3.2. Genealogical method

Genealogical method is to study pedigrees organisms. This allows you to trace the nature of inheritance of different classes of certain features in a number of generations. It is widely used in medical genetics, breeding and more. With its help establish the genotype of individuals and calculate the probability of a particular manifestation of the signs of future generations.

Pedigrees are in the form of diagrams according to certain rules: the body females represent around, man - square. Designation of individuals of one generation are arranged in a row and interconnected by horizontal lines, and fathers and sons - vertical.

3.3. Population-statistical method

Population-statistical method enables you to study the frequency of occurrence of alleles in populations of organisms and genetic structure of populations. In population genetics, and it is used in medical genetics to study the distribution of alleles among certain people (mainly those that define certain hereditary diseases). This selective fraction of the population of a certain area and statistical process received data.

For example, using this technique, it was found that the allele that causes color blindness (color perception disorders), occurs in 13% of women (including disease only occurs in 0.5%) and 7% of men (all patients).

Population-statistical method allows to study the distribution of individual genes in populations of people. Usually made direct sample survey of population or study records of hospitals, maternity homes, and conducted surveys by questionnaire. The method you choose depends on the purpose of the study. The last phase is the statistical analysis.

One of the simplest and most versatile methods is the method proposed by G. Hardy and W. Weinberg (see Chap. II). There are a number of other special mathematical methods. As a result, we can determine the frequency of genes in different populations, the frequency of heterozygous carriers of a number of congenital abnormalities and diseases.

The study population may differ from biological features, geographical living conditions, economic conditions. Studying the prevalence of genes in specific areas shows that they can be divided into the following categories: 1) have a universal prevalence (includes most known genes) is recessive genes phenylketonuria and some other forms of mental retardation, occurring in the heterozygous state in I% of the population Europe colour blindness gene that manifests itself in 7% of men and 0.5% of women, but in the heterozygous state this gene have WITH% female, and 2) meet locally, mainly in certain areas, such as gene sickle-cell anemia, which is common in Africa and the Mediterranean; gene that causes congenital dislocation of the hip, has a high concentration of indigenous north-eastern part of Eurasia.

Population and statistical method to determine the genetic structure of populations (correlation between the frequency of homo-and heterozygotes). New possibilities for genetic analysis reveals the use of electronic computers. Knowledge of the genetic structure of populations of the population is of great importance for social hygiene and preventive medicine.