A family with D-D translocation.

Balanced D/D translocation carriers appear to be normal in most instances (Court-Brown et al., 1966; Giannelli and Howlett, 1966). In some cases, however, a variety ofcongenital malformations has been reported, such as Klinefelter's syndrome (Lejeune, Turpin, and Decourt, 1960), little secondary sex development (Walker and Harris, 1962), malformation of the spine (de Grouchy et al., 1963), arrested hydrocephalus accompanied by mental retardation and spastic diplegia (Jagiello, 1963), and hydrocele and azoospermia (Yunis et al., 1964). Dekaban (1966) described a family with transmission of a D/D translocation and a high incidence of mental retardation. A D/D translocation was found in a patient with Down's syndrome; in that case, the patient had a modal number of 46 and a trisomy 21 (Zergollern et al., 1964). It has also been suggested as a cause of familial non-disjunction (Hamerton, Giannelli, and Carter, 1963), and was found in association with chronic granulocytic leukaemia (Engel et al., 1965). When appearance and measurements of the D group chromosomes were used as criteria for identifying the chromosomes involved in reciprocal translocation, chromosomes 13 and 15 (Walker and Harris, 1962; Hamerton et al., 1963), and 14 and 15 (Lejeune et al., 1960; de Grouchy et al., 1963; Zergollem et al., 1964) were suggested as the chromosomes of origin. Using 3H-thymidine labelling and autoradiography, Yunis et al. (1964), Giannelli and Howlett (1966), Dekaban (1966), and Tiepolo et al. (1967) assumed that the chromosomes involved in reciprocal translocation were a late and an intermediate replicator, probably Nos. 13 and 14. ' The purpose of this paper is to describe a family in which a D/D translocation chromosome was