Final answer:
The Shine-Dalgarno sequence is a 9-nucleotide sequence in prokaryotic mRNA that aids in the binding of mRNA to the small ribosomal subunit, initiating protein synthesis.
Step-by-step explanation:
The 9-nucleotide sequence in prokaryotic mRNA that facilitates binding to the small ribosomal subunit is the Shine-Dalgarno sequence. This sequence, typically found upstream of the start codon in prokaryotic organisms, is composed of the nucleotides AGGAGG and plays a critical role in initiating translation. The Shine-Dalgarno sequence aligns the mRNA with the 30S ribosomal subunit by interacting with the rRNA molecules within the subunit. This precise interaction is fundamental for the correct positioning of the mRNA for the initiation of protein synthesis.