Genealogical method

Medical Genealogy (from Greek: γενεαλογία genealogia from γενεά genea, "generation" and λόγος logos, "knowledge"), is the study of families, family lineages and medical family history. Information about a family is obtained by oral interviews (e.g. by a clinical geneticist, any other physician or a genetic couselor), from medical and historical records, (previous) genetic analysis, and others. The results are displayed and kinship of members of the family are commonly demonstrated in pedigrees or rarely written as narratives. G. serves in basic research of genetic rules in transmission of a trait and, in clinical (medical) genetics, for clinical consulting practice at follow-up of inheritance of various traits.

Pedigree
This is a graphical recording of kinship relations between persons in individual generations. It represents the foundation of genealogical method and bring/provide basic informaion about the occurrence of chosen trait/phenotype. In the drawing up of a pedigree standard symbols and lines are used (see figures below). More detailed information about the family members is indicated in the legenda (e.g. under or beside the pedigree). The legenda refers to individual members of family through coordinates – generations are numbered by Roman and individuals in a generation by Arabic numerals.

Proband
The person providing the information for construction of pedigree and being interested in evaluation/estimate of the probability (risk) of recurrence of the trait; in the pedigree, this person is labeled with arrow.

Genealogy analysis as a method of research
From biological point of view, genealogy. is considered as one of methods of genetic research. It resides in a selection of families with suitable type of crossing. Afterwards, this genealogy material is subject of logical analysis. In individual families, the effort is made to explain the transmission of traits by schedules used in experimental phenogenetics. For examination of the type of genetic determination in genealogy, many statistical methods (and now computer programs) have been developped enabling investigate the ratios, the penetrance of followed gene, and estimate the heritability using a collection (date-base) of pedigrees.