Type of inheritance is autosomal dominant. Types of inheritance of traits in humans

All the characteristic signs of our bodyare manifested under the action of genes. Sometimes only one gene is responsible for this, but more often it happens that several units of heredity are responsible for the manifestation of one or another characteristic.

It has already been scientifically proven that for a person manifestationsuch signs as skin color, hair, eye, degree of mental development, depends on the activity of many genes at once. This inheritance does not exactly follow the laws of Mendel, but goes far beyond its limits.

The study of human genetics is not only interesting,but also important in terms of understanding the inheritance of various hereditary diseases. Now, the treatment of young couples in genetic counseling is becoming quite urgent, so that, after analyzing the pedigree of each spouse, it could be confidently asserted that the baby will be born healthy.

Types of inheritance of traits in humans

If you know how this or that attribute is inherited,then it is possible to predict the probability of its manifestation in offspring. All the signs in the body can be divided into dominant and recessive. Interaction between them is not so simple, and at times it is not enough to know which one belongs to which category.

Now in the scientific world there are the following types of inheritance in humans:

1. Monogenic inheritance.
2. Polygenic.
3. Unconventional.

These types of inheritance, in turn, are also subdivided into several varieties.

At the basis of monogenic inheritance are the first and second laws of Mendel. Polygenic is based on the third law. This implies the inheritance of several genes, most often non-allelic.

Unconventional inheritance does not obey the laws of heredity and is carried out according to its own rules that nobody knows.

Monogenic inheritance

This kind of inheritance of traitsman obeys Mendeleev's laws. Considering the fact that there are two alleles of each gene in the genotype, the interaction between the female and male genomes is considered separately for each pair.

Based on this, the following types of inheritance are distinguished:

1. Autosomal dominant.
2. Autosomal recessive.
3. Coupled with the X chromosome is dominant inheritance.
4. X-linked recessive.
5. Hollandic inheritance.

Each type of inheritance has its own characteristics and attributes.

Signs of autosomal dominant inheritance

The type of inheritance is autosomal dominant - this isinheritance of prevalent characteristics, which are located in the autosomes. The phenotypic manifestations of these may be very different. In some, the sign may be barely noticeable, but its manifestation may be too intense.

The type of inheritance autosomal dominant has the following characteristics:

1. A sick sign is manifested in every generation.
2. The number of patients and healthy is approximately the same, their ratio is 1: 1.
3. If children from sick parents are born healthy, then their children will be healthy.
4. The disease affects both boys and girls alike.
5. The disease is equally transmitted from men and women.
6. The stronger the impact on reproductive functions, the greater the likelihood of different mutations.
7. If both parents are sick, then the child, being born homozygous for this symptom, is more ill than in the case of heterozygotes.

All these signs are realized only under conditionfull domination. In this case only the presence of one dominant gene will be sufficient for the manifestation of the trait. The type of inheritance autosomal dominant can be observed in humans when inheriting freckles, curly hair, brown eyes and many others.

Autosomal dominant signs

Most of the people who are carriersautosomal dominant pathological feature, are heterozygous for it. Numerous studies confirm that homozygotes with a dominant anomaly have more serious and severe manifestations compared with heterozygotes.

This type of inheritance in humans is characteristic not only of pathological signs, but some quite normal ones are inherited as well.

Among the normal signs with this type of inheritance, it can be noted:

1. Curly hair.
2. Dark eyes.
3. Straight nose.
4. A pimple on the bridge of the nose.
5. Alopecia at an early age in men.
6. Right-handedness.
7. Ability to fold the tongue of a tube.
8. A dimple on the chin.

Among the anomalies that have an autosomal dominant inheritance type, the following are most known:

1. Mnogobalost, can be both on arms or hand, and on legs or foots.
2. The fusion of the phalanges of the fingers.
3. Brachydactyly.
4. Marfan's syndrome.
5. Myopia.

If dominance is incomplete, then the manifestation of the trait can not be observed in every generation.

Autosomal recessive type of inheritance

To show a sign with this type of inheritance can only in the case of the formation of a homozygote for this pathology. Such diseases proceed more severely, because both alleles of one gene have a defect.

The likelihood of such signs increases with closely related marriages, so in many countries an alliance between relatives is prohibited.

The main criteria for such inheritance include the following:

1. If both parents are healthy, but are carriers of the pathological gene, the child will be sick.
2. The sex of the unborn child does not play any inheritance.
3. In one couples, the risk of having a second child with the same pathology is 25%.
4. If you look at the pedigree, you can see the horizontal distribution of patients.
5. If both parents are sick, then all children will be born with the same pathology.
6. If one parent is sick and the other is a carrier of such a gene, the probability of producing a sick child is 50%

By this type, many diseases related to metabolism are inherited.

