DEVELOPMENT AND MAPPING OF POLYMORPHIC MICROSATELLITE MARKERS DERIVEDFROM A CHICKEN BRAIN CDNA LIBRARY

Until now the genetic linkage map in chicken has been based mainly on random genomic markers. The addition of expressed sequence tags (ESTs) to the genetic linkage maps is becoming more important because ESTs c an form the basis for comparative mapping studies. This may be helpful for the detection of candidate genes for quantitative trait loci (QTL s). In our study we used a (TG),, repeat as probe for the detection of microsatellites in a chicken brain cDNA library. After hybridization 0.15% of the cDNA clones gave a positive signal. The cDNA complexity o f the library was high; of the 90 cDNA clones that were sequenced 60 o ccurred only once. For 29 clones primer sets for the polymerase chain reaction could be developed, Twenty-one microsatellites were polymorph ic on one or more of the test panels and 15 markers could be mapped on either or both of the international reference families. Because seque nce homology between chicken and mammalian cDNAs is sometimes low it w as difficult to assess the level of sequence homology that indicated a true homologous transcript. In our study seven cDNA clones, of which three could be mapped, showed a relatively high percentage of sequence homology with sequences found in other species. Because sequencing an d mapping of expressed sequence tags in human and mouse is progressing very rapidly, it is predicted that further information will soon be r eadily available. Therefore, increasing the number of expressed sequen ces on the chicken genetic linkage map will be of value for comparativ e mapping studies in the near future.