genetic markers?

Question

when searching for the genetic basis of an illness, a good idea is to conduct a wide study of patients with that illness. How does one actually find a genetic marker, a gene with mutations that lead to a specific illness? What kind ofe xperimental design does that involve? (please be detailed)

Answer 1

When signifying genetic marker of a particular disease, the investigator should must study and identify a relationship with one of three things: the history of the illness and it tendency/association with other illnesses, the tendency of the illness to run within family lines.

Answer 2

Basically by computer pattern matching. Think of the dna patterns you see on TV when someone announces that two samples are so alike the odds are millions to one that they come from the same person.
To find a genetic marker, dna analysis is done on dozens or hundreds of patients and the output records are analyzed patterns which are the same or similar across many or all of them. If a common pattern is found, then humans must look and see it makes sense (it might mark hazel eyes when bone cancer is being checked) and look at the exceptions - those that don't have the bone cancer marker but definately have bone cancer might have worked in an industry with contamination problems, so it is not genetic.
Because of the cost and complications of the tests and the processing, typically the search will be done with a rather small but precise sample of patients and once a specific marker seems defined, examination of a larger sample while only computing comparisons near the marker would be done for confirmation.