Imprinted cluster on mouse chromosome 7C. Upper and lower boxes represent genes expressed from the paternal and maternal alleles respectively. Small nucleolar RNAs (snoRNAs) MBII-13, MBII-85 and MBII-52 genes lie within introns of long primary transcripts initiated at the U exons (U9 to U1 exons). Arrows indicate the transcriptional orientation of the genes. Frat3, Mkrn3, Magel2 and Ndn lie within 120 kb and around 1.5 to 2 Mb from the Snurf-Snrpn gene. Location of BAC109 used for the transgenic study is represented.