Fig. 1. Genomic and molecular analysis of myt1. (A) An alignment of Myt1 sequences from Xenopus laevis, Homo sapiens and Drosophila melanogaster. Black shading indicates identical amino acids and gray shading highlights similar amino acids. The Myt1 protein sequence contains a kinase domain (purple bar), a potential trans-membrane domain (green bar) and a predicted C-terminal Cyclin B interaction motif (brown bar). (B) Physical and genetic map of myt1 and flanking genes uncovered by Df(3L)64D-F (white box). Black triangles indicate the position of the nearest lethal P-element insertions that complement Df(3L)64D-F. The black bar showing restriction enzyme sites (RI, EcoRI; SI, SalI) represents a 24 kb DNA sequence (coordinates 240,000 to 264,000) in AE003565, a genomic BAC clone. The narrow black bar represents the DNA fragment that was subcloned to generate P{myt1⁺}. Black arrow bars represent transcripts of myt1⁺ and the nearest flanking genes. Roman numerals indicate exons I to IV of the myt1 gene. (C) A single base deletion mutation in myt1¹ (and myt1²) beginning at amino acid position 173 causes a frame-shift, producing an altered amino acid sequence in Myt1 (red letters) that ends with a premature stop codon at position 231.