Location of a euchromatic island flanked by centromeric satellite 3 repeats on the long arm of the Y chromosome. (A) Minimum tiling path for sequencing the Y chromosome as published by Tilford et al. (2001). (B) Enlarged view of the genomic region encompassing the centromere and satellite 3 repeats (Tilford et al. 2001). (C) Illustration of the P1-derived artifical chromosome (PAC) and bacterial artificial chromosome (BAC) clones assembled into the pericentromeric Yq11 contig. Blue lines indicate name and sequence length of respective clones. Clone names include library origin; accession nos. are in parentheses. PAC RP1-85D24 extends 2 kb into the satellite 3 sequence block forming a constant part of the human Y chromosome centromere (Tyler-Smith 1987). The overlap sizes of the clones are as follows: RP1-85D24 ↔ RP11-131M06 71,279 bp; RP11-131M06 ↔ RP11-886I11 33,248 bp; RP11-886I11 ↔ RP11-295P22 10,705 bp. RP11-295P22 overlaps by 10,417 bp with RP11-322K23, the most centromeric clone presented in Tilford et al. (2001). The distal half of RP11-295P22 consists exclusively of satellite 3 repeat sequence. Subtracting satellite 3 segments from the entire 554-kb sequence discloses previously unknown 450 kb of euchromatic DNA sequence.
