3-6-13_germ cells and germ plasm

We summarized the essentiality relationship between

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Unformatted text preview: ). We summarized the essentiality relationship between parental gene–new gene pairs and found that the parental gene of a young essential gene can be either essential or nonessential, and vice versa (tables S10 and S11). These data suggested that a new essential gene can rise from either an essential or a nonessential parent (given that it represents the ancestral state of essentiality) and that either essential genes or nonessential genes can give rise to each type of gene. These processes appeared to be relatively independent (table S11, Fisher’s Exact test, two-tailed, P = 0.296). A previous case study of the sterile phenotype of a paternal-effect gene suggested that genes essential for fertility could arise in 10 My (26). Our observation of lethal phenotypes caused by the knockdown of young genes suggested that essential vital genes have been frequently generated in recent evolutionary periods. A new gene might not have become essential immediately after its origination. It, however, can integrate into a vital pathway by interacting with existing genes, and such interaction would be optimized Wolpert et al., 2e, Fig.This coevolution may by mutation and selection. 12.14 lead to the new gene becoming indispensable. This observation is supported by our modeling (8) with large-scale interaction data (27, 28), revealing genome-wide interactions of young essential genes with many previously unrelated genes (fig. S6). The mechanism for the evolution of essentiality would change with the types of new genes. A de novo gene has to evolve essentiality through neofunctionalization because it has no ancestral template. A duplicated gene, generated from an ancestral copy of its parental gene, could become Nance et al (2003). Development 130:5339-5350 Supporting Online Material www.sciencemag.org/cgi/content/full/330/6011/1682/DC1 Materials and Methods Figs. S1 to S8 Tables S1 to S11 References PIE-1 par genes are required for partitioning of germ plasm into the germ cell lineage 11 August 2010; accepted 1 November 2010 10.1126/science.1196380 cursors (P blastomeres) during the first embryonic divisions (Fig. 1A) (2). Like embryonic germ granules of other organisms, P granules have been hypothesized to harbor the determinants that specify the germlin...
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