The study of the pedigree has been carried out by man since ancient times. In the 18-19 centuries, the analysis of human pathology (incidence) began to be widely used. Thus, the genealogical method of research began to take shape . Subsequently, there was an improvement in both the line of compilation of pedigrees and the line of search for options for statistical analysis of available data.
The clinical-genealogical method is a method of researching pedigrees, the use of which allows us to trace the distribution of pathology in a family or family when specifying the type of kinship between their members.
This study option is considered universal. The genealogical method is used in solving theoretical problems quite widely. In particular, this research method is used for:
- establishing the character of the character of heredity;
- determining the type of inheritance of the disease or sign;
- assessment of penetrance (frequency of manifestation) of a gene;
- analysis of the mapping process (determining the position of the gene relative to others on the chromosome) and gene linkage;
- study of the intensity of the mutation process;
- deciphering the mechanisms on which gene interaction is based.
In modern medicine, a fairly large number of genetic pathologies are known. That is why a program has been developed to study each pregnant woman for six hereditary diseases. These include:
- phenylketonuria;
- Down syndrome;
- congenital hypothyroidism ;
- androgenital syndrome;
- galactosemia;
- cystic fibrosis.
The genealogical method may in some cases be the only way in which you can determine the type of inheritance of the disease in the family, find out the nature of the pathology, evaluate the prognosis of the disease, and make a differentiated diagnosis with other hereditary diseases. In addition, the use of this research option allows you to calculate the probability of birth of sick children, as well as to select appropriate and appropriate measures for antenatal diagnosis, prevention, treatment, adaptation and rehabilitation.
The genealogical method involves the compilation of a pedigree and its graphic image.
During these events, information is collected about the proband (the individual whose study the specialist is engaged in) and his family. As a rule, studies are conducted with the patient or the carrier of the studied trait. However, the genealogical method can be used not only in medicine.
In one parental pair, the children are called siblings (brothers and sisters). If there is only one parent - half siblings. They can be consanguineous (with a common father) or single-parent (with a common mother).
As a rule, a pedigree is drawn up to study several (or one) diseases (signs). The amount of information may depend on the number of generations involved in it (family tree).
The analysis of the information obtained involves the identification of a number of features when identifying types of inheritance.
For example, the autosomal dominant type is indicated by the frequent identification of the trait in the pedigree (in almost every generation), equally often in boys and girls. The presence of the trait in one of the parents contributes to its appearance in half or all of the offspring.
When compiling pedigrees, each generation should be located on its horizontal or radius. Generations are numbered in Roman, and family members in Arabic numerals.
If there are several hereditary diseases in the family that are not interconnected, the pedigree is compiled separately for each pathology.