Month: September 2022

THE EXCEPTIONS. "On the other hand, very few examples can be found where genome sequencing has led us to infer a strictly asexual nature of the respective eukaryote." https://lnkd.in/deZ8DED View in LinkedIn

EUKS AND MEIOSIS. "In summary, long-term asexuality is rare, and there is growing consensus that meiotic sex was present in the LECA and remains so in all major eukaryotic lineages." (LECA = last eukaryotic common ancestor), https://lnkd.in/deZ8DED View in LinkedIn

GENES, CELLS, AND NUCLEI. "In the excitement over the recognition of meiosis-associated genes all over the eukaryotic phylogenetic tree, one might forget that fusion of both cells and nuclei is also critical during the sexual cycle. However, gamete fusion (plasmogamy) and nuclear fusion (karyogamy) have been studied much less than meiosis." https://lnkd.in/deZ8DED View in LinkedIn

CASE STUDY. "If we accept the view that any costly nonadvantageous mechanism is subject to eventual loss, sex retention proves its usefulness, and bdelloid rotifers and ciliates, possibly having done without sex over an extended time period, might enlighten us regarding that use." https://lnkd.in/deZ8DED View in LinkedIn

ROTIFERS AND CILIATES. "Although meiotic sex was lost in a few multicellular lineages millions of years ago, they constitute rare exceptions. These lineages represent easily amenable multicellular systems, and population genetic analysis showed that they do not suffer from the lack of genetic diversity, which is retained among different clones." https://lnkd.in/deZ8DED View in LinkedIn

SEX IN EMERGENCIES. "It has also been pointed out that for a single cell the costs of meiosis are high due to the time and effort it has to invest and that, in protists, sexual reproduction is often associated with their survival of harsh periods." https://lnkd.in/deZ8DED View in LinkedIn

CLONAL UNDER STEADY STATE. "Under more constant optimal conditions, relatively simple organisms with short generation times are selected for high numbers of progeny, which can most efficiently be achieved by asexual reproduction. Thus, clonal reproduction may last for an extended period. However, when adverse conditions or internal constraints are encountered, sex is induced." https://lnkd.in/deZ8DED View in LinkedIn

TWO WORLDS. "Thus, despite the presence of organisms with long periods of clonality and occasional instances of aneuploidy and parasexuality, which deviate from regular standard meiotic sex, its option is still overwhelmingly present in practically all eukaryotes." https://lnkd.in/deZ8DED View in LinkedIn

LESSONS LARNED. "The bdelloid rotifers have more to tell us. Genomic analysis shows gene conversion, limiting the accumulation of mutations in absence of meiosis. Genes defending against transposons are increased, correlating with the fact that transposable elements make up only 3% of the genome. Horizontal gene transfer is very abundant, with 8% of the genes most likely acquired in this fashion. In this respect, bdelloids seem to have “returned” to the prokaryotic form of sex." https://lnkd.in/deZ8DED View in LinkedIn

OXIDATIVE DAMAGE THEORY. "Did Meiotic Sex Evolve in Response to Reactive Oxygen Species? Lately, more and more research has uncovered links between stress conditions, such as Reactive Oxygen Species formation, and meiotic sex. One essential question of course remains: where did the Reactive Oxygen Species that possibly gave rise to the invention of meiotic sex in eukaryotes come from?" https://lnkd.in/deZ8DED View in LinkedIn