Characterization of a new repetitive sequence that is enriched on microchromosomes of turkey

We cloned and characterized a new highly repetitive, species-specific DNA sequence from turkey (Meleagris gallopavo). This repeat family, which accounts for approximately 5% of the turkey genome, consists of a 41 bp repeated element that is present in tandem arrays longer than 23 kb. In situ hybridization to turkey metaphase chromosomes (2n = 80) demonstrated that this sequence was located primarily on certain microchromosomes: approximately one-third of the 66 microchromosomes showed a positive signal. With respect to the macrochromosomes, hybridization was seen only in a pericentric position on nos. 2 and 3. The turkey microchromosome (TM) sequence shares motifs (alternating A3-5 and T3-5 clusters separated by 6-8 bp) that have been found previously in other avian tandemly repeated elements, e.g. a chicken microchromosomes sequence, and W (female) chromosome-specific sequences of chicken and turkey. However, the TM sequence does not cross-hybridize under moderately stringent conditions with these other sequences. The spread and amplification of related repetitive sequence elements on microchromosomes and W chromosomes is discussed.