Medical Genetics pedigree They are graphic representations of a family tree which show the biological relationship of the index case or proband or propositus to the est of the individuals A family tree diagram that shows how a particular genetic trait or disease has been inheritedMedical Genetics pedigree They are graphic representations of a family tree which show the biological relationship of the index case, or proband or propositus to the rest of the individuals. A family tree diagram that shows how a particular genetic trait or disease has been inherited