A 45,XX,21--child: attempt at a cytological and clinical interpretation of the karyotype.

Case Reports pericentric inversion and an unbalanced crossover segregation product from the inversion.However, the structurally abnormal chromosome involved is No. 4 and not a D chromosome. SummaryA non-satellited, slightly submetacentric chromo- some replacing one of the members of the 13-15 group was found in the apparently healthy father, paternal uncle, and sister; their karyotypes were otherwise normal.The aberrant chromosome is interpreted as being a result of pericentric inversion.One of the D chromosomes of the propositus was abnormally large and is assumed to represent duplication of a part of the long arm as a result of single crossover during meiosis in the father.