Fig. 2

Identification of spr^tu21 as a mutation in cyclin B1 gene. (A) A partial genetic map of Linkage Group 5 showing microsatellite (z) markers used in mapping on the left; and the number of recombinants in relation to the total number of individuals on the right. Combined haploid and diploid data show the least number of recombinants between the specter allele and z58519 and z65883, an interval that includes 85 genes (Supplementary Table 1). (B) Chromatograph sequence data showing the C139T transition that results in a premature stop codon (red asterisk). (C) Exon structure of the cyclin B1gene product showing 9 exons (E1-E9) and putative protein coding regions: chromatin localization domain (CLD), destruction box (D-box), cytoplasmic retention domain (CRD), and Cdk1-binding domain. The spr^tu21 allele has a premature stop codon in exon 2 (red asterisk). (D-G′) cyclin B1 mRNA is (D, E) maternally, and (F, G) zygotically expressed. (F′-G′) Note that expression of cyclin B1 mRNA in the mutant embryo is significantly diminished at 10-somites (14 h) and absent by 15-somites (16.5 h).