Answer:
Pedigree analysis
Step-by-step explanation:
Pedigree analysis is a type of research used to study gene inheritance in humans. It is used to interpret genetic information or trait patterns displayed in a family tree. Pedigree analysis tries to analyze and determine the absence or the presence of a trait in relation to family members.
When a pedigree is done it shows the family history of a trait, hence can reveal, what chromosome the trait is linked to, family genotypes, dominant or recessive traits and phenotype probabilities in unborn children.
Therefore, from the question, the investigator is doing a type of hereditary research called pedigree analysis.