Patterns of inheritance of various characters inthe human body explores a branch of biology - human genetics. It is closely related to physiology, medicine, ecology and is designed to solve the problems of identifying and early diagnosis of pathologies caused by aberrations in the gene pool of human populations - chromosomal, gene and genomic mutations. The population-statistical method is one of the most approved forms of detection and prognosis of syndromes - hereditary human diseases, and this article will be devoted to its study.
Features of the method
Medical genetics in their work resorts tovarious forms of research on the human chromosomal apparatus, involving data from the exact sciences, statistics and clinical medicine. It is not by chance that the theoretical basis of population genetics and its laws were formulated using mathematical analysis. The population-statistical method is used not only to identify hereditary pathologies, but also to determine the frequency of occurrence of genes carrying these disorders, both in a homozygous recessive state and (more common) in a heterozygous, non-manifested phenotypic form.
Population concept
To establish mathematical patternsdistribution of specific hereditary inclinations in the gene pool, in genetics resorted to the concept of the human population. What methods are most in demand by modern science to study it? Let's name three major:
1. Population-statistical method.
2. Genealogical.
3. Twin.
Под генофондом понимают генотипы всех людей, living in a given place. This may be the population of an entire country, a specific nationality or a human group that lives in rather isolated ways, for example, residents of a village lost in the mountains of Afghanistan or a tribe in the Amazonian jungle.
The genotypic characteristics of the population includeset of all genes and external signs of its individuals. The population-statistical research method is used to study both sporadic pathologies and those that have a clearly defined genealogical form of manifestation.
The first group arises from the actionsituational teratogenic factors. Another group includes an extensive list of developmental anomalies that are systematically recorded in a particular family, nationality, and nationality over a sufficiently long period of time. For example, polydactyly, daltonism, hemophilia. To study the transmission mechanism of the pathological hereditary inclinations controlling these diseases, the population-statistical method is used.
Factors affecting the emergence of diseases with hereditary predisposition
Medicine has proven multifactorial nature (asgenetic and environmental pathologies that manifest themselves in a series of several human generations. Genetic analysis of hypertension, type I diabetes, 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 identify the level of the human group's reaction to the effects of environmental factors (radiation, microelement composition of drinking water, climate) and to determine how many genes it is determined by.
Are human diseases related to genetic population heterogeneity?
What are the results of a comparative analysis?different ethnic groups living in the same external conditions? The differing reaction of such populations to similar abiotic factors is evidence of their genetic heterogeneity.
Clinical, genealogical and populationA statistical method of studying human genetics has shown that the level of manifestation of pathology in families is comparable to its frequency of occurrence in a population. They are used in the study of genetic susceptibility of rheumatism, allergies, as well as in clinical studies of the population affected by multifactorial diseases: multiple sclerosis, Alzheimer's disease, autism.
Mathematical justification for the inheritance of traits
Before considering the features of geneticshuman populations, we study its theoretical basis, presented in the form of a mathematical law. Its essence is as follows: the frequency of genotypes for any of the genes can be calculated using the equation of the square of the sum of two numbers. However, the population under consideration should be quite numerous, gene drift and the action of the forces of natural selection are impossible in it, and crossing occurs spontaneously.
Using the population-statistical methodstudying human genetics and the results of clinical observations, it is possible to predict the frequency of phenotypic manifestations of defective genes and the likelihood of having a child with pathology.
How to calculate the probability of manifestation of pathology
Let us give an example of the inheritance of phenylketonuria -gene disease, based on metabolic irreplaceable amino acid phenylalanine. In populations of Europeans, the frequency of occurrence of the pathological gene f is 1: 10,000, patients are recessive homozygotes with the ff genotype.
Using opportunitiespopulation statistical method and mathematical calculations, you can set the frequency of the anomalous gene. It is 0.01. Then the probability of the trait expressed in the phenotype will be 0.99. Hence, carriers of the recessive gene with the Ff genotype are 0.02. That is, in the population under consideration, about 2% of the living people have a recessive phenylketonuria gene in their genotype.
As we see, the population-statistical method is used to calculate the frequency of genes of the panmictic population responsible for the manifestation of hereditary pathologies.
Peculiarities of human populations
The evolution of human civilization forminga biological taxon can be represented as the development of individual communities, a long period of time living in similar environmental conditions. They include similar climatogeographical parameters, a single way of feeding, common pathogens.
All this contributed to consolidation in the gene pool.populations of groups of normal allelic pairs of genes and in the early stages of anthropogenesis provided the basis for the action of hereditary types of variability and natural selection.
What do population-statistical genetics study?method now? First of all, this is the effect on the human genome of forced isolation, closely related marriages, environmental degradation. It was they who led to the burdening of the gene pool of humanity with pathological genes and led to the creation of a wide network of medical and genetic counseling, designed to identify the hereditary predisposition to the manifestation of various diseases.
