The genetic defects in Prader-Willi syndrome (PWS) and Angelman syndrome (AS) 
map to 15q11-13. Using microdissection, we have recently isolated several DNA 
probes for the critical region. Here we report that microclone MN7 detects 
multiple loci in 15q11-13 and 16p11.2. Eight yeast artificial chromosome (YAC) 
clones, two genomic phage clones, and two placenta cDNA clones were isolated to 
analyze these loci in detail. Two of the YAC clones map to 16p. Six YAC clones 
and two genomic phage clones contain a total of four or five different MN7 
copies, which are spread over a large distance within 15q11-13. One cDNA clone 
is from chromosome 15 and one is from chromosome 16. The chromosome 15 cDNA 
detects transcripts of 14 and 8 kilobases in various human tissues. The presence 
of multiple copies of the MN7 gene family in proximal 15q may conceivably be 
related to the instability of this region and thus to the etiology of associated 
disorders.