Which event in the expression of the beta-hemoglobin gene is likely impaired by a mutation at the splice acceptor site?

A mutation at the splice acceptor site can significantly affect the splicing of pre-mRNA, which is crucial for producing a mature mRNA transcript. In eukaryotic cells, splicing is carried out by a complex of small nuclear ribonucleoproteins (snRNPs) and other proteins that recognize specific sequences at the splice sites.

The splice acceptor site is located at the 3' end of an intron and is essential for the correct removal of introns and the joining together of exons. If a mutation occurs at this site, it can disrupt the binding of the spliceosomal machinery necessary for correct splicing. This can lead to the inclusion of intronic sequences in the final mRNA or failure to splice out introns entirely, resulting in an aberrant mRNA that may not code for a functional protein.

Thus, the impairment in the splicing process directly relates to the interference with small nuclear ribonucleoproteins, which are responsible for recognizing and acting on the splice sites during the maturation of the beta-hemoglobin gene transcript.