The RB-1 gene has been identified as a tumor suppressor gene. The normal retinoblastoma gene product binds DNA and controls the cell cycle at the transition from the G1 to S phase.
Retinoblastoma arises when loss of function of both alleles of the gene in a retinoblast occurs.
In hereditary retinoblastoma, a chromosome containing the mutant form of the retinoblastoma gene is transmitted in typical autosomal dominant fashion. All of the cells of the body of a person who has inherited this mutation begin with only one normal copy of the retinoblastoma gene. When normal function in both alleles of a tumor suppressor gene is lost, cell division becomes uncontrolled leading to tumor growth. Tumors in hereditary retinoblastoma are often bilateral or multifocal and exhibit an earlier age of onset than sporadic retinoblastomas. Last updated Wednesday, February 21, 2001.