Fig. 1: Ploidy reduction by mitomeiosis.
From: Induction of experimental cell division to generate cells with reduced chromosome ploidy
A schematic cell cycle and chromosome segregation mechanisms to daughter cells during canonical mitosis, meiosis I and meiosis II vs. mitomeiosis, an experimental reductive cell division induced in non-duplicated (2n2c) somatic cell genomes. Created in BioRender. Marti, N. (2025). a Chromosome dynamics and segregation during two consecutive meiotic cell divisions. Left panel shows the reductive meiosis I, where the duplicated homologous chromosomes consisting of sister chromatids pair, synapse and crossover followed by their segregation to the MII oocyte and its PB1. Right panel depicts the second meiotic division, where, similar to mitosis, sister chromatids segregate to the zygote and its PB2. b Left panel presents the canonical mitotic cell cycle, where following chromosome duplication, sister chromatids of each chromosome are segregated into two daughter cells maintaining the diploid chromosome content during cell divisions. Right panel demonstrates reductive mitomeiosis, where the nucleus at the G0/G1 stage is transferred into the cytoplasm of enucleated MII oocyte, thus bypassing the S-phase and prematurely entering the metaphase. The residual metaphase activity of enucleated MII-arrested oocyte forces premature condensation of non-duplicated chromosomes and formation of bipolar mitomeiosis spindle. Depending on chromosome positioning and attachment to the spindle, subsequent segregation of chromosomes to the zygote and the PB can result in either randomly reduced ploidy or haploidy in daughter cells.
