Article Abstract:
DNA polymorphisms in the ciliated protozoa Tetrahymena thermophila was identified using polymerase chain reaction-based randomly amplified polymorphic DNA (RAPD) with different primers. Some 30 RAPD polymorphisms were identified and obtained using a search targeted to a micronuclear locus called mat, which determines the mating type potentialities in the cell. A total of 10 RAPDs linked to either mat or Pmr were detected in the left arm of micronuclear chromosome 2. Testing of the mat-linked RAPDs using meiotic segregants identified the frequency of meiotic recombination to be 20 kb/cM. A generalized scheme of the main nuclear events and genomic exclusion crosses that were performed in the study is provided.
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Article Abstract:
The polymerase chain reaction (PCR) was used to amplify single-copy sequences within the Chelonia mydas genome for use in a global population genetic analysis of this endangered species. The use of PCR allowed the elimination of Southern hybridization in subsequent restriction fragment length polymorphism (RFLP) analyses. A total of 12 nuclear DNA polymorphisms were detected and used to characterize 15 nesting populations worldwide. The results showed a moderate degree of population substructure, which has both a biparental and a maternal component. Results also showed a strong association between geographic proximity and RFLP relatedness.
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Article Abstract:
Analysis of the population genetics implications of nearly neutral mutations was performed for a subdivided population structure with local extinction and recolonization. Results showed that the number of mutant substitutions decreased, while polymorphism increased, with increasing population size and a decreasing extinction-recolonization rate. Increasing the population size resulted in increased heterozygosity and decreased the substitution rate, but the balance between mutation and selection was not attained due to a migration effect. The model satisfactorily explained polymorphisms observed in Drosophila populations.
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