A 6p trisomy detected in a family with a "giant satellite".

A very large (giant) satellite was observed on one of the D-group chromosomes of a malformed and mentally retarded infant and her father. Detailed cytogenetic studies revealed that the giant satellite represented, in fact, a der(15) chromosome of translocation t(6;15)(p21;p12 or 13). The proposita was trisomic for a part of 6p(6pter leads to 6p21). The father was a balanced carrier, however, the deletion of the short arm of a No. 6 was hard to detect in routine karyotype analysis.