1. The diagram below shows the process of translation.

Transcription

1 1. The diagram below shows the process of translation. Page 1 of 9

2 Which statement correctly identifies and describes the role of a structure shown in the diagram that is involved in translation? (A) Structure W is mrna, which is involved in converting the nucleic acid code into an amino acid sequence. This answer suggests the student may understand that mrna codons are translated into amino acids, but does not understand that the structure indicated is a trna molecule because it is transporting the amino acid that matches the RNA codon on the mrna to the ribosome. (B) Structure X is the A site on the ribosome, which is composed of rrna and proteins, and is involved in the pairing of RNA codons with trna anticodons. Rationale: This answer suggests the student understands that the A site on the ribosome is composed of rrna and protein and helps to pair specific trna anticodons with mrna codons so that the proper amino acid can be attached to the polypeptide chain. (C) Structure Y is trna, which reads the nucleic acid code and assembles the polypeptide. This answer suggests the student may understand that trna plays a role in translation by reading the codons on mrna, but does not understand that the structure indicated is a polypeptide chain and not trna because trna is not composed of amino acids. (D) Structure Z is a growing polypeptide chain that is being synthesized by trna and rrna, and that will be folded and moved to its final location in or out of the cell. This answer suggests the student may understand that polypeptides are synthesized based on the interaction of rrna and trna molecules assembling specific amino acids into a chain, but does not understand that structure Z is mrna and not a polypeptide because polypeptides are not composed of nucleotides and do not pair with trna anticodons. Aligned to: LO 3.4 CA 3.4: Represent Genetic Information Page 2 of 9

3 2. The table below shows the relationship between mrna codons and their amino acids. Which mrna segment shows the correct base sequence and directionality to produce the amino acid sequence Met-Pro-Tyr-Ser-Leu-Ile? (A) 5'-AUG CCC UAG UCC CUG AUC-3' This answer suggests the student may understand that mrna is transcribed in the 5' 3' direction and that AUG is the start codon, but does not understand that this mrna sequence will not produce the given polypeptide because UAC codes for a stop codon and not the amino acid Tyr. (B) 3'-AUG CCG UAC UCG CUA AUA-5' This answer suggests the student may understand how to convert mrna codons to the appropriate amino acids in translation, but does not understand that mrna is always translated in the 5' 3' direction. Page 3 of 9

4 (C) 5'-AUG CCA UAU UCC CUG AUC-3' Rationale: This answer suggests the student understands that mrna is transcribed in the 5' 3' direction and how to convert mrna codons to the appropriate amino acids in transcription. (D) 3'-AUG CCU UAU AGC CUG AUU-5' This answer suggests the student may understand how to convert mrna codons to the appropriate amino acids in translation, but does not understand that mrna is always translated in the 5' 3' direction. Aligned to: LO 3.4 CA 3.4: Represent Genetic Information 3. The table below shows how mrna codons are translated into amino acids. Page 4 of 9

5 A base substitution in which a guanine (G) base is replaced with a cytosine (C) base occurs on the DNA template shown below. Which statement best predicts what will happen to the polypeptide that is translated from this altered DNA template? (A) The substitution will result in no change in the polypeptide, because only the third base in the affected codon will be changed, and only the first two bases in a codon determine the amino acid that is translated. This answer suggests the student may understand that the third base is not as influential as the first and second bases in determining the translated amino acid in many mrna codons, but does not understand that this substitution will cause a significant change in the given polypeptide sequence because this substitution changes the original codon to a stop codon. (B) The substitution will result in a change in the second amino acid to Ile, because the codon will be changed to AUC, which codes for the amino acid Ile. This answer suggests the student may understand that the amino acid translated from the affected codon will change as a result of the base substitution, but does not understand that the polypeptide will stop because the anticodon that pairs with the codon UAG is a stop codon. (C) The substitution will result in only one amino acid being translated, because the second codon will be changed to a stop codon, and translation will immediately stop. Page 5 of 9

6 Rationale: This answer suggests the student understands that this base substitution would result in the transcription of the codon UAG, which is a stop codon and would stop polypeptide synthesis. (D) The substitution will result in a change in all of the amino acids after the substitution, because the new base will also change the codons translated after the substitution. This answer suggests the student may understand that the base substitution changes the affected codon, but does not understand that although translation of all of the codons downstream of the substitution is stopped prematurely, the actual codons will remain unchanged. Aligned to: LO 3.4 CA 3.4: Represent Genetic Information Page 6 of 9

7 4. The table below shows how mrna codons are translated into amino acids. Three bases are deleted in the mrna sequence shown below. Page 7 of 9

8 Which statement best predicts the effect of the deletion on the resulting polypeptide? (A) The third amino acid will be deleted from the polypeptide, but all other amino acids will remain unchanged, because the second codon will still code for the same amino acid and no other codons will be affected. Rationale: This answer suggests the student understands that a deletion of the three bases shown would result in a shift of the bases so that the second codon still codes for arginine (CGU and CGC both code for the Arg amino acid), and that the third amino acid would be removed from the polypeptide. (B) The second and third amino acids will be deleted from the polypeptide, but all other amino acids will remain unchanged, because only the second and third codons will be affected by the deletion. This answer suggests the student may understand that the second and third codons are affected by the deletion, but does not understand that this deletion does not change the second amino acid and deletes the third, because the mrna bases will shift, and that, while the second codon will change, it will still code for the same amino acid (CGU and CGC both code for the Arg amino acid). (C) All of the amino acids after the first will be changed in the polypeptide, because the deletion will create a shift beginning with the second, and this will change all codons that follow. This answer suggests the student may understand that most deletions result in a frameshift where all codons that follow the deletion are no longer functional, but does not understand that this particular deletion of a triplet is an exception and does not cause a frameshift because each codon is a triplet and because change in the second codon will result in the same amino acid (CGU and CGC both code for the Arg amino acid). (D) The Leu amino acid will be deleted from the polypeptide, but all other amino acids will remain unchanged, because when only one codon is removed, all other codons will remain unchanged. Page 8 of 9

9 This answer suggests the student may understand that the codon UUG codes for a leucine (Leu) amino acid, but does not understand that the deletion occurred between two codons that code for other amino acids and that UUG was not a codon in the original sequence. Aligned to: LO 3.4 CA 3.4: Represent Genetic Information Page 9 of 9