A genetics question on indirect genetic analysis

[MudPhud20XX]

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So I've been reviewing Kaplan Medical Genetics and had a question like this:

Question: Indirect genetic analysis uses genetic markers closely linked to the disease locus to identify the presence of the disease. Which of the following is a major advantage of indirect genetics diagnosis?

The correct answer was: Multiple mutations can be assayed with a single test.

I chose "Disease-causing mutation can be followed."

The way I thought was that since you are using markers that can be linked to a mutation, you can follow the mutation, right? I get that there is always be an error due to recombination, but still I thought it would be the better answer.

Also, I don't think I understand how indirect genetic analysis helps detect multiple mutations in a single test. I mean can't direct genetic analysis do the same?

Can anyone help me out? Many thanks in advance.

 

[Renaissance Man]

Think of newborn genetic screening. These tests take blood from the baby and check to see if a multitude of mutations are present. If the mutation is there than the disease is probably also present (think genetic linkage). A tiny drop of blood from the babies heel can provide the results to multiple genetic defects at the same time as long as you have markers for said illness. Imagine you have fluorescent-tagged probe for GATA, and GATA is almost always linked to mutations in the PAH gene (PKU)...you could run this probe along with probes specific to a multitude of other genetic diseases at the same time.

From a practical reason, why would your answer choice be a major advantage? Why would you want to "follow the disease-causing mutation"? In my mind, you just want to see whether it is present or not, as this will guide treatment (again think newborn screening).

If I remember right, direct genetic analysis is looking for the specific cause of a genetic disease, not linked "markers" like in indirect genetic analysis. No idea if they can do multiple tests at same time for this, I would imagine these are more expensive though.