Fig. 1. vls genomic region. (A) Four transcription units are found in a 12 kb stretch of DNA in region 38B (Butler et al., 2001). Df(2L)be408 uncovers CG10728, chk2 and a small region of the barr 5' end. Df(2L)pr2b deletes 38B1-2 to 38D2-E1. The fragments indicated as P[]were reintroduced by P-element-mediated transformation and recombined onto the Df(2L)pr2b or Df(2L)be408 chromosomes. chk2^null flies (Df(2L)be408, P[w⁺ CG10728⁺/vls⁺] / Df(2L)pr2b, P[w⁺ barren⁺]) are viable and fertile, demonstrating that chk2 does not have any essential function for development. E, EcoRI; B, BamHI; H, HindIII. (B) Magnification of the vls gene drawn to scale. Exons are shown as dark boxes, introns and untranslated regions (UTRs) as thin lines. The position of premature stop codons in the three vls^EMS alleles is indicated with the corresponding nucleotide substitution and codon change. The predicted 3' UTRs of vls and chk2 overlap over 127 bp. The asterisk indicates the N-terminal position of the polypeptide used for antibody production.