Multigene family of ribosomal DNA in Drosophila melanogaster reveals contrasting patterns of homogenization for IGS and ITS spacer regions: a possible mechanism to resolve this paradox

The multigene family of rDNA in Drosophila reveals high levels of within-species homogeneity and between-species diversity. This pattern of mutation distribution is known as concerted evolution and is considered to be due to a variety of genomic mechanisms of turnover (e.g., unequal crossing over an...

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Bibliographic Details
Published in:Genetics (Austin) 1998-05, Vol.149 (1), p.243-256
Main Authors: Polanco, C, Gonzalez, A.I, De la Fuente, A, Dover, G.A
Format: Article
Language:English
Subjects:
ADN
Animals
APAREAMIENTO CROMOSOMICO
APPARIEMENT CHROMOSOMIQUE
Base Sequence
CHROMOSOME
CHROMOSOME PAIRING
CHROMOSOMES
CLINES
Computer Simulation
CROMOSOMAS
DELETIONS
Deoxyribonucleic acid
DNA
DNA, Ribosomal - chemistry
DROSOPHILA MELANOGASTER
Drosophila melanogaster - genetics
Evolution, Molecular
FENOTIPOS
GENE
GENES
Genetics
GEOGRAPHICAL VARIATION
Insects
INTERGENIC DNA
INTERNAL TRANSCRIBED SPACER
LARGURA
LENGTH
LONGUEUR
MEIOSE
MEIOSIS
Meiosis - genetics
Models, Genetic
Molecular Sequence Data
MULTIGENE FAMILIES
Multigene Family
NEW SOUTH WALES
NOUVELLE GALLES DU SUD
Nucleic Acid Conformation
NUEVA GALES DEL SUR
PHENOTYPE
PHENOTYPES
Polymorphism, Genetic
QUEENSLAND
REPETITIVE DNA
RIBOSOMAS
RIBOSOME
RIBOSOMES
TASMANIA
TASMANIE
VICTORIA
X CHROMOSOME
Y CHROMOSOME
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Summary:The multigene family of rDNA in Drosophila reveals high levels of within-species homogeneity and between-species diversity. This pattern of mutation distribution is known as concerted evolution and is considered to be due to a variety of genomic mechanisms of turnover (e.g., unequal crossing over and gene conversion) that underpin the process of molecular drive. The dynamics of spread of mutant repeats through a gene family, and ultimately through a sexual population, depends on the differences in rates of turnover within and between chromosomes. Our extensive molecular analysis of the intergenic spacer (IGS) and internal transcribed spacer (ITS) spacer regions within repetitive rDNA units, drawn from the same individuals in 10 natural populations of Drosophila melanogaster collected along a latitudinal cline on the east coast of Australia, indicates a relatively fast rate of X-Y and X-X interchromosomal exchanges of IGS length variants in agreement with a multilineage model of homogenization. In contrast, an X chromosome-restricted 24-bp deletion in the ITS spacers is indicative of the absence of X-Y chromosome exchanges for this region that is part of the same repetitive rDNA units. Hence, a single lineage model of homogenization, coupled to drift and/or selection, seems to be responsible for ITS concerted evolution. A single-stranded exchange mechanism is proposed to resolve this paradox, based on the role of the IGS region in meiotic pairing between X and Y chromosomes in D. melanogaster.
ISSN:0016-6731
1943-2631
1943-2631
DOI:10.1093/genetics/149.1.243