It is happening now. A group of scientists are working on a project using mice. They interbreed the mice until they are all genetically the same in one diseaes trait, lets for example say obesity. They find the locus of the gene that is a marker for the triat and beed it pure, so that all mice born of that line are "fat'. They try to "knock out' the "fat gene" or do simple Mendelian genetics with breeding the fat mice with mice having other traits, to see how it is inherited.
It's all very complex , but the end result isn't. They to cross breed generations until the biomarker is changed or diluted. One day, we'll be told that the children of the union of two people will have a certain chance of developing serious diseases, based on the genetic profiling for diseases that are genetically based. Of course this has no bearing on environmentally caused diseases, but may be a step to stop the suffering of people who may inherit these diseases, based on genetic profiling. It's all so fascinating