The Shine–Dalgarno sequence
How do prokaryotic ribosomes find the correct start codon on an mRNA?
Answer A: explanation for every choice
A
Correct. Base pairing between 16S rRNA and the Shine–Dalgarno sequence positions the start codon in the ribosome.
B
Cap-dependent scanning is how eukaryotic ribosomes find the start codon.
C
Prokaryotic mRNA typically lacks a poly-A tail used for initiation.
D
Prokaryotic genes generally lack introns.
TakeawayProkaryotes: Shine–Dalgarno. Eukaryotes: 5′ cap and scanning.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb133.