Evidence that chromosome band 22q12 is concerned with cell proliferation in chronic myeloid leukaemia.

A man and two of his three children carried an abnormally short chromosome 22 resembling the Philadelphia chromosome (Ph1). Giemsa banding showed that the abnormal chromosome resulted from a translocation t(11;22) (q25;q13). The breakpoint on chromosome 22 was at the q12/q13 band interface compared with the breakpoint of Ph1 at the q11/q12 band interface. The absence of leukaemia or haematological disorder in members of this family suggests that the critical genetic site on chromosome 22 concerned with abnormal myeloid cell proliferation in human leukaemia is contained in the 22q12 band.