title: Chromosome segment duplications in Neurospora crassa: barren crosses beget fertile science.
abstract: Studies on Neurospora chromosome segment duplications (Dps) performed since the publication of Perkins's comprehensive review in 1997 form the focus of this article. We present a brief summary of Perkins's seminal work on chromosome rearrangements, specifically, the identification of insertional and quasiterminal translocations that can segregate Dp progeny when crossed with normal sequence strains (i.e., T x N). We describe the genome defense process called meiotic silencing by unpaired DNA that renders Dp-heterozygous crosses (i.e., Dp x N) barren, which provides a basis for identifying Dps, and discuss whether other processes also might contribute to the barren phenotype of Dp x N and Dp x Dp crosses. We then turn to studies suggesting that large Dps (i.e., >300 kbp) can allow smaller gene-sized duplications to escape another genome defense process called repeat-induced point mutation (RIP), possibly by titration of the RIP machinery. Finally, we assess whether in natural populations dominant RIP suppressor Dps provide an "RIP-free" niche for evolution of new genes following the duplication of existing genes.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Parmit K
authors.initials: PK
authors.lastname: Singh
authors.forename: Srividhya V
authors.initials: SV
authors.lastname: Iyer
authors.forename: Mukund
authors.initials: M
authors.lastname: Ramakrishnan
authors.forename: Durgadas P
authors.initials: DP
authors.lastname: Kasbekar
mesh_terms: D015825:Chromosomes, Fungal / Q000235:genetics*; D003433:Crosses, Genetic; D020440:Gene Duplication; D006579:Heterozygote; D008540:Meiosis; D009492:Neurospora crassa / Q000235:genetics*; D010641:Phenotype