embryo & mitosis & nuclear chromosome
Homozygous γTub23CPI/γTub37C1 mutant females are agametic with rudimentary ovaries. The addition of γTub23C+tLa or γTub37C+t7.2 rescues these phenotypes. In homozygous γTub23CPI/γTub37C1 mutant embryos, germ cells form, migrate and populate the gonads as wild-type. Ovaries of mutant second instar larvae are also indistinguishable from wild-type. By the third instar larval stage the number of germ cells is slightly reduced. At prepupa stage, germ cells are found scattered throughout the mutant ovary, their total number is dramatically reduced. From this stage on germ cells degenerate and steadily disappear from the mutant, so that in adult ovaries the germaria are empty. In homozygous γTub23CPI/γTub37C1 mutant third instar larval females, half of the germ-line mitotic figures have centrosomes that are not aligned along the axis of the condensed chromosome plate. The condensation of the chromosomes is too high. Correspondingly, mitotic spindles are composed of shirt, often disorganised, microtubules associated with the chromosomes.