Distribution of genomically unknown sequences (GUS) in the oral mucosa of three normal human volunteers. PCR primers were designed for each of eight GUS tags and performed on salivary DNA samples from three individuals (S1–S3). S1 was the individual from whom each GUS was originally identified. (B) is PCR performed on blood-derived DNA from subject 1; (C) is PCR performed on DNA derived from HEK293 cells. (NC) is a no-template DNA negative control. Universal bacterial 16S primers were used as positive control for the presence of bacterial DNA. Melanopsin (OPN4)-specific primers were used as positive control for the presence of human DNA. After sequence extension by vectorette-assisted genome walking, GUS 8 was identified as a human DNA sequence from clone RP11-318L16 on chromosome 1.
