Correct! Sporadic cancer is caused by susceptibility gene variants and environmental exposures (exposure to chemicals, radiation), hormonal factors (levels of different hormones in the body), dietary habits, and other health behaviors.

Correct! Uncontrolled cell proliferation is one of the main hallmarks of cancer, and tumor cells have acquired damage to genes that are directly involved in regulating the cell cycle. Damage is caused by mutations producing an oncogene with a dominant gain of function, and/or by mutations in tumor suppressor genes causing a recessive loss of function. Regardless of the genetic damage or type of cancer, the common feature is a disrupted cell cycle.

Correct! Most cancers are caused by an accumulation of acquired mutations in somatic cells that happen mostly by chance and are not inherited. They are acquired sometime during a person’s lifetime. Sometimes these mutations are errors that occur during mitotic cell division. They can also be caused by things that damage a cell’s DNA, such as smoking, exposure to certain chemicals and radiation. The risk of sporadic mutations increases with age.

Correct! In the inherited form of retinoblastoma, mutations in the RB1 gene appear to be inherited in an autosomal dominant pattern. Autosomal dominant inheritance suggests that one copy of the altered gene in each cell is sufficient to increase cancer risk. A person with inherited retinoblastoma may inherit an altered copy of the gene (a germinal mutation) from one parent, or the altered gene may be the result of a de novo mutation that occurs in an oocyte or sperm cell or just after fertilization. For retinoblastoma to develop, a somatic mutation in the involving the other copy of the RB1 gene must occur in retinal cells during the person's lifetime. This second mutation usually occurs in childhood, typically leading to the development of retinoblastoma in both eyes.