45,X/46,XX mosaicism in discordant monozygotic twins.
Monozygotic twins discordant for Turner's syndrome were both mosaic for 45,X/46,XX in the blood with the same low frequency of 2% to 3% 45,X cells. However, the fibroblasts of the abnormal girl were all uniformly 45,X whereas her normal twin had only 46,XX cells. Monozygosity was confirmed by genetic markers, chromosome variants, and a single monochorionic placenta with a shared vascular circulation. The mechanism by which this disparate pair developed from a single zygote is suggested.
D003878:Dermatoglyphics; D004200:Diseases in Twins; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure; D005819:Genetic Markers; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008214:Lymphocytes / Q000648:ultrastructure; D009030:Mosaicism; D011247:Pregnancy; D014424:Turner Syndrome / Q000235:genetics*; D014430:Twins, Monozygotic
D005819:Genetic Markers