mitosis & nuclear chromosome | conditional ts | maternal effect
Embryos from qrt mothers have abnormal nuclear spacing, abnormal numbers of centrosomes and abnormal chromatid separation.
Precellular embryos derived from homozygous females maintained at the restrictive temperature for 38-41 hours have unevenly spaced nuclei, which are often clustered in groups of two or four nuclei. Embryos also have abnormal amounts of DNA, abnormal numbers of centrosomes per nucleus, abnormal spindles, and abnormal chromosome separation during mitosis. DAPI-staining bridges between daughter nuclei are observed, suggesting that chromosomes are not separating completely at mitosis. The brains of larvae derived from homozygous females maintained at the restrictive temperature have a greatly reduced number of mitotic figures, with half of the mitotic figures having large, incompletely condensed chromosomes.
Biochemical defects in post-translational modifications lead to both reduced hatching rate and lethality during embryogenesis.
Homozygous adult females shifted to the restrictive temperature produce embryos with a drastically reduced hatching rate after 2-3 days at the restrictive temperature. This phenotype is reversible on returning to the permissive temperature.
temperature-sensitive
The relationship between the biochemical and developmental defects of qrt26 has been studied in temperature shift experiments. The level of unmodified proteins present increases in both ovaries of homozygous females and embryos derived from these females, the longer the females are kept at the restrictive temperature, until it is very high at 1-3 days. The presence of a high level of modified proteins correlates with maximal maternal lethality of the embryos.