What doctor should I go to, to take a genetic test to see if I may have cancer-causing genes in my genes?

Different options. A geneticist will help you go through your family tree assuming you know some details about the specific kinds of genetic disorders your other family members have, or you have. A medical oncologist is trained to perform a comprehensive evaluation to see if you have risk factors for having a particular genetic cancer syndrome, such as those that are related to breast and colorectal cancer.