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UNIQUE FEATURE. "For this to succeed, mechanisms promoting sister chromatid cohesion were required. The unique feature of meiosis compared with mitosis is meiosis I in which chromosome homologs rather than sister chromatids segregate in a reductional division." https://lnkd.in/ebVhXPf View in LinkedIn

HALLMARK OF MEIOSIS. "A key innovation—indeed, the hallmark of meiosis—was synapsis between homologs." https://lnkd.in/ebVhXPf View in LinkedIn

SURVIVAL MECHANISM. "Notably, other types of DNA lesions, such as abasic sites or nicks generated by DNA deaminase acting to convert cytosine to uracil (a substrate for uracil N-glycosylase), can restore meiotic recombination in mutants of the fission yeast Schizosaccharomyces pombe lacking Spo11 (rec12) without generating double strand breaks." https://lnkd.in/ebVhXPf View in LinkedIn

COMPETITIVE ADVANTAGE. "Such a model is supported by the finding that the meiotic defects of S. cerevisiae spo11 mutants can be in part suppressed by gamma irradiation, suggesting that random double strand breaks can suffice to enhance meiotic crossovers and increase spore viability and germination." http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn

HYPOTHESIS. "Perhaps the most interesting hypothesis for why replication occurs before meiotic recombination in meiosis I is that in the pre-Spo11 era, the sister-chromatid copies served as the source of double strand breaks. Double strand breaks are formed by replication of nicked DNA, in which the nicks might have been incurred by UV or gamma rays before Spo11, and double strand breaks (but not nicks) are potent stimulators of homologous recombination." https://lnkd.in/ebVhXPf View in LinkedIn

"HERMAPHRODITIC AXES could have evolved through the simple restriction of B gene expression to part of a conelike structure, yielding both male and female organs on the same axis." https://lnkd.in/dVXk7jP View in LinkedIn

SPECIES INCOMPATIBILITY. "When different yeast species are induced to fuse with each other, their hybrid is unable to proceed smoothly through meiosis, even if all the chromosomes are colinear and syntenic, because a higher level of DNA mismatches provokes the mismatch repair machinery to abort meiotic recombination events, and spores fail to germinate." https://lnkd.in/ebVhXPf View in LinkedIn

TRANSITION ACROSS AXES. "One of the long-standing questions in seed plant evolution was how an ancestor with separate male and female reproductive axes (e.g., pinecones) made the transition to an angiosperm-like plant with hermaphroditic axes (flowers)." https://lnkd.in/dVXk7jP View in LinkedIn

SPECIES BARRIERS. "Modern sexual recognition systems are overwhelmingly prezygotic—cells recognize “self” via pheromones or cell-surface molecules that stimulate zygotic cell fusion—but postzygotic mechanisms have also evolved that permit cells to monitor how similar their chromosomal sequences are with respect to their fusion partner." https://lnkd.in/ebVhXPf View in LinkedIn

FRAGMENT FROM NATURE continues the curated contemplation on flower structure from last weekend. Flowers are an exemplar of many forms in nature, of how they evolved, and why. Being discrete and familiar, these lovely structures can open our minds to the complicated evolutionary paths that led to their current forms, not the least of it is the development of distinct sexes and mixed sex plants. Plants have among the most diverse and interesting types of reproductive strategies. Enjoy the tiptoe through the tulips for this last weekend. View in LinkedIn