Mosaicism in Turner's syndrome

Skuse et al. report that females with Turner's syndrome who have retained the paternal X chromosome (Xp) tend to achieve better cognition and social adjustment scores than those with the maternal X (Xm). As sex-chromosome mosaicism is frequent in Turner's syndrome, we argue that the presence of residual Y chromosomal sequences in the brain, which is exclusively possible in Xm Turner patients, might be a realistic alternative to the hypothesis of an imprinted X-linked locus as a reason for the behavioural differences between Xm and Xp Turner patients.