Two healthy parents (asymptomatic) have a child with Tay-Sachs disease. Which of the following best explains this phenomenon and its possible screening?

Question

The phenomenon occurred because the parents are both carriers of the gene for the disease, but with screening of the parents combined with genetic counseling and embryo testing, the phenomenon could have dramatically been reduced.
The phenomenon occurred because both parents were gene carriers, but there is no testing available at this point for a disease such as Tay Sachs.
The phenomenon occurred because the dominant Tay-Sachs gene was active in the child, but not in the parents.
This phenomenon is not possible, since both parents are asymptomatic.
The phenomenon occurred due to a point mutation that occurred during fertilization, but testing could have informed the parents of the disease in their unborn child.

Answer 1

The phenomenon occurred because the parents are both carriers of the gene for the disease, but with screening of the parents combined with genetic counseling and embryo testing, the phenomenon could have dramatically been reduced.