What is the primary function of small nucleolar RNAs (snoRNAs)?

Small nucleolar RNAs (snoRNAs) primarily function in the chemical modification of ribosomal RNA (rRNA). They guide the modification processes such as methylation and pseudouridylation, which are crucial for the maturation of rRNA molecules within the nucleolus before they become part of ribosomes. This process ensures that ribosomes are assembled with the correct structural integrity and functional capabilities necessary for protein synthesis. SnoRNAs play a significant role in the post-transcriptional processing of rRNA, which is essential for the proper functioning of the ribosomal machinery. Their activity directly impacts ribosome biogenesis, emphasizing their importance in cellular protein synthesis.

Other options, such as those related to mRNA synthesis, gene expression regulation, or DNA replication, do not accurately reflect the specific role of snoRNAs, which is distinctly tied to rRNA modification.