Final answer:
Pre-mRNA splicing proceeds through a lariat structure formed by spliceosomes. The spliceosome recognizes the sequences at the ends of the intron and cuts the pre-mRNA, forming a lariat. The exons are then joined together to form a mature mRNA.
Step-by-step explanation:
The process of pre-mRNA splicing proceeds through a lariat structure formed by spliceosomes. Spliceosomes are protein complexes composed of small nuclear RNAs (snRNAs) and proteins. They recognize the sequences at the 5' and 3' ends of the intron and bind to them. The spliceosome then cuts the pre-mRNA transcript at these points, forming a lariat structure. The intron is released as the lariat is formed, and the exons are brought together and ligated, resulting in a continuous mature mRNA that is ready for translation.