Possible localization of Gc-System on chromosome 4. Loss of long arm 4 material associated with father-child incompatibility within the Gc-System.

A mentally retarded girl with a sporadically occurring B/F translocation was reexamined with new banding techniques. Chromosome material from the long arm of chromosome 4 was inserted into the long arm of chromosome 20. The segment 4q11 leads to q13 was lost. The formerly reported abnormal segregation of the Gc-system was verified. The localization of the Gc-locus on the lost segment cannot be ruled out.