How to reference a region studied observation from genotype, haplotype, variant observations

I have a DR with multiple result (Observations). Each Observation could have different Region Studied. While I can add each Region Studied to the DR, this doesn't allow me to associate a specifc Genotype/Haplotype/Variant to a specific region studied. I'm looking for guidance how to do this. Observation.derivedFrom? I used to be able to use a component for "Description of ranges of DNA sequences examined".