Final answer:
The statement is true; a lariat structure with a 5'-2' phosphodiester bond is formed during the splicing process of pre-mRNA, where the intron is removed and exons are joined.
Step-by-step explanation:
The statement "The lariat structure refers to the structure resulting from a 5'-2' phosphodiester bond involving the 5' end of the intron and an A in the intron that occurs during splicing" is true. During mRNA splicing, a lariat structure is formed when the branch point A residue within the intron forms a 5'-2' phosphodiester bond with the 5’ end of the intron. This branched lariat structure is an intermediate step in the splicing process carried out by the spliceosome, which eventually cuts out the intron and joins the exons together in a continuous mRNA sequence.