Partial triplication and deletion of 13q: study of a family presenting with bilateral retinoblastomas.

This report compares the pathogenetic influences of selective deletion and triplicaton of chromosome 13 derived from a familial 12;13 insertional translocation. In the proband a heritable chromosomal basis for his bilateral retinoblastomas is established [46,XY,del (13) (pter leads to q12.5: :q22.1 leads to qter)mat], and in his sister the relatively modest effects of triplication of the mid-portions of 13q are demonstrated [46,XX,ins(12;13) (12pter leads to 12p11.2: :13q22.1 leads to 13q12.5: :12p11.2 leads to 12qter)mat]. Qualitative and quantitative gene marker studies and chromosomal staining techniques to differentiate timing of DNA replication failed to indicate functional gene changes about the breakpoints.