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Ribosomal DNA (rDNA) spacer polymorphism in mole rats
1National Institute of Genetics, Japan.
Molecular Biology and Evolution
|November 1, 1987
Summary
Genetic analysis of mole rat ribosomal DNA (rDNA) reveals distinct NTS polymorphism across chromosomal species. This variation suggests significant genetic divergence between mole rat karyotypes, with some populations showing evidence of gene flow.
Area of Science:
- Evolutionary genetics
- Molecular biology
- Mammalian genomics
Background:
- The Spalax ehrenbergi complex comprises four chromosomal species of subterranean mole rats in Israel.
- Ribosomal DNA (rDNA) nontranscribed spacer (NTS) regions are known for their variability and utility in population genetics.
Purpose of the Study:
- To investigate genetic differentiation using rDNA NTS polymorphism among the four chromosomal species of Spalax ehrenbergi.
- To determine if NTS polymorphism can distinguish between karyotypically distinct mole rat groups.
Main Methods:
- Analysis of rDNA NTS polymorphism in 50 individuals from 13 populations representing the four chromosomal species.
- Southern blot analysis using a mouse rDNA probe and restriction enzymes EcoRI and BamHI.
- Construction of restriction-site maps to confirm NTS length polymorphism.
Main Results:
- Southern blot analysis revealed significant variation in major restriction fragment sizes, attributed to NTS length polymorphism.
- Characteristic combinations of NTS types were identified for each chromosomal group, indicating genetic divergence.
- Populations near hybrid zones exhibited rDNA spectra similar to neighboring chromosomal groups, suggesting gene flow.
Conclusions:
- NTS rDNA polymorphism effectively differentiates the chromosomal species within the Spalax ehrenbergi complex.
- The observed genetic differentiation supports the distinct evolutionary trajectories of these mole rat karyotypes.
- Evidence of gene flow across hybrid zones highlights the dynamic nature of speciation in this complex.