You can have genetic mutations that leave you more susceptible to getting cancer. But it’s the cells that mutate…for example, a keratinocyte, that if dividing haphazardly will develop into squamous cell carcinoma (a skin cancer). You can’t change your DNA but things like lifestyle modifications go a long way. For example just because someone has a gene for breast cancer, does not mean that they will get breast cancer.

Yup. Kinda. If you have two copies of the ccr5 delta 32 you can come into contact with hiv but it can’t get past the ccl5 and GP120 due to the mutation. Less protection with 1 copy. There’s still research on any negative impacts this mutation might cause.