Gene carrier detection in retinoblastoma.

Although the presence of the retinoblastoma (RB) gene is usually made obvious by bilateral RB tumors, unaffected relatives of RB patients and unilateral RB patients may also carry the gene. Patients with 13q14 deletion have RB, and segregation of RB with markers (Q-banding and Esterase D) on chromosome 13 can be studied in some two-generation RB families. Radiosensitivity of fibroblasts may be a marker or may be present only in chromosome 13 deletion patients. Growth properties of fibroblasts suggest that the RB gene itself is expressed in normal cells. Ultimately, gene-carrier detection may be achieved by defining gene expression, gene product, or by cloning the gene itself.