MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.4. ONTOGENETIC LEVEL OF LIFE ORGANIZATION

1.4.2. Fundamentals of human genetics

Diseases with Hereditary Predisposition

Diseases with a hereditary predisposition (Multifactorial Diseases) are caused by a combination of genetic and non-genetic factors, the latter being associated with the external environment. The Development of these pathologies requires not only a specific genetic constitution of the individual, but also an environmental factor or a complex of factors that act as triggers in The formation of the pathology. Such conditions include atherosclerosis, Gout, rheumatism, CORONARY Heart DISEASE, Hypertension, Epilepsy, gastric and duodenal ulcers, Liver cirrhosis, Diabetes Mellitus, Bronchial Asthma, tuberculosis, psoriasis, Schizophrenia, and others.

Characteristic Features of multifactorial diseases include: 1) extensive polymorphism of clinical forms and individual manifestations, with transitional forms ranging from healthy individuals to patients, and from subclinical forms to severe progression; 2) high frequency in the population (diabetes mellitus affects 5% of the world's population, allergic diseases affect over 10%, schizophrenia affects 1%, and hypertension affects about 30%); 3) non-compliance with G. Mendel's Laws of inheritance; 4) variable age of onset among patients.

What is inherited is a predisposition to a particular disease. For certain clinical forms, The Role of the hereditary (familial) factor is decisive. The degree of risk for a patient's relatives depends on the disease frequency in the population and increases with the severity of the condition in the proband. The closer the degree of kinship to the affected relative, the higher the probability of having an affected child. In some cases, the frequency of pathology varies depending on sex; for instance, congenital hip Dysplasia is more common in girls, whereas pyloric stenosis is more frequent in boys.

Diseases with a hereditary predisposition can be either monogenic or polygenic, typically relying on polygenic inheritance and frequently heterozygosity. In polygenic inheritance, a trait is determined by several non-allelic genes, but their phenotypic expression depends on environmental conditions. In heterozygous carriage, a pathological recessive Gene remains unexpressed in the heterozygous state, but it may manifest under unfavorable living conditions. Because diseases with a hereditary predisposition are determined by a combination of hereditary and environmental factors, they are classified as disorders with penetrance that is largely dependent on environmental conditions. By modifying environmental conditions, one can significantly alter the manifestation of such diseases and even prevent them.