Chromosomal localization of zebrafish AluI repeats by primed in situ (PRINS) labeling

Two zebrafish AluI repeats were localized in metaphase chromosomes by means of the primed in situ (PRINS) labeling technique, using oligonucleotide pr imers based on published sequences. An AT-rich, tandemly repeated, long Alu I restriction fragment (RFAL1) labeled the (peri)centromeric regions of all chromosomes. The GC-rich short fragment (RFAS) was found to be localized i n the paracentromeric regions of 17 chromosome pairs, which were mostly sub telocentric. The RFAS labeling pattern generally fits the previously descri bed chromomycin A(3) (CMA(3)) staining pattern. The differential compositio n of heterochromatin in zebrafish chromosomes is discussed.