Epigenetically imprinted genes at the Angelman locus. The region of 15q11-13 shown is approximately that of the most common 5-Mb deletion. On the paternal allele, the green genes are expressed but the red genes are not. On the maternal allele, the imprint is reversed, green genes expressed, and red genes are not. Genes shown in blue are active on both the paternal and maternal chromosomes. Colored arrows indicate the direction of active transcription. The 600-kb brain-specific UBE3A-ATS transcript (indicated by black arrow) silences the paternal copy of UBE3A. Deletion of the maternal region therefore results in loss of UBE3A expression in the brain.