Homozygous Sld5^A462 mutants arrest at late embryo/first instar larval stage.

While wild-type mitotic figures appear normal, numerous types of mitotic defects are observed in wandering third instar larval brains of heterozygous Sld5^A462 mutants. All of the metaphase chromosomes observed in the heterozygous Sld5^A462 mutant background are characterised by defects in condensation as evidenced by longer than normal chromosomes. In addition, a variety of mitotic aberrations are observed including polycentric chromosomes, chromosome breakage, and telomere fusions. Mitotic index measurements for these tissues demonstrate significant M-phase delays in the mutant compared with wild-type. Larvae heterozygous for Sld5^A462 have S phase delays as compared to wild-type.