GENE-CENTROMERE DISTANCES IN TILAPIA

¹ Dept. of Zoology, University of New Hampshire, Durham, NH 03824 USA

² Institute of Aquaculture, University of Stirling, Scotland, FK9 4LA UK

To consolidate the genetic linkage map of tilapia (Oreochromis niloticus) we studied the segregation of microsatellite DNA loci in a family of meiotic gynogens. The fraction of heterozygous meiogynes provides information about the distance of a marker from its respective centromere. Of the 37 loci which were successfully amplified at the time of this writing, 3 were homozygous in all progeny . At the informative loci, recombination rates ranged from 3% to 100%, with a mean recombination rate of 48%. The distribution of recombination frequencies was distinctly bimodal, with 5 loci having recombination rates >90%, suggesting that interference may be reducing the frequency of double recombinants. Eighteen of the markers are found in 11 of the linkage groups previously generated from haploid individuals. Nine markers are within 25cM of their respective centromeres, and delineate 8 independent linkage groups.