Population-statistical method of research. What do genetics study in a population-statistical way?

The patterns of inheritance of various features inhuman organism is explored by the branch of biology - human genetics. It is closely connected with physiology, medicine, ecology and is designed to solve the problems of detection and early diagnosis of pathologies, the causes of which are aberrations in the gene pool of human populations - chromosomal, gene and genomic mutations. Population-statistical method is one of the most approved forms of detection and prognosis of syndromes - hereditary human diseases, this article will be devoted to its study.

Features of application of the method

Medical genetics in its work resorts tovarious forms of research on the human chromosome apparatus, drawing on the data of the exact sciences, statistics and clinical medicine. It is no accident that the theoretical basis of population genetics and its laws were formulated with the help of mathematical analysis. The population-statistical method is used not only to detect hereditary pathologies, but also to determine the frequency of occurrence of genes carrying these disorders, both in the homozygous recessive state and (more often) in a heterozygous phenotype not manifested.

The concept of a population

To establish the mathematical patternsdistribution of specific hereditary deposits in the gene pool, in genetics resort to the concept of the human population. What are the methods most in demand by modern science for studying it? Let's name three most important:

1. Population-statistical method.

2. The Genealogical.

3. The twin.

Genofond is understood as genotypes of all people,living in a given place. This may be the population of the whole country, a specific nationality or a human group that lives in isolation, for example, the inhabitants of a village lost in the mountains of Afghanistan or a tribe in the Amazonian jungle.

The genotypic characteristic of the population includesthe aggregate of all genes and external characters of its individuals. The population-statistical method of investigation is used to study both sporadic pathologies and those that have a clearly expressed genealogical form of manifestation.

The first group is the result of actionsituational teratogenic factors. Another group includes an extensive list of developmental anomalies that are systematically recorded in a particular family, nationality, or nationality for a sufficiently long period of time. For example, polydactyly, color blindness, hemophilia. To study the mechanism of transmission of pathological hereditary deposits that control these diseases, a population-statistical method is used.

Factors affecting the appearance of diseases with hereditary predisposition

A multifactorial nature has been proved by medicinegenetic, and environmental) pathologies that are manifested in a series of several human generations. Genetic analysis of hypertension, diabetes mellitus type I, bronchial asthma, schizophrenia and other diseases with hereditary predisposition requires the study of thousands of pedigrees.

In each casethe population-statistical method of genetics is able to reveal the level of reaction of the human group to the influence of environmental factors (radiation, microelement composition of drinking water, climate) and to establish how many genes it determines.

Are human diseases connected with genetic heterogeneity of the population?

What are the results of the comparative analysisdifferent ethnic groups living in the same external environment? The differing reaction of such populations to similar abiotic factors serves as evidence of their genetic heterogeneity.

Clinical, genealogical and populationstatistical method of studying human genetics have proved that the level of manifestation of pathology in families is comparable with its frequency in the population. They are used in the study of the genetic predisposition of rheumatism, allergy, as well as in clinical studies of the population affected by multifactorial diseases: multiple sclerosis, Alzheimer's disease, autism.

Mathematical justification of inheritance of characteristics

Before considering the features of geneticshuman populations, we will study its theoretical basis, presented in the form of a mathematical law. Its essence lies in the following: the genotype frequencies for any of the genes can be calculated using the square equation of the sum of two numbers. However, the population in question should be sufficiently numerous, it is impossible to drift genes and the forces of natural selection, and crosses occur spontaneously.

Applying the population-statistical methodstudy of human genetics and the results of clinical observations, it is possible to predict the frequency of phenotypic manifestation of defective genes and the probability of a child with pathology.

How to calculate the probability of manifestation of pathology

Here is an example of the inheritance of phenylketonuria -gene disease, which is based on a violation of the exchange of the essential amino acid phenylalanine. In populations of Europeans, the frequency of the pathological gene f is 1: 10,000, the patients are recessive homozygotes with the ff genotype.

Using the opportunitiespopulation-statistical method and mathematical calculations, it is possible to establish the frequency of the abnormal gene. It is equal to 0.01. Then the probability of the sign, expressed in the phenotype, will be 0.99. Hence, carriers of the recessive gene having the genotype Ff are 0.02. That is, in the considered population, approximately 2% of living people have in their genotype a recessive phenylketonuria gene.

As we see, the population-statistical method is used to calculate the frequency of the genes of the panmictic population responsible for the manifestation of hereditary pathologies.

Features of human populations

The evolution of the human civilization that formsbiological taxon, can be imagined as the development of individual communities, a long period of time living in similar conditions of the external environment. They include similar climatogeographic parameters, a single method of nutrition, common pathogens.

All this contributed to the consolidation in the gene poolpopulations of groups of normal allelic pairs of genes and in the early stages of anthropogenesis served as the basis for the action of hereditary varieties of variability and natural selection.

What do geneticists study in population-statisticalmethod at present? First of all, this effect on the human genome of forced isolation, closely related marriages, deterioration of the ecological situation. They led to burdening the gene pool of humanity with pathological genes and served as the reason for creating a wide network of medical and genetic consultations designed to detect a hereditary predisposition to the manifestation of various diseases.