For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.

Explain why cancer is almost certain to develop with the inheritance of one mutated copy of RB1.

Key Concepts

Tumor Suppressor Genes

Tumor suppressor genes, such as RB1, are crucial for regulating cell growth and preventing uncontrolled cell division. When one copy of a tumor suppressor gene is mutated, the remaining normal copy can often compensate. However, in the case of retinoblastoma, inheriting one mutated RB1 gene significantly increases the risk of a second mutation occurring in the remaining normal copy, leading to cancer development.

Two-Hit Hypothesis

The two-hit hypothesis explains how cancer can develop in individuals with a hereditary predisposition. According to this model, the first 'hit' is the inherited mutation of one RB1 allele, which predisposes the individual to cancer. The second 'hit' occurs when the remaining normal allele is mutated, resulting in the loss of function of both alleles, which is necessary for tumor formation.

Dominant Inheritance

Dominant inheritance refers to the pattern where only one mutated copy of a gene is sufficient to increase the risk of a trait or disease. In the case of retinoblastoma, inheriting one mutated RB1 gene from a parent leads to a dominant predisposition to cancer, meaning that individuals are at a significantly higher risk of developing the disease, even if they do not exhibit symptoms initially.