We observed 681 mosaic segments of size greater than 2 Mb on 641 autosomal chromosomes in 517 individuals for an overall frequency of individuals with mosaicism of 0.87% (Tables 1 and 2). The most frequent type of event observed was copy-neutral LOH (48.2%), while copy-gains and copy-losses were observed for 15.1% and 34.8% of mosaic events, respectively (Table 1). A small proportion (1.9%) of mosaic chromosomes were complex, harboring more than one type of event. 18.7% of mosaic chromosomal events spanned the entire chromosome, including 62 complete trisomies, predominantly in chromosomes 8, 12 and 15. 47.9% of mosaic chromosomal events began at a telomere and extended across some portion of the chromosomal arm (Table 1 and Figure 2). The majority of telomeric events were mosaic copy-neutral LOH (85.7%), most frequently on 9p (Table 3). The remaining mosaic chromosomal events were interstitial (31.5%) spanning neither telomere nor centromere, while an additional small proportion (1.8%) spanned the centromere or had more complex structure (e.g. distinct events involving both telomeres, but not the whole chromosome). The majority of interstitial events were mosaic copy-loss
