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EXCEPTIONS. "This argument ignores systems like the bacterial XerD/C resolution machinery, which efficiently cuts dimeric circular chromosomes at specific dif sites. A similar system could have been used to resolve dimeric circles in the meiosis of early eukaryotes." https://lnkd.in/d8Qr_bk View in LinkedIn

SO ENDS this curated glimpse into gene life cycles. Pseudogenes, retrogenes, chimeric genes, gene recruitment and modification, gene silencing, and vertical gene transfer can occur at florid rates: there is nothing static in the world of genes. New metabolic pathways, new gene regulatory systems and genetic rewiring all occur continuously on biological timeframes, and all appear to be subject to, and shaped by, the great hand of natural selection by selective survival. View in LinkedIn

LINEAR PLUSES. "In the reductional division of meiosis, the homologous chromosomes are held together by their chiasmata where recombination has generated a crossover between homologous chromatids. A single meiotic crossover (or any uneven number of crossovers) generates a dicentric circle, which will lead to non-disjunction of the homologs. As this problem is circumvented with linear chromosomes, linearization may have provided a selective advantage." https://lnkd.in/d8Qr_bk View in LinkedIn

POTENT DRIVERS. "New genes now appear to be potent drivers of phenotypic evolution and the genetic control of important biological processes, and show that organismal development and organ development have evolved species-specific and lineage-specific components." https://lnkd.in/dvpUaYF View in LinkedIn

PLOIDY SWITCHES. "It was argued that switching between diploid and haploid states poses a problem for organisms with circular chromosomes." https://lnkd.in/d8Qr_bk View in LinkedIn

BECOMING ESSENTIAL. "Surprisingly, new genes can quickly acquire essential roles in development. Chen et al., identified 59 genes that originated in the last ~35 MYs in Drosophila that evolved essential developmental functions. Silencing new genes can also have a critical effect on reproduction, even when the individual can complete development." https://lnkd.in/dvpUaYF View in LinkedIn

SYNGAMIC FUSION. "The counterpart of meiosis, the syngamic fusion of haploid cells to form diploids may have been advantageous to survive famine as well as providing greater resistance to the highly mutagenic environment that existed 1 Gy ago." https://lnkd.in/d8Qr_bk View in LinkedIn

ANCIENT GENOME EDITING. "What were the disadvantages of circular chromosomes that could have ensured the supremacy of an incipient eukaryote with linear chromosomes? It has been suggested that the answer lies in the first division of meiosis. Meiosis may have first evolved as a mechanism to correct polyploidy arising from genome segregation mistakes." https://lnkd.in/d8Qr_bk View in LinkedIn

SUCCESSFUL CIRCULAR DESIGN. "Before the linear chromosomes of eukaryotes emerged ∼1 Gy ago, circular chromosomes had been successfully used for 2 Gy and they continue to predominate in the most common organisms on this planet (eubacteria and archaea)." https://lnkd.in/d8Qr_bk View in LinkedIn

WHY CIRCULAR CHROMOSOMES? "Meiosis entails chromosome segregation, and thus it is important to consider the nature of the chromosomes involved given that most modern prokaryotes have circular genomes." http://cshperspectives.cshlp.org/content/6/3/a016154.full View in LinkedIn