Homozygous oocytes show defects in spindle morphology: microtubules often fail to be properly tapered at the spindle poles.
Eggs laid by mars1 and mars1/marsEP2477 flies show a greatly reduced ability to hatch. Sperm tails can be visualised in early-arrested embryos laid by mutant females, indicating that sterility is caused by arrest in embryogenesis after fertilization.
mars1 embryos, lacking maternal mars arrest during early embryogenesis after no more than five nuclear divisions. Approximately 82% of 15-45 minute old embryos laid by mars1 mothers exhibit at least two discrete DNA-containing regions, the first, localized to the embryonic cortext, resembling a polar body; and the second, surrounded by a bipolar spindle, is more central, indicating that the vast majority of mutant embryos pass though meiosis to form one or more mitotic figure.
The spindle structures in mars1 mutant embryos are very small and weak, albeit sill bipolar. Most exhibit at least one detached centrosome. Unaligned chromosomes are also found.
Embryos laid by mars1/marsEP2477 mothers resemble those from mars1 mothers, with less severe phenotypes.
mars1 heterozygous embryos appear wild-type and hatch normally.