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GrainGenes Reference Report: HER-86-522

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Reference	HER-86-522
Title	Physical locations of 5S and 18S-25S rDNA in Asian and American diploid Hordeum species with the I genome
Journal	Heredity
Year	2001
Volume	86
Pages	522-530
Author	Taketa S Ando H Takeda K von Bothmer R
Abstract	Summary: The physical locations of 5S and 18S-25S rDNA sequences in 15 diploid Hordeum species with the I genome were examined by double-target in situ hybridization with pTa7l (18S-25S rDNA) and pTa794 (5S rDNA) clones as probes. All the three Asian species had a species-specific rDNA pattern. In 12 American species studied, eight different rDNA types were found. The type reported previously in H. chilense (the 'chilense' type) was observed in eight American species. The chilense type had double 5S rDNA sites--two sites on one chromosome arm separated by a short distance--and two pairs of major 18S-25S rDNA sites on two pairs of satellite chromosomes. The other seven types found in American species were similar to the chilense type and could be derived from the chilense type through deletion, reduction or addition of a rDNA site. Intraspecific polymorphisms were observed in three American species. The overall similarity in rDNA patterns among American species indicates the close relationships between North and South American species and their derivation from a single ancestral source. The differences in the distribution patterns of 5S and 18S-25S rDNA between Asian and American species suggest differentiation between the I genomes of Asian and American species. The 5S and 18S-25S rDNA sites are useful chromosome markers for delimiting Asian species, but have limited value as a taxonomic character in American species. On the basis of rDNA patterns, karyotype evolution and phylogeny of the I-genome diploid species are discussed
External Databases	Pubmed: 11554968
Keyword	[ Hide all but 1 of 42 ] 18s-25s rdna 18s-5.8s-26s 5s 5s rdna addition american barley chromosome chromosome arm clone common wheat deletion differentiation evolution genome genus hordeum hordeum hybridization in situ in situ hybridization karyotype karyotype evolution loci marker multigene family organization pattern phylogeny physical location polymorphism probes rdna rdna sequence reduction relationships repetitive dna-sequences ribosomal rna genes satellite sequence site situ hybridization source

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