Human chromosome variation with two Robertsonian translocations.

A woman was found to have 42 autosomes due to engagement of both chromosomes 14 in Robertsonian rearrangements, one with a chromosome 21 and the other with a chromosome 22: t(14q21q) and t(14q22q). The two translocations appear monocentric and by silver staining have no rRNA activity. The t(14q21q) translocation is familial and was ascertained through a nephew with Down syndrome, while the origin of the t(14q22q) translocation was not established. In addition to these two translocations, the woman had XX/XXX sex chromosome mosaicism. She has had two recognized pregnancies, each resulting in the birth of a child with one of the two translocations. Both children are phenotypically normal, as is their mother, the first normal liveborn individual identified with two Robertsonian translocations.