Aspects of nonrandom turnover involved in the concerted evolution of intergenic spacers within the ribosomal DNA of Drosophila melanogaster
- 1 August 1994
- journal article
- research article
- Published by Springer Nature in Journal of Molecular Evolution
- Vol. 39 (2), 151-159
- https://doi.org/10.1007/bf00163804
Abstract
Polymerase chain reaction (PCR)-amplified, sequenced, and digitally typed intergenic spacers (IGSs) of the ribosomal (r)DNA in D. melanogaster reveal unexpected features of the mechanisms of turnover involved with the concerted evolution of the gene family. Characterization of the structure of three isolated IGS length variants reveals breakage “hot spots” within the 330-base-pair (bp) subrepeat array found in the spacers. Internal mapping of variant repeats within the 240-bp subrepeat array using a novel digital DNA typing procedure (minisatellite variant repeat [MVR]-PCR) shows an unexpected pattern of clustering of variant repeats. Each 240-bp subrepeat array consists of essentially two halves with the repeats in each half identified by specific mutations. This bipartite structure, observed in a cloned IGS unit, in the majority of genomic DNA of laboratory and wild flies and in PCR-amplified products, has been widely homogenized yet is not predicted by a model of unequal crossing over with randomly placed recombination breakpoints. Furthermore, wild populations contain large numbers of length variants in contrast to uniformly shared length variants in laboratory stocks. High numbers of length variants coupled to the observation of a homogenized bipartite structure of the 240-bp subrepeat array suggest that the unit of turnover and homogenization is smaller than the IGS and might involve gene conversion. The use of PCR for the structural analysis of members of the rDNA gene family coupled to digital DNA typing provides powerful new inroads into the mechanisms of DNA turnover affecting the course of molecular evolution in this family.Keywords
This publication has 37 references indexed in Scilit:
- Evolution of genetic redundancy for advanced playersCurrent Opinion in Genetics & Development, 1993
- Secondary structure constraints on the evolution of Drosophila 28 S ribosomal RNA expansion segmentsJournal of Molecular Biology, 1991
- Nucleotide sequence of circular DNA molecules homologous to the 240 bp tandem repeats of the intergenic spacer of Drosophila melanogaster ribosomal DNABiology of the Cell, 1990
- Structure and evolution of the intergenic region in a ribosomal DNA repeat unit of wheatJournal of Molecular Biology, 1988
- Evolutionary divergence of promoters and spacers in the rDNA family of four Drosophila speciesJournal of Molecular Biology, 1987
- The silkmoth late chorion locusJournal of Molecular Biology, 1986
- Unequal exchanges and the coevolution of X and Y rDNA arrays in drosophila melanogasterCell, 1983
- Dynamics of concerted evolution of ribosomal DNA and histone gene families in the melanogaster species subgroup of DrosophilaJournal of Molecular Biology, 1982
- Long spacers among ribosomal genes of Drosophila melanogasterNature, 1980
- Evolution of Repeated DNA Sequences by Unequal CrossoverScience, 1976