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UTILITY OF REDUNDANCY. “Increases in ploidy confer indubitable benefits: The resultant redundancy allows novel sequences/functions to arise in duplicate genes without compromising existing pathways, and recessive nonadaptive alleles, masked but carried through time, may prove to be adaptive in future contexts.” https://lnkd.in/ebVhXPf View in LinkedIn

ENGULFMENT. “An alternative possibility, leading to the same outcome, is that the earliest versions of cell–cell fusion entailed the engulfment of one protoeukaryote by another, with the internalized cell membrane then either digested or fused with the host cell membrane from within.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

PROVENANCE. “That Spo11 was present in the last eukaryotic common ancestor can be inferred by its presence in all of the major eukaryotic lineages studied thus far, with the notable exception of Dictyostelium discoidium and closely related slime molds that have apparently lost Spo11 but undergo complete meiotic sexual cycles.” https://lnkd.in/ebVhXPf View in LinkedIn

GENOME EXPANSION. “Cell–cell fusion generates an increase in chromosome number, and although the large size of modern eukaryotic genomes could also have been the consequence of endomitosis, it seems likely that cell–cell fusions contributed to genome expansion during protoeukaryote evolution.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

BOLT-ON. “Spo11 is derived from an ancestral archaeal topoisomerase VI homolog that became included in the protoeukaryote genome and was then adapted for meiosis. In essence, Spo11 is a topoisomerase that lost the ability to re-ligate DNA.” https://lnkd.in/ebVhXPf View in LinkedIn

PROK —> EUK: FOUR INNOVATIONS. “We propose that the transition to a sexual last eukaryotic common ancestor entailed four innovations: (1) alternation of ploidy via cell–cell fusion and meiosis; (2) mating-type regulation of cell–cell fusion via differentiation of complementary haploid gametes (isogametic and then anisogametic), a prelude to species-isolation mechanisms; (3) mating-type-regulated coupling of the diploid/meiotic state to the formation of adaptive diploid resting spores; and (4) mating-type-regulated transmission of organelle genomes.” https://lnkd.in/ebVhXPf View in LinkedIn

IMPORTED MACHINERY. “The enzymes and machinery for meiosis presumably evolved from a core set of DNA-manipulating enzymes brought in and modified as needed from prokaryotic forebears, including both bacterial and archaeal lineages which introduces the DNA double-strand breaks (DSBs) that provoke meiotic recombination.” https://lnkd.in/ebVhXPf View in LinkedIn

HIGH CERTAINTY. “During the course of this evolutionary trajectory, the last eukaryotic common ancestor became sexual, reassorting and recombining chromosomes in a process that entails regulated fusions of haploid gametes and diploid → haploid reductions via meiosis. That the last eukaryotic common ancestor was sexual is no longer a matter of speculation/debate as evidence of sex, and of genes exclusively involved in meiosis, has been found in all of the major eukaryotic radiations.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

PURGING. “Like parasexuality, meiosis also serves as a mechanism to purge deleterious mutations from the genome and also reveals recessive alleles in haploid progeny of a heterozygous diploid progenitor.” http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

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