TRANSLOCATION/NORMAL MOSAICISM IN D1 TRISOMY

A case of D 1 trisomy syndrome with classical facial appearance and central nervous system abnormalities is described in which the cytogenetic abnormality appeared to be a C-D translocation/normal mosaicism. Autoradiographic studies indicated that the DNA labeling pattern of the translocation chromosome was similar to that of the D 1 chromosome. Mosaicism of this type most likely results from chromatid arm interchange and subsequent segregation in the post-zygotic stage. Failure to find increased fetal hemoglobin in this instance may have been related to mosaicism or deletion effect.