Mammalian Chromosomal Evolution: From Ancestral States to Evolutionary Regions
Chromosome painting by fluorescence in situ hybridization (FISH) has allowed the detection of regions of orthology in most orders of mammals permitting the formulation of ancestral mammalian karyotypes at higher taxonomic levels. We show (1) how the avail
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Mammalian Chromosomal Evolution: From Ancestral States to Evolutionary Regions Terence J. Robinson and Aurora Ruiz-Herrera
Abstract Chromosome painting by fluorescence in situ hybridization (FISH) has allowed the detection of regions of orthology in most orders of mammals permitting the formulation of ancestral mammalian karyotypes at higher taxonomic levels. We show (1) how the availability of genome sequence data from outgroup species has facilitated the identification of chromosomes and chromosomal segments that define eutherian monophyly, and (2) that FISH together with in silico analysis of genomic sequences point to a nonrandom distribution of evolutionary breakpoints that are rich in repeat elements and segmental duplications. These regions may mediate rearrangement by nonallelic homologous recombination between misaligned copies of duplicated regions and lead to breakpoint reuse. Characters that have arisen convergently (i.e., homoplasy), pose a significant challenge in systematics, as does lineage sorting of genetic polymorphisms across successive speciation nodes (hemiplasy). We show how hemiplasy, a theoretically plausible evolutionary phenomenon, can materially affect data sets and explore the distinction between homoplasy and hemiplasy based on persistence times of phylogenetic markers.
T.J. Robinson Evolutionary Genomics Group, Department of Botany & Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa e-mail: [email protected] A. Ruiz-Herrera Unitat de Citologia i Histologia, Departament de Biologia Cellular, Fisiologia i Inmunologia, Universitat Auto`noma de Barcelona, Campus Bellaterra, 08193 Barcelona, Spain Institut de Biotecnologia i Biomedicina, Universitat Auto`noma de Barcelona, Campus Bellaterra, 08193 Barcelona, Spain e-mail: [email protected] This manuscript is a synthesis of spoken presentations by: Robinson TJ: Molecular discoveries at the root of the eutherian tree: Homoplasy, hemiplasy and ancestral states in the phylogenetic reconstructions of mammalian karyotypes. Ruiz-Herrera A: The genomic puzzle of mammalian evolutionary breakpoints: can we track any trend?
P. Pontarotti (ed.), Evolutionary Biology – Concepts, Molecular and Morphological Evolution, DOI 10.1007/978-3-642-12340-5_9, # Springer-Verlag Berlin Heidelberg 2010
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T.J. Robinson and A. Ruiz-Herrera
Introduction
Chromosome reorganization resulting from inversions, translocations, fusions, and fissions, among other structural changes, contributes to the shuffling of the mammalian genome and thus to the generation of new chromosomal forms on which natural selection may work. These rearrangements can be caused by the improper repair of double strand breaks (DSBs) and if the DNA damage occurs in the germ line and the structural rearrangements are transmissible, the modified chromosome(s) have the potential to establish in a population through selection and/or stochastic processes. It is this context that mammalian phylogenomics (the combination of genomics and phylogenetics
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