Splicing of pre-mRNA introns is accomplished by:
A) hydrolysis of two molecules of ATP.
B) hydrolysis of two molecules of GTP.
C) two transesterification reactions.
D) covalent attachment of guanosine to the 5'_end of the exon.
E) covalent attachment of the exon to the intron.

Question

Quizplus · Accepted Answer

Splicing of pre-mRNA introns is accomplished by two transesterification reactions. During the first reaction, the 2'OH group of an adenosine residue within the intron attacks the phosphate at the 5' end of the intron, resulting in the formation of a lariat structure and the release of the 5' exon. During the second reaction, the 3'OH group of the 5' exon attacks the phosphate at the 3' end of the 3' exon, resulting in the release of the intron and the joining of the two exons. No ATP, no GTP, no guanosine, and no covalent attachment of the exon to the intron are involved in the splicing mechanism.

Splicing of Pre-MRNA Introns Is Accomplished By