Figure 28.29. Splicing Mechanism Used for mRNA Precursors.

Figure 28.29Splicing Mechanism Used for mRNA Precursors

The upstream (5′) exon is shown in blue, the downstream (3′) exon in green, and the branch site in yellow. Y stands for a purine nucleotide, R for a pyrimidine nucleotide, and N for any nucleotide. The 5′ splice site is attacked by the 2′-OH group of the branch-site adenosine residue. The 3′ splice site is attacked by the newly formed 3′-OH group of the upstream exon. The exons are joined, and the intron is released in the form of a lariat. [After P. A. Sharp. Cell 2(1985):3980.]

From: Section 28.3, The Transcription Products of All Three Eukaryotic Polymerases Are Processed

Cover of Biochemistry
Biochemistry. 5th edition.
Berg JM, Tymoczko JL, Stryer L.
New York: W H Freeman; 2002.
Copyright © 2002, W. H. Freeman and Company.

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