The murine vav locus and DNase I hypersensitive sites. Cloned genomic sequences are shown as a solid line, with the relevant phage clones above. An uncloned gap of approximately 5 kb lies between λ7.2 and λ20.1. Approximate positions of exons (shown as boxes) were assigned by Southern blotting of enzyme-restricted phage clones using cDNA fragments as probes; only the first and second of at least 14 exons are numbered. The major DNase I hypersensitive sites are indicated by large triangles and minor, inconsistent sites are indicated by small triangles. The expanded map shows the positions of the five major HS sites in more detail, with the 5′ UTR of exon 1 depicted as an open box and the coding region filled. The bar below indicates the sequenced proximal promoter region (see text). Abbreviations: A, Ava I; B, BamHI; Bg, Bgl II; Hp, Hpa I; H, HindIII; K, Kpn I; N, NcoI; Ne, Nae I; R, EcoRI; S, Sac I; X,Xba I. Not all sites for these enzymes are shown.