 58 of these exons are constitutive and 4 exhibit alternative splicing ( 9a, 10a-2, 23a, and 28a).The genomic sequence starts 4,951-bp upstream of the transcription start site and 5,334-bp upstream of the translation initiation codon, with the length of the 5’ UTR being 484-bp long.There are three genes that are present within intron 27b of "NF1".