Month: September 2022

CARTOON PICTURE. "In evolutionary biology studies, meiosis is also often simplified and represented by random assortment of chromosomes and recombination maps expressing the probability of recombination events between ordered loci, with little attention to the molecular and cellular details." http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf View in LinkedIn

EVOLUTION OF MEIOSIS. "The origin of meiosis through gradual steps is among the most intriguing evolutionary enigmas." http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf View in LinkedIn

SINGLE EVOLUTIONARY EVENT. "Meiosis is one of the ‘major innovations’ of eukaryotic life that evolved before their subsequent radiation over one billion years ago. Extant eukaryotes share a set of genes specifically associated with meiosis, implying that meiosis evolved only once before their last common ancestor." (Brilliant review). http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf View in LinkedIn

EARLY EVENT. "A form of reductional cell division (a.k.a ‘proto-meiosis’) probably evolved in early asexual unicellular eukaryotes." https://lnkd.in/e2tp_G5 View in LinkedIn

SCENARIO 1. "Diploidy accidentally occurred by replication of the nuclear genome without subsequent cell division (“endoreplication”), and that returning to haploidy was selected for to correct this. Because either haploidy or higher ploidy levels may be favoured in different ecological situations, a variant of this scenario is that a proto-meiosis–endoreplication cycle evolved to switch between ploidy levels." https://lnkd.in/e2tp_G5 View in LinkedIn

SCENARIO 2. "Proto-meiosis evolved in response to the fusion of two haploid cells (“syngamy”), as in standard modern eukaryotic sexual life cycles. Syngamy may have been favoured because it allows recessive deleterious mutations to be masked in diploids." https://lnkd.in/e2tp_G5 View in LinkedIn

SCENARIO 2b. "In a variant of this scenario, early syngamy evolved as a result of ‘manipulation’ by selfish elements (plasmids, transposons) to promote their horizontal transmission." WOW. https://lnkd.in/e2tp_G5 View in LinkedIn

GENE CONVERSION. "During meiosis, crossover recombination results from the pairing of homologous chromosomes and the formation of DNA double-strand breaks (DSBs), followed by synapsis, a process in which homologues become tightly paired along their length involving a protein structure known as the synaptonemal complex. DSBs are then repaired as either crossovers (hereafter ‘COs’), resulting in the exchange of large chromatid segments, or gene-conversion events." http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf View in LinkedIn

UBIQUITOUS HOMOLOGOUS RECOMBINATION. "Most evidence suggests that homologous recombination evolved long before meiosis, as it occurs in all domains of life and involves proteins that share strong homology, but the origins and selective advantage of synapsis, gene conversion and recombination remain poorly understood." http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf View in LinkedIn

NUMBER 1: RETROTRANSPOSONS. "One hypothesis is that meiotic pairing and extensive homologous recombination in meiosis evolved to avoid the burden and consequences of non-allelic ectopic recombination in the large genomes of early eukaryotes, which have repetitive sequences. Such sequences might have been related to the spread of retrotransposons in early eukaryotes, of which many types are very ancient in eukaryotes but absent in bacteria and archaea." https://lnkd.in/e2tp_G5 View in LinkedIn