Type of inheritance linked to the X chromosome

This inheritance can be either dominant or recessive. The signs of dominant inheritance include the following:

1. Both sexes can be affected, but women are 2 times more likely.
2. If the father is sick, then he can pass the sick gene only to his daughters, because the sons from him receive the U-chromosome.
3. A sick mother is equally likely to award children of both sexes with such a disease.
4. Disease is worse for men, because they do not have a second X chromosome.

If the recessive gene is in the X chromosome, the inheritance has the following characteristics:

1. A sick child can also be born in phenotypically healthy parents.
2. Most often, men are sick, and women are carriers of a sick gene.
3. If the father is sick, then the health of the sons can not be worried, from him they can not get a defective gene.
4. The probability of the birth of a sick child in a female carrier is 25%, in the case of boys, it rises to 50%.

So are inherited such diseases as hemophilia, color blindness, muscular dystrophy, Kallman's syndrome and some others.

Autosomal dominant diseases

For the manifestation of such diseases, it is sufficient to have one defective gene, if it is dominant. Autosomal dominant diseases have some characteristics:

1. At present, there are about 4000 thousand such diseases.
2. The individuals of both sexes are affected equally.
3. Phenotypic demorphism is clearly manifested.
4. If a mutation of the dominant gene occursgametes, then it certainly will manifest itself in the first generation. It has already been proved that men with age are at increased risk of getting such mutations, and, therefore, they can award their children with such diseases.
5. Disease often manifests itself in all generations.

The inheritance of a defective gene of an autosomal dominant disease is not related to the child's sex and the degree of development of this disease in the parent.

Autosomal dominant diseases include:

1. Marfan's syndrome.
2. Huntington's disease.
3. Neurofibromatosis.
4. Tuberous sclerosis.
5. Polycystic kidney disease and many others.

All these diseases can manifest themselves in varying degrees in different patients.

Marfan syndrome

This disease is characterized by a lesionconnective tissue, and consequently, its functioning. Disproportionately long limbs with thin fingers give reason to assume Marfan syndrome. The type of inheritance of this disease is autosomal dominant.

You can list the following signs of this syndrome:

1. Thin figure.
2. Long "spider" fingers.
3. Defects of the cardiovascular system.
4. The appearance of stretch marks on the skin for no apparent reason.
5. Some patients note pain in the muscles and bones.
6. Early development of osteoarthritis.
7. Rachiocampsis.
8. Too flexible joints.
9. There may be a speech disorder.
10. Vision disorders.

You can still call the symptoms of thisdiseases, but most of them are associated with the bone system. The final diagnosis will be made after all the examinations have been completed, and the characteristic features are found in at least three organ systems.

It can be noted that some signs of the disease do not appear in childhood, but become apparent somewhat later.

Even now, when the level of medicine is sufficienthigh, completely cure Marfan syndrome is impossible. Using modern drugs and treatment technologies, it is possible to prolong the life of patients with such a deviation and improve its quality.

The most important aspect in the treatment is the prevention of the development of aortic aneurysms. Regular consultations of the cardiologist are obligatory. In emergency cases, surgery for aortic transplantation is indicated.

Huntington's Horea

This disease also has an inheritance typeautosomal dominant. It begins to appear from the age of 35-50 years. This is due to the progressive death of neurons. Clinically, you can identify the following symptoms:

1. Disorient movements in combination with a reduced tone.
2. Asocial behavior.
3. Apathy and irritability.
4. Manifestation of a schizophrenic type.
5. Mood swings.

Treatment is directed only at elimination orreduction of symptoms. Use tranquilizers, neuroleptics. No treatment can stop the development of the disease, therefore approximately 15-17 years after the onset of the first symptoms death occurs.

Polygenic inheritance

Many signs and diseases are of the typeautosomal dominant inheritance. What is it is already clear, but in most cases everything is not so simple. Very often there is an inheritance of not one, but several genes. They are manifested in specific environmental conditions.

A distinctive feature of such inheritance is the ability to enhance the individual action of each gene. The main features of such inheritance include the following:

1. The more severe the disease, the greater the risk of developing this disease among relatives.
2. Many multifactorial signs affect a certain gender.
3. The greater the number of relatives has such a sign, the higher the risk of the occurrence of this disease in future descendants.

All considered types of inheritance belong to the classical variants, but, unfortunately, very many signs and diseases defy explanation, because they belong to non-traditional inheritance.

When planning the birth of a baby, do not neglect a visit to a genetic consultation. A competent specialist will help you understand your pedigree and assess the risk of having a child with disabilities.