Suppose Alia recently learned that she inherited a mutant BRCA1 allele from her mother, who had breast cancer. BRCA1 is a tumor suppressor gene that is related to breast cancer. Why would Alia be at higher risk for getting breast cancer at an earlier age than her sister, Francine, who inherited a normal BRCA1 allele from their mother?

Due to the inheritance of a mutant tumor suppressor gene that will inhibit the regulation of cell proliferation and tumor development.

Explanation:

The normal BRCA1 allele is a tumor suppressor gene, that regulates cell division, DNA repair and apoptosis. Alia would be at a higher risk for getting breast cancer because she has inherited the mutant allele. When the normal tumor suppressor gene becomes mutated, the rate at which the cell proliferates will become uncontrollable, DNA repair will be unmanageable and apoptosis will be unachievable due to uncontrollable rate. Thus Alia inheriting this gene will predispose her to getting breast cancer at an earlier age if triggered coupled with some other factors.