The type of inheritance is autosomal dominant. Types of inheritance of traits in humans

All the characteristic features of our body appear under the influence of genes. Sometimes only one gene is responsible for this, but most often it happens that several units of heredity are responsible for the manifestation of one or another trait.

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

The study of human genetics is not only interesting, but also important in terms of understanding the inheritance of various inherited diseases. Nowadays, the conversion of young couples to genetic counseling is becoming quite relevant, so that, having analyzed the pedigree of each spouse, it would be safe to say that the child will be born healthy.

Types of inheritance of traits in humans

If you know how this or that trait is inherited, then you can predict the likelihood of its manifestation in the offspring. All signs in the body can be divided into dominant and recessive. The interaction between them is not so simple, and sometimes it’s 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.

Monogenic inheritance is based on 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.

Non-traditional inheritance is not subject to the laws of heredity and is carried out according to its own rules that are not known to anyone.

Monogenic inheritance

This type of inheritance of traits in humans is subject to Mendeleev's laws. Given the fact that two alleles of each gene are present 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. X-linked dominant inheritance.
4. X-linked recessive.
5. Hollandic inheritance.

Each type of inheritance has its own characteristics and characteristics.

Signs of autosomal dominant inheritance

The type of inheritance autosomal dominant is the inheritance of the prevailing traits that are located in autosomes. Their phenotypic manifestations can vary greatly. In some, the symptom may be barely noticeable, and sometimes its manifestation is too intense.

The type of inheritance autosomal dominant has the following characteristics:

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

All these signs are realized only under the condition of complete dominance. Moreover, 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 with the inheritance of freckles, curly hair, brown eyes and many others.

Autosomal dominant features

Most of the individuals who are carriers of an autosomal dominant pathological trait are heterozygotes for it. Numerous studies confirm that homozygotes for dominant anomalies have more serious and severe manifestations compared to heterozygotes.

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

Among the normal traits with this type of inheritance are:

1. Curly hair.
2. Dark eyes.
3. Straight nose.
4. The hump on the bridge of the nose.
5. Male pattern baldness at an early age.
6. Right handedness.
7. The ability to fold the tongue with a tube.
8. Dimple on the chin.
   

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

1. Multi-fingered, can be both on the hands and feet.
2. Fusion of tissues of the phalanges of the fingers.
3. Brachidactyly.
4. Marfan's syndrome.
5. Myopia.

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

Autosomal recessive inheritance

A trait can manifest itself in this type of inheritance only in the case of the formation of a homozygous for this pathology. Such diseases are more severe because both alleles of the same gene are defective.

The likelihood of manifestation of such signs increases with closely related marriages, therefore, 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 a pathological gene, then the child will be sick.
2. The gender of the unborn child does not play any role in inheritance.
3. In one couple, 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 second is the carrier of such a gene, then the probability of having a sick child is 50%

By this type, a lot of diseases related to metabolism are inherited.

X-linked inheritance type

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 transfer the sick gene only to his daughters, because the sons from him receive the U-chromosome.
3. A sick mother is equally likely to reward children of both sexes with this disease.
4. The disease is more severe in men, because they do not have a second X chromosome.
   

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

1. A sick child may also be born to phenotypically healthy parents.
2. Most often, men are sick, and women are carriers of a sick gene.
3. If the father is sick, then you can not worry about the health of the sons, they cannot get the defective gene from him.
4. The probability of having a sick child in a carrier woman is 25%, if it is a boy, then it rises to 50%.

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

Autosomal dominant diseases

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

1. Currently, there are about 4000 thousand of such diseases.
2. Individuals of both sexes are affected equally.
3. Phenotypic demorphism is clearly manifested.
4. If a mutation of a dominant gene in gametes occurs, then it will most likely manifest itself in the first generation. It has already been proven that men increase the risk of receiving such mutations with age, which means that they can reward their children with such diseases.
5. The disease often manifests itself in all generations.

Inheritance of a defective gene of an autosomal dominant disease is in no way associated with the gender of the child 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 to varying degrees in different patients.

Marfan Syndrome

This disease is characterized by damage to the connective tissue, and hence its functioning. Disproportionately long limbs with thin fingers suggest Marfan syndrome. The type of inheritance of this disease is autosomal dominant.

The following symptoms of this syndrome can be listed:

1. Slim build.
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 report muscle and bone pain.
6. Early development of osteoarthritis.
7. Rachiocampsis.
8. Too flexible joints.
9. Possible speech impairment.
10. Visual impairment.

The symptoms of this disease can be called for a long time, but most of them are associated with the skeletal system. The final diagnosis will be made after all examinations have been completed, and characteristic signs are found in at least three organ systems.

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

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

The most important aspect in the treatment is the prevention of aortic aneurysm. A regular consultation with a cardiologist is required. In emergency cases, aortic transplant surgery is indicated.

Huntington Chorea

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

1. Irregular movements in combination with low tone.
2. Asocial behavior.
3. Apathy and irritability.
4. The manifestation of the schizophrenic type.
5. Mood swings.
   

Treatment is aimed only at eliminating or reducing symptoms. Use tranquilizers, antipsychotics. 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 have an autosomal dominant inheritance type. What this is already clear, but in most cases, everything is not so simple. Very often, not one, but several genes are inherited simultaneously. They appear in specific environmental conditions.

A distinctive feature of this 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 relatives developing this disease.
2. Many multifactorial signs affect a particular gender.
3. The more relatives there is such a sign, the higher the risk of this disease in future descendants.

All considered types of inheritance belong to the classical versions, but, unfortunately, many signs and diseases cannot be explained, because they relate to non-traditional inheritance.

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