Alternative FGG pre-mRNA processing. The γA chain arises when polyadenylation occurs at polyadenylation signal 2 (pA2) downstream of exon 10 and all 9 introns are removed. The alternative γ′ chain arises after polyadenylation at pA1 in intron 9. This leads to the translation of a polypeptide with a unique 20-amino acid extension encoded by intron 9, substituting the 4 γA amino acids of exon 10.