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PROK TO EUK. “The transition from prokaryote to protoeukaryote to the last eukaryotic common ancestor (LECA) entailed conservation, modification, and reconfiguration of preexisting genetic circuits via mutation, horizontal gene transfer (HGT), endosymbiosis, and selection.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

WINNING UGLY. “An alternative view is that meiosis arose early, without prior parasexual experimentation, as a means to generate haploid progeny from a diploid progenitor. Early meiosis was likely messy and inaccurate—perhaps only somewhat better than parasexual changes in ploidy—with more accurate mechanisms evolving subsequently.” https://lnkd.in/ebVhXPf View in LinkedIn

MEIOSIS GENE REPERTOIRE. “Thus, like a V8 engine missing one spark plug, or a dog with three legs, the engine or animal can run but it is not pretty.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

MEIOSIS GENE. “The gene repertoire to complete meiosis is apparently more plastic than thought.” Spo11 ortholog. http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

PARASEXUAL RECOMBINATION. “In the C. albicans parasexual cycle, a low level of chromosomal recombination is detected in addition to chromosome loss and assortment, and these recombination events require the function of the C. albicans Spo11 ortholog, a central player in meiosis.” https://lnkd.in/ebVhXPf View in LinkedIn

VARIANT PARASEXUAL. “We also know about an unusual parasexual cycle that is extant in the most common human fungal pathogen, Candida albicans. In this species, mating occurs between diploids when the mating-type locus is homozygous (a/a and α/α) and the cells switch to a specialized mating cell type called opaque.” https://lnkd.in/ebVhXPf View in LinkedIn

ASPERGILLUS PARASEXUAL CYCLES. “More rapidly growing variants readily arise from homozygous diploids, but not from the corresponding haploid “parent,” and they are then reduced to a haploid state. The faster growing variants prove to harbor multiple recessive alleles, reciprocally epistatic, that together are beneficial but individually are deleterious, and thus they can only accumulate in the diploid and then be released during parasexual genome reduction. These studies illustrate the capacity of haploid-diploid-haploid parasexual cycles to generate genotypic and phenotypic diversity de novo.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

THE SHELTERED DIPLOID. “Aspergillus has a bona fide homothallic (selfing) sexual cycle, but also undergoes a parasexual cycle under laboratory conditions: Diploids are generated from haploid progenitors by hyphal fusion and the resulting diploid then loses chromosomes randomly to return to the haploid state. Recent studies have shown that this parasexual cycle provides access to a sheltered diploid state that can serve as a capacitor for evolution.” https://lnkd.in/ebVhXPf View in LinkedIn

TWO PHASES. “As one must walk before one can run, the fusion of cells may have led to early parasexual cycles from which true meiotic sexual cycles evolved at a later time.” https://lnkd.in/ebVhXPf View in LinkedIn

CUMBERSOME. “Increases in genome size/ploidy are expected to eventually become deleterious, however, one challenge being to organize a successful mitosis, another to regulate appropriate levels of gene expression. Hence, there would presumably have been positive selection for the acquisition of mechanisms to maintain copy number at a manageable size.” https://lnkd.in/ebVhXPf View in LinkedIn