Question

why would someone with a mutation in the brca1 gene have a higher risk of developing cancer earlier in life than someone without a mutation in the brca1 gene?
it increases the chance that damaged dna will not be fixed.
a single mutation in dna usually causes cancer.
people with a mutated form of brca1 tend to engage in riskier behaviors.
it becomes more likely that additional nonhereditary mutations will occur.

Explanation:

The BRCA1 gene is involved in DNA repair. A mutation in BRCA1 impairs this repair function. Damaged DNA that is not fixed can lead to uncontrolled cell growth (cancer). A single DNA mutation usually doesn't cause cancer (many mutations are needed). There's no evidence that BRCA1 - mutated people have riskier behaviors. The key issue is the impaired DNA repair, not the likelihood of additional non - hereditary mutations (though that can be a consequence of impaired repair). So the main reason is that it increases the chance that damaged DNA will not be fixed.

Answer:

A. It increases the chance that damaged DNA will not be fixed.