Translation: read a codon table to build a protein

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   mRNA (model, not to scale), 5′ to 3′, cut into codons: AUG UUU UUC GGA UAG. Table excerpt of the standard genetic code: AUG, methionine; UUU, phenylalanine; UUC, phenylalanine; UUA, leucine; GGA, glycine; UAG, stop.

2. 1.

   Jun translates a cut mRNA with the table excerpt. Which chain of amino acids does it build?

   • methionine, phenylalanine, phenylalanine, glycine, stop
   • methionine, phenylalanine, leucine, glycine
   • methionine, phenylalanine, glycine
   • methionine, phenylalanine, phenylalanine, glycine

3. Use this

   mRNA (model, not to scale), 5′ to 3′, 18 bases, not cut: GCCAUGCCAGUCAAGUGA. Table excerpt of the standard genetic code: GCC, alanine; AUG, methionine; CCA, proline; GUC, valine; AAG, lysine; UGA, stop.

4. 2.

   Kira translates this mRNA with the table excerpt. The ribosome begins at the first AUG. Which amino acid comes third in the chain?

   • methionine, the amino acid for AUG
   • lysine, the amino acid for AAG
   • proline, counting GCC as the first codon
   • valine, the amino acid for GUC

5. Use this

   mRNA (model, not to scale), 5′ to 3′, 20 bases, not cut: GCCAUGGAUACCUGCUAAGU. Table excerpt of the standard genetic code: GCC, alanine; AUG, methionine; GAU, aspartic acid; GAA, glutamic acid; ACC, threonine; UGC, cysteine; UAA, stop.

6. 3.

   Luz translates this mRNA with the table excerpt. The ribosome begins at the first AUG. Which chain does it build?

   • methionine, aspartic acid, threonine, cysteine, stop
   • alanine, methionine, aspartic acid, threonine, cysteine
   • methionine, glutamic acid, threonine, cysteine
   • methionine, aspartic acid, threonine, cysteine

7. Parts card (model data)

   part of the mRNA	bases
   before AUG	6
   from AUG to the end of the stop codon	42
   after the stop codon	9

8. 4.

   Noah reads a parts card for a model mRNA. The ribosome begins at AUG and ends at the stop codon. How many amino acids are in the chain?

   • 19 amino acids, from the 57 bases of the whole mRNA
   • 14 amino acids, one for each of the 14 codons
   • 13 amino acids: 14 codons less the stop
   • 21 amino acids, one for each pair of bases

9. Chain card (model data)

   item	amount
   amino acids in the chain	8

10. 5.

    Pia's model mRNA builds a chain of 8 amino acids. How many bases run from AUG to the end of the stop codon?

    • 24 bases, one codon for each of the 8 amino acids
    • 27 bases: 8 amino acid codons and a stop codon
    • 16 bases, two bases for each amino acid
    • 8 bases, one base for each amino acid

11. Use this

    Two mRNAs (model, not to scale), 5′ to 3′, cut into codons. Message P: AUG UUU GGC UAA. Message Q: AUG UUC GGC UAA. Table excerpt of the standard genetic code: AUG, methionine; UUU, phenylalanine; UUC, phenylalanine; GGC, glycine; UAA, stop.

12. 6.

    Ren compares two model mRNAs, P and Q, with the table excerpt. Which statement is true about the chains they build?

    • Different chains, because Q is missing a codon
    • The same chain, because UUU and UUC both code for phenylalanine
    • Different chains, because different codons add different amino acids
    • The same chain, because both messages have four codons

13. Fact card (textbook facts)

    item	number
    combinations of two bases	16
    combinations of three bases	64
    amino acids in proteins	20

14. 7.

    Zee reads a fact card about the genetic code. Which statement shows that a codon cannot be two bases long?

    • Three bases give only 16 combinations, fewer than the 20 amino acids
    • Two bases give only 16 combinations, fewer than the 20 amino acids
    • Two bases give 64 combinations, more than the 20 amino acids
    • Two bases are enough, since 16 combinations come close to 20

15. Use this

    mRNA (model, not to scale), 5′ to 3′, cut into codons: AUG GCC UGG UAA. Each anticodon is written 3′ to 5′ under its codon.

16. 8.

    Ari lists the tRNA anticodons for the codons before the stop codon. Which list is right, in order?

    • UAC, CGG, ACC, AUU
    • TAC, CGG, ACC
    • UAC, CGG, ACC
    • AUG, GCC, UGG

17. Use this

    tRNA anticodon (model, not to scale), 3′-CGA-5′. It pairs with the mRNA codon under the ribosome: ? ? ?. Table excerpt of the standard genetic code: GCU, alanine; CGA, arginine; AGC, serine; UGC, cysteine.

18. 9.

    Bo follows a tRNA with the anticodon 3′-CGA-5′ to the ribosome. Which amino acid does that tRNA bring?

    • cysteine, from the codon UGC
    • arginine, from reading CGA in the table
    • alanine, from the codon GCU
    • serine, from reading AGC in the table

19. Use this

    mRNA (model, not to scale), 5′ to 3′, cut into codons: AUG CCU UGA GGA. Table excerpt of the standard genetic code: AUG, methionine; CCU, proline; UGA, stop; GGA, glycine.

20. 10.

    Esme follows the ribosome to the stop codon UGA. Which anticodon does a matching tRNA carry?

    • AUG, because a stop codon uses the start tRNA
    • UGA, because the anticodon copies the codon
    • ACU, because each base pairs with its partner
    • None, because no tRNA pairs with a stop codon