DEVELOPMENT OF A GENETIC-MAP OF THE CHICKEN WITH MARKERS OF HIGH UTILITY

Microsatellites are tandem duplications with a simple motif of one to six bases as the repeat unit. Microsatellites provide an excellent opp ortunity for developing genetic markers of high utility because the nu mber of repeats is highly polymorphic, and the assay to score microsat ellite polymorphisms is quick and reliable because the procedure is ba sed on the polymerase chain reaction (PCR). We have identified 404 mic rosatellite-containing clones of which 219 were suitable as microsatel lite markers. Primers for 151 of these microsatellites were developed and used to detect polymorphisms in DNA samples extracted from the par ents of two reference populations and three resource populations. Sixt y, 39, 46, 49, and 61% of the microsatellites exhibited length polymor phisms in the East Lansing reference population, the Compton reference population, resource population No. 1 (developed to identify resistan ce genes to Marek's disease), resource population No. 2 (developed to identify genes involved in abdominal fat), and resource population No. 3 (developed to identify genes involved in production traits), respec tively. The 91 microsatellites that were polymorphic in the East Lansi ng reference population were genotyped and 86 genetic markers were eve ntually mapped. In addition, 11 new random amplified polymorphic DNA ( RAPD) markers and 24 new markers based on the chicken CR1 element were mapped. The addition of these markers increases the total number of m arkers on the East Lansing genetic map to 273, of which 243 markers ar e resolved into 32 linkage groups. The map coverage within linkage gro ups is 1,402 cM with an average spacing of 6.7 ch between loci. The ut ility of the genetic map is greatly enhanced by adding 86 microsatelli te markers. Based on our current map, -2,550 cM of the chicken genome is within 20 cM of at least one microsatellite marker.