Dominant autosomal trait. Recessive autosomal trait

The number of various diseases that can significantly limit the life of a person and even lead to death is constantly growing. It is worthwhile to understand an important fact: some of the pathologies that violate the body's functions are not acquired, but, as they say, are rooted in genetics. It is about the inheritance of autosomal traits transmitted from generation to generation.

What should be understood as an autosomal feature

Deepening into the essence of this term, it is important first of all to pay attention to such a property of any living being as heredity. In most cases, children are similar to their parents, but in fact, among the representatives of the same family, in fact, there are always some differences.

In other words, each has its own individual characteristics, but they are in fact part of the genetic heritage. Thus, the autosomal sign is nothing more than the inheritance of the genetic traits of the parents.

Transmission of diseases

In addition to specific individual characteristics, a person can inherit certain diseases from his father and mother. This fact is due to the influence of mutation of genes that are localized in autosomes. In this case, such signs can be divided into two key areas: dominant and recessive. Both those and others have a significant impact on the structure of the heritage of a particular person.

Autosomal dominant trait

Each type of inheritance has its own characteristics. If we consider autosomal dominant, then it should be noted that in this case, in order to obtain the disease by inheritance, it is sufficient to transfer the mutant allele of any of the parents. This sign of inheritance can equally occur in both men and women. In fact, autosomal dominant inheritance can be defined as the transmission of a trait that is controlled by the dominant allele of the autosomal gene. With this type of inheritance, one mutant allele localized in the autosome will be sufficient for the manifestation of the disease.

The good news is that most diseases that are transmitted in this way do not cause significant harm to health, nor do they have a significant deleterious effect on human reproductive functions. If we compare the level of influence on the percentage of diseases, then the dominant signs are more likely to lead to any deviations than recessive ones. If there is such a mutation in one of the spouses, with full health of the second, the risk of transmission of the disease is 50%. For this reason, the autosomal dominant sign, manifested in the form of any mutation, can be transmitted from generation to generation and, thus, have a family character. Unlike autosomal recessive, these symptoms are manifested in heterozygotes that have one mutant and one normal allele on homologous chromosomes.

Diseases in autosomal dominant inheritance

With this type of transmission of hereditary traits for the manifestation of the disease in the next generation, a heterozygous mutation carrier is sufficient. It is interesting that the dominant autosomal sign implies the same incidence of diseases in both girls and boys.

If the disease resulting from this type of heredity transmission is present in the child, while both parents are healthy, this fact means a new mutation in the reproductive cells of the mother or father. It is important to understand that in one family the impact of the dominant gene on the condition of children may differ. This means that the clinical picture and the severity of the diseases will not necessarily be the same.

Examples of diseases

The autosomal sign of the dominant type is clearly manifested through a disease such as the Marfan syndrome. Such a diagnosis means that the connective tissue is affected in the human body. In patients suffering from Marfan syndrome, usually thin thin fingers, and the length of the limbs is disproportionate. Such people often develop aortic and cardiac valves.

Another hereditary disease, which is determined by the presence of autosomal dominant signs of inheritance, is brachidactyly, it is short-cut. This is a fairly rare sign that occurs in one of the parents. The manifestation of this disease is noticeable already at the first time after birth due to unnatural changes in the phalanges of the fingers and toes.

Hereditary deafness is an autosomal sign that can also be identified as dominant.

Amyotrophic lateral sclerosis (ALS, or Charcot's disease) is also a consequence of autosomal dominant inheritance and belongs to the group of motor neuronal diseases. This disease can be defined as a fatal, progressive, neurodegenerative disorder that was caused by degeneration of the cells of the central nervous system - motor neurons. The main function of these cells is maintaining muscle tone and providing motor coordination.

Autosomal recessive trait: features

This type of inheritance has several key characteristics:

• May not affect the condition of children, even if there were many carriers of hereditary disease in the pedigree, since recessive signs do not appear in every generation (inheritance horizontally, in contrast to the dominant features);
• The recessive mutant gene (a) manifests itself phenotically only when it is in the homozygous state (aa);
• Hereditary disease is manifested equally often in both female and male individuals;
• The likelihood that a born child will be ill increases significantly in the case of related marriages;
• The phenotically healthy parents of a child with a manifested disease may be heterozygous carriers of the mutant gene.

It should be noted that among the entire hereditary pathology recessive autosomal inheritance of signs is the most common. Diseases that can be identified as a consequence of this trait include a large group of fermentopathies leading to a metabolic disorder, blood diseases (homeostasis including), kidneys, the immune system, etc.

Examples of autosomal recessive diseases

• This group of symptoms can be attributed to Girke's disease (glycogenosis). The manifestation of this genetic disorder is due to a deficiency of the enzyme glucose-6-photosatase, which leads to a significant deterioration in the ability of the liver to reproduce glucose. Violation of such an important process inevitably leads to hypoglycemia.
• The disease of maple syrup is also an autosomal sign, which can be defined as recessive. This disease has another name - leucinosis. Such a diagnosis implies a metabolic disorder that is the result of an incorrect metabolism of branched-chain amino acids. This disease can be attributed to organic acidemia.
• Thea-Sachs disease, which also has such names as early childhood amavrotic idiocy and hexosaminidase deficiency. This disease is a genetic autosomal recessive and leads to progressive deterioration of the child's physical and mental abilities.
• It is worth noting that, unlike a disease such as deafness, the autosomal sign of color blindness is recessive, but it can be classified as "linked to the sex". Violation of color perception can be both partial and complete. The most common is a distorted perception of red. It is worth noting that in some cases, the disturbed perception of a specific color is compensated for by a more qualitative distinction of the shades of other colors.

• Phenylketonuria is an autosomal recessive trait that implies hereditary metabolic disease. Such a violation is caused by a deficiency in the enzyme phenylalanine.

What is meant by diseases linked to the sex

Diseases of this group are due to the fact that a man has one X chromosome, and two women. Accordingly, the male representative, having inherited the pathological gene, is hemizygotic, and the woman is heterozygous. Hereditary signs, which are transmitted along the X-linked type, can occur with different probability in representatives of both sexes.

If we consider the dominant X-linked inheritance of the disease, it is worth noting that such cases are more common in women. This is due to the increased possibility of obtaining a pathological allele from one of the parents. As for men, they are able to inherit a gene of this type only from the mother. Moreover, in the male line, the dominant autosomal trait linked to the X chromosome is passed on to all the daughters, while the sons do not manifest the disease, since they do not receive the chromosome of the father.

If you pay attention to the autosomal recessive X-linked sign of inheritance, it can be noted that such diseases develop mainly in hemizygotic men. In turn, women are in fact always heterozygous and, consequently, phenotically healthy. X-linked hereditary traits include diseases such as Duchenne-Becker muscular dystrophy, hemophilia, Hunter syndrome, and others.

As for Y-linked inheritance, these signs are due to the presence of the Y-chromosome exclusively in men. The action of such a gene can only be transmitted from the father to the son for many generations.

Features of the mitochondrial method of inheritance

This type of inheritance is distinguished among others in that the transmission of features occurs through mitochondria in the plasma of the egg cell. In this case, the ring chromosome is located in each mitochondria, and there are about 25 000 of them in the ovum. Genetic mutations in mitochondria are manifested when there are progressive ophthalmoplegia, mitochondrial myopathies and optic nerve atrophy Leberath. Diseases that are a consequence of this factor can be transmitted from the mother equally often to both daughters and sons.

In general, both autosomal uncoupled signs and other types of hereditary mutations can have a significant effect on the physical condition of several generations and are the cause of many serious diseases.