Maddie's father developed Huntington's disease; she is healthy but wants to be tested to see if she has the gene. What type of genetic testing will she have?

Maddie's father developed Huntington's disease; she is healthy but wants to be tested to see if she has the gene. What type of genetic testing will she have?

• A. Predictive genetic testing
• B. Diagnostic genetic testing
• C. Prenatal genetic testing
• D. Carrier genetic testing

Answer: (A)

The main idea here is testing someone who is at risk for a genetic disorder but has no symptoms yet. For Maddie, whose father has Huntington’s disease and who herself is healthy, the appropriate test type is predictive genetic testing. This is specifically used to determine whether an at‑risk, asymptomatic person carries the disease-causing mutation and will likely develop the condition in the future. Huntington’s disease is autosomal dominant and highly penetrant, so a positive result means a high probability of developing the disease, while a negative result reduces risk. Diagnostic testing, by contrast, is for someone who already has symptoms to confirm a current diagnosis. Prenatal testing is done during pregnancy to assess a fetus. Carrier testing is used for recessive disorders to see if someone carries one copy of a mutated gene; for Huntington’s, carriers would almost certainly develop the disease if they have the mutation, so carrier testing isn’t the relevant category here.

The main idea here is testing someone who is at risk for a genetic disorder but has no symptoms yet. For Maddie, whose father has Huntington’s disease and who herself is healthy, the appropriate test type is predictive genetic testing. This is specifically used to determine whether an at‑risk, asymptomatic person carries the disease-causing mutation and will likely develop the condition in the future. Huntington’s disease is autosomal dominant and highly penetrant, so a positive result means a high probability of developing the disease, while a negative result reduces risk.

Diagnostic testing, by contrast, is for someone who already has symptoms to confirm a current diagnosis. Prenatal testing is done during pregnancy to assess a fetus. Carrier testing is used for recessive disorders to see if someone carries one copy of a mutated gene; for Huntington’s, carriers would almost certainly develop the disease if they have the mutation, so carrier testing isn’t the relevant category here.