Which feature of tRNA ensures correct amino-acid placement during translation?

Answer: Specific anticodon-codon base pairing on mRNA, with cognate amino acid attached at the 3' CCA end. Each tRNA has an anticodon that base-pairs with a complementary mRNA codon and carries the corresponding amino acid (charged by aminoacyl-tRNA synthetase) at its 3' CCA end, providing translation fidelity.

Translation occurs at

Answer: Ribosomes (free or ER-bound) mRNA is decoded at ribosomes — large and small ribosomal subunits plus tRNAs assemble polypeptides.

The fact that several distinct codons can encode the same amino acid (e.g., serine, arginine) is termed:

Answer: Degeneracy (redundancy) of the genetic code The genetic code is degenerate: most amino acids are specified by more than one codon, which buffers many third-position mutations against amino acid changes.

AP Biology · Topic 6.4

Translation Practice

Part of Gene Expression and Regulation.(IST-1.L)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$Which feature of tRNA ensures correct amino-acid placement during translation?$
- A
  $Anticodons recognize the ribosome's E-site directly.$
- B
  $Random recruitment of any amino acid by the A-site.$
- C
  $tRNA reads mRNA 5' to 3' as DNA polymerase does.$
- D
  $Specific anticodon-codon base pairing on mRNA, with cognate amino acid attached at the 3' CCA end.$
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Why
$Each tRNA has an anticodon that base-pairs with a complementary mRNA codon and carries the corresponding amino acid (charged by aminoacyl-tRNA synthetase) at its 3' CCA end, providing translation fidelity.$
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Sample 2difficulty 1/5
$Translation occurs at$
- A
  $Smooth endoplasmic reticulum$
- B
  $Nucleoli (within the nucleus)$
- C
  $Golgi apparatus membranes$
- D
  $Ribosomes (free or ER-bound)$
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Why
$mRNA is decoded at ribosomes — large and small ribosomal subunits plus tRNAs assemble polypeptides.$
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Sample 3difficulty 1/5
$The fact that several distinct codons can encode the same amino acid (e.g., serine, arginine) is termed:$
- A
  $Nonsense$
- B
  $Degeneracy (redundancy) of the genetic code$
  check_circle
- C
  $Wobble at the anticodon's first position$
- D
  $Universal mutation$
Why
$The genetic code is degenerate: most amino acids are specified by more than one codon, which buffers many third-position mutations against amino acid changes.$
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Sample 4difficulty 1/5
$A codon is$
- A
  $A 2-nucleotide pair in DNA that signals replication start$
- B
  $A 3-nucleotide sequence in mRNA that specifies an amino acid (or stop)$
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- C
  $A 3-amino-acid sequence in a polypeptide that determines folding$
- D
  $A regulatory DNA element that binds transcription factors$
Why
$The genetic code: 64 codons specify the 20 amino acids; 3 are stops (UAA, UAG, UGA).$
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Sample 5difficulty 1/5
$The genetic code uses 4 bases (A, U, G, C) in 3-base codons. Total possible codons:$
- A
  $12$
- B
  $64$
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- C
  $256$
- D
  $16$
Why
$4³ = 64 codons.$
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