title: Genome-wide characterization of Tetrahymena thermophila chromosome breakage sites. II. Physical and genetic mapping.
abstract: The chromosomes of the macronuclear (expressed) genome of Tetrahymena thermophila are generated by developmental fragmentation of the five micronuclear (germline) chromosomes. This fragmentation is site specific, directed by a conserved chromosome breakage sequence (Cbs element). An accompanying article in this issue reports the development of a successful scheme for the genome-wide cloning and identification of functional chromosome breakage sites. This article reports the physical and genetic characterization of 30 functional chromosome breakage junctions. Unique sequence tags and physical sizes were obtained for the pair of macronuclear chromosomes generated by fragmentation at each Cbs. Cbs-associated polymorphisms were used to genetically map 11 junctions to micronuclear linkage groups and macronuclear coassortment groups. Two pairs of junctions showed statistically significant similarity of the sequences flanking the Cbs, suggestive of relatively recent duplications of entire Cbs junctions during Tetrahymena genome evolution. Two macronuclear chromosomes that lose at least one end in an age-related manner were also identified. The whole-genome shotgun sequencing of the Tetrahymena macronucleus has recently been completed at The Institute for Genome Research (TIGR). By providing unique sequence from natural ends of macronuclear chromosomes, Cbs junctions will provide useful sequence tags for relating macro- and micronuclear genetic, physical, and whole-genome sequence maps.
authors.affiliation: Department of Microbiology and Immunology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Cassidy-Hanley
authors.forename: Yelena
authors.initials: Y
authors.lastname: Bisharyan
authors.forename: Vladimir
authors.initials: V
authors.lastname: Fridman
authors.forename: Joseph
authors.initials: J
authors.lastname: Gerber
authors.forename: Cindy
authors.initials: C
authors.lastname: Lin
authors.forename: Eduardo
authors.initials: E
authors.lastname: Orias
authors.forename: Judith D
authors.initials: JD
authors.lastname: Orias
authors.forename: Hilary
authors.initials: H
authors.lastname: Ryder
authors.forename: Linh
authors.initials: L
authors.lastname: Vong
authors.forename: Eileen P
authors.initials: EP
authors.lastname: Hamilton
mesh_terms: D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D016054:DNA, Protozoan; D017125:Genes, Protozoan; D008040:Genetic Linkage; D018503:Genome, Protozoan; D008540:Meiosis; D048631:Micronucleus, Germline / Q000502:physiology; D008969:Molecular Sequence Data; D020161:Physical Chromosome Mapping; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D016615:Telomere; D016808:Tetrahymena thermophila / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan