Question

Within introns, there is a conserved A nucleotide, called the branch point, which is important for the _______________ reaction.

Answer 1

The branch point A nucleotide within introns is important for the splicing reaction.

Step-by-step explanation:

Within introns, there is a conserved A nucleotide, called the branch point, which is important for the splicing reaction.

In both group-I introns and group-II introns, the branch point is crucial for the removal of introns and joining of exons.

In group-I introns, the branch point A nucleotide is important for the formation of a lariat structure.

This structure allows the 3'-hydroxyl group of the exon to attack the 3' end of the intron, resulting in splicing.

In group-II introns, the 2'-hydroxyl group of an adenylate residue within the intron attacks the 3' end of the exon, forming a branched lariat structure. This self-splicing mechanism does not require any external cofactor.