Behavior of aberrant chromosome configurations in Drosophila melanogaster female meiosis I.
Bottom Line: We show that these genotypes complete congression normally, with their chromosomes bioriented at metaphase I arrest at the same rates that they segregate, indicating that orientation must be established during prometaphase I before congression.We also show that monovalent chromosomes can move out on the prometaphase I spindle, but the dot 4 chromosomes appear required for this movement.Finally, we show that, similar to achiasmate chromosomes, heterologous chromosomes can be connected by chromatin threads, suggesting a mechanism for how heterochromatic homology establishes these unusual biorientation patterns.
Affiliation: Department of Biological Sciences, DePaul University, Chicago, Illinois 60614-3207 email@example.com.Show MeSH
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Mentions: We first examined females carrying monovalent compound chromosomes, which lack a homologous pairing partner entirely. In 2-d mated C(1)RM, y v/Ø; svspa-pol females, we found 56% of oocytes had chromosomes out on the prometaphase I spindle, with the unpaired C(1) chromosome out in 32% of oocytes (Table 1). The 4 chromosomes were found properly positioned on opposite sides of the spindle, and closer to the poles than the C(1) (Figure 1A, top). In aged virgins, we found 93% of oocytes with chromosomes in a single mass (Figure 1A, bottom). Of the exceptions, five were still in prometaphase with the 4s properly co-oriented (suggesting those oocytes had not yet completed congression), two had the major autosomes split into separate compact masses, and two were in a heterologous C(1)<=>44 configuration (2% HS). These cytological results are consistent with the rate of HS measured genetically in this stock (Table 1).
Affiliation: Department of Biological Sciences, DePaul University, Chicago, Illinois 60614-3207 firstname.lastname@example.org.