What is the Shine–Dalgarno sequence?

• A. A promoter element found in eukaryotic genes
• B. A ribosomal binding site in bacterial mRNA that helps initiate translation
• C. A region of tRNA responsible for amino acid attachment
• D. A DNA sequence that signals the termination of transcription in eukaryotes

Answer: (B)

Verified step by step guidance

1. Understand that the Shine–Dalgarno sequence is related to the process of translation, which is the synthesis of proteins from mRNA.
2. Recall that in bacteria, translation initiation requires the ribosome to bind to a specific site on the mRNA to start protein synthesis.
3. Identify that the Shine–Dalgarno sequence is a short nucleotide sequence found in bacterial mRNA, located upstream of the start codon.
4. Recognize that this sequence pairs with a complementary sequence on the 16S rRNA component of the small ribosomal subunit, facilitating ribosome binding.
5. Conclude that the Shine–Dalgarno sequence functions as a ribosomal binding site in bacterial mRNA that helps initiate translation, distinguishing it from promoter elements, tRNA regions, or transcription termination signals.