Project Director: John Colbourne

Microsatellite loci in Daphnia were isolated and characterized to provide hypervariable markers for constructing the genetic map and for localizing genes with significant phenotypic responses to environmental change by QTL analyses. They are also important molecular markers for population genetic study.

(click on image for microsatellite results)

Assuming a map length equal to that of Drosophila melanogaster, a randomly chosen gene is placed (on average) within 1 centiMorgan (cM) from the nearest marker (48.7% of loci within 0.1 cM) by mapping 1,000 microsatellites. Size-fractioned random DNA libraries, totaling 43,804 cloned fragments, were probed using short radiolabeled di- and tri-nucleotide repeats. From these, 2,366 positives were archived and 1,682 were sequenced from one end, averaging 700 bp reads. So far, the database contains 1,072 loci distributed among 764 DNA fragments. Because only 23% of the sequences span the whole vector-inserted DNA, the database will rapidly double by further sequencing the archived vectors from the other end. The microsatellite markers and their optimal reaction conditions are provided in a separate database. All markers are most likely conserved among members of the D. pulex species complex. However, over 60% of markers tested in cross-specific amplifications are possibly conserved within the subgenus Daphnia, whereas 48% and 18% are found to amplify Hyalodaphnia and Ctenodaphnia DNA. These markers are potentially valuable for population genetics and recombination mapping of distantly related species.

Download Microsatellite Markers. Excel format. Plain text format.

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