CHROMOSOMAL ANOMALIES ASSOCIATED

WITH RETINOBLASTOMA

1. 13q- Loss or mutation of an antioncogene located on the long arm of chromosome 13(13q14) is involved in the genesis of retinoblastoma.
   In familial cases of retinoblastoma, deletion or mutation of the Rb gene on chromosome 13 occurs in the germ cells of one parent. The resulting cell is nullisomic for the normal Rb gene and retinoblastoma develops.
2. A variety of cytogenetic abnormalities have been described in retinoblastomas of patients in whom the constitutional karyotype is normal. These include anticipated deletions of:
• Long arm of chromosome 13.
• Short arm of chromosome 1.
• Isochromosomes for 6p and 17q.