Suppose nicole 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 nicole be at higher risk for getting breast cancer at an earlier age than her sister, tiffany, who inherited a normal brca1 allele from their mother?

Normal tumor suppressor gene controls excessive cell division

Explanation:

A normal tumor suppressor gene releases proteins that are essential to control and regulate the cell division. However, if this gene gets mutated then it may lead to uncontrolled cell division and hence forth cause cancer or tumor. Since Nicole got this mutant gene, hence her ability to suppress uncontrolled cell division does not work and hence she may get cancer as compared to her elder sister who received normal allele.