title: Unusually short tandem repeats in the chromosome end structure of Rhynchosciara (Diptera: Sciaridae).
abstract: The characterisation of chromosome end (terminal and sub-terminal) sequences of Rhynchosciara americana chromosomes was continued with the screening of a plasmid library made of amplified DNA fragments from a microdissected chromosome tip. An insert chosen for analysis hybridised to two chromosome ends and contains two microsatellite arrays in close vicinity to a sequence (named M-47), part of which is significantly similar to minisatellites of Salmonidae that are frequently present in the vicinity of microsatellite arrays. PCR results using a single primer representative of M-47 elements suggest that they are also repetitive in Rhynchosciara genomes. In addition, total single primer PCR products hybridised to the non-telocentric end subset of R. americana chromosomes. Another plasmid microlibrary made of chromosome tips amplified by a single M-47 primer was screened for repeats of Rhynchosciara chromosomes. Selected inserts that hybridised strongly to non-telocentric ends of R. americana and R. hollaenderi have a tandem array of 22 bp repeats (M-22). There is sequence divergence among M-22 repeats but their mean similarity is significantly high in relation to the M-22 consensus sequence derived from the cloned tandem array. M-22 elements lie distal to the 414 bp sub-telomeric satellite array characterised previously as suggested by double labelling for M-22 hybridisation and reverse transcriptase. M-47 elements, formerly identified in Salmonidae, thus contribute to specify unusually short repeats composing the sub-telomeric structure of two Rhynchosciara species.
authors: Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, Cidade Universitária, São Paulo, 05508-090, SP, Brazil.
authors: Renata M
authors: RM
authors: Rossato
authors: Christiane R G
authors: CR
authors: Madalena
authors: Eduardo
authors: E
authors: Gorab
mesh_terms: D000818:Animals; D001483:Base Sequence; D002875:Chromosomes; D004276:DNA, Satellite / Q000378:metabolism; D004175:Diptera / Q000235:genetics*; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA
chemical_list: D004276:DNA, Satellite