Microsatellites and Amplified fragment length polymorphism - Ecological world

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Thursday, 12 January 2017

Microsatellites and Amplified fragment length polymorphism



Microsatellites



         Microsatellites or simple sequence repeats (SSR) are hypervariable genomic regions characterized by short tandem repeat sequences of up to seven nu-cleotide units that are distributed throughout the genomes of most Eukaryotes (Powell et al. 1996). The variability of the number of repeat units at a par-ticuIar  locus and the conservation of the sequences flanking the repeat make microsatellites valuable genetic markers. They provide information for iden-tification and on genetic diversity and relationships among genotypes. For example, DNA fingerprinting with multilocus microsatellite probes suggested that Cape Town isolates of Arm illaria mellea s.s. were introduced from Europe more than 300 years ago (Coetzee et al. 2001). 


Amplified fragment length polymorphism (AFLP)




      AFLP is a powerful tool for DNA fingerprinting and is based on (1) total ge-nomic restriction, (2) ligation of primer adapters, and (3) unselective followed by selective PCR amplification of anonymous DNA fragments from the entire genome (Vos et al. 1995). AFLP markers are recognized as more reproducible compared to RAPD analyses and inter-simple sequence repeats (ISSRs), and are also able to give a higher resolution. AFLP analysis by Kauserud et al. (2004a) of European isolates of Serpula lacrymans belonging to five somatic incom-patibility groups indicated that the species in Europe is genetically extremely homogenous by observing that only five out of 308 scored AFLP fragments werepolymorphic. In contrast, S. himantioides as the closest relative to S. lacrymans possessed 31.3% polymorphic fragments.
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