get used less · hnRNP proteins suppress nearby sites, so their targets fade.
Worksheet · LightMySky