Translation at the Ribosome · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading codons, building proteins

Science · Genetics & Evolution · ages 16-18
Name ______________________   Date ____________

  1. What docks at each codon during elongation?

    • A new ribosome subunit
    • A DNA polymerase
    • A tRNA with a matching anticodon

  2. How many bases make one codon?

    • Two
    • Three
    • Four

  3. AUG is the start codon and adds methionine.

    Circle one:   True   False

  4. A message reads AUG, then CUA, then a stop codon. How many amino acids are released?

    • Three
    • Two
    • One

  5. An mRNA codon reads CUA. Which anticodon pairs with it?

    • CUA
    • GAU
    • GAT

  6. A mutation swaps only the third base of a codon, and the protein stays the same. What explains this?

    • Alternative splicing
    • A shifted reading frame
    • Degeneracy of the genetic code

  7. No tRNA fits the stop codon. What happens next?

    • A random amino acid is added
    • The finished chain is released
    • The ribosome reads backwards

  8. A student says codons overlap by one base as the ribosome reads. What is wrong?

    • The message slides a full codon each step, so triplets never overlap
    • tRNAs would run out of amino acids
    • Stop codons would vanish from the message
LightMySky · lightmysky.comW1-mt_1EdZzeqts1-s1

Answer key

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

Reading codons, building proteins W1-mt_1EdZzeqts1-s1

  1. A tRNA with a matching anticodon · Each tRNA pairs its anticodon and delivers its amino acid.
  2. Three · Codons are triplets, read three at a time.
  3. True · Reading begins at AUG, which brings methionine first.
  4. Two · Methionine plus one more, then the stop releases the chain of two.
  5. GAU · Pair up C with G, U with A, A with U.
  6. Degeneracy of the genetic code · Many codons share an amino acid, often differing only at the third base.
  7. The finished chain is released · With nothing to add, the subunits part and the chain folds.
  8. The message slides a full codon each step, so triplets never overlap · Overlapping reads would scramble every codon after the first.
Worksheet · LightMySky