Multiple Choice
Which component of the genetic code differs between DNA and RNA?
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15. Gene Expression
Genetic Code
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Which mRNA codon is typically found in the A site of the ribosome during translation?
A
The start codon AUG
B
The codon that was just translated
C
The codon that is currently being translated
D
The stop codon UAA
Verified step by step guidance1
Understand the structure of the ribosome during translation: The ribosome has three sites for tRNA binding - the A (aminoacyl), P (peptidyl), and E (exit) sites.
Recognize the role of the A site: The A site is where the incoming aminoacyl-tRNA binds, carrying the next amino acid to be added to the growing polypeptide chain.
Identify the mRNA codon in the A site: The mRNA codon in the A site is the one currently being translated, as it pairs with the anticodon of the incoming tRNA.
Differentiate between the start, stop, and translated codons: The start codon AUG initiates translation, while stop codons (UAA, UAG, UGA) terminate it. The codon in the A site is neither the start nor stop codon but the one being actively translated.
Conclude that the mRNA codon in the A site is the one currently being translated, as it is responsible for determining which tRNA and corresponding amino acid will bind next.
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