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.
Уже научно доказано, что для человека проявление such 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.
Изучение генетики человека не только интересно, 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.
If you know how a feature is inherited,then we 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 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:
These types of inheritance, in turn, are also divided into some types.
The basis of monogenic inheritance are the first and second laws of Mendel. Polygenic based on the third law. This implies the inheritance of several genes, most often nonallelic.
Non-traditional inheritance is not subject to the laws of heredity and is carried out by its own, unknown, rules.
This kind of inheritance traits inman obeys Mendeleev's laws. Given the fact that the genotype contains two alleles of each gene, the interaction between the female and male genome is considered separately for each pair.
On this basis, the following types of inheritance are distinguished:
Each type of inheritance has its own characteristics and characteristics.
The type of autosomal dominant inheritance isinheritance of the predominant traits that are located in autosomes. Their phenotypic manifestations can vary greatly. For some, a sign may be barely noticeable, and it may be too intense.
The type of autosomal dominant inheritance has the following characteristics:
Все эти признаки реализуются только при условии complete domination. In this case, only the presence of one dominant gene will be sufficient for the manifestation of the trait. The type of autosomal dominant inheritance can be observed in humans when inheriting freckles, curly hair, brown eyes and many others.
Большая часть лиц, которые являются носителями autosomal dominant pathological trait are heterozygotes for it. Numerous studies confirm that homozygotes for the dominant anomaly have more severe and severe manifestations compared with heterozygotes.
This type of inheritance in humans is not only characteristic of pathological signs, but also some quite normal ones are inherited.
Among the normal signs with this type of inheritance can be noted:
Among the anomalies that have an autosomal dominant inheritance type, the following are best known:
If dominance is incomplete, then the manifestation of a trait cannot be observed in every generation.
A sign of this type of inheritance can occur only in the case of the formation of homozygotes for this pathology. Such diseases are more difficult because both alleles of the same gene are defective.
The probability of manifestation of such signs increases with closely related marriages, therefore in many countries it is forbidden to conclude an alliance between relatives.
The main criteria for such inheritance include the following:
By this type inherited a lot of diseases related to metabolism.
This inheritance can be both dominant and recessive. Signs of dominant inheritance include the following:
If there is a recessive gene in the X chromosome, then inheritance has the following characteristics:
So inherited diseases such as hemophilia, color blindness, muscular dystrophy, Callman syndrome and some others.
For the manifestation of such diseases it is enough to have one defective gene, if it is dominant. Autosomal dominant diseases have several characteristics:
Inheritance of a defective autosomal dominant disease gene is in no way connected with the sex of the child and the degree of development of the disease in the parent.
Autosomal dominant diseases include:
All these diseases can manifest themselves in varying degrees in different patients.
This disease is characterized by a lesion.connective tissue, and hence its functioning. Disproportionately long limbs with skinny fingers suggest Marfan syndrome. The type of inheritance of this disease is autosomal dominant.
You can list the following symptoms of this syndrome:
You can still call the symptoms of thisdiseases, 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 may be noted that some of the signs of the disease do not manifest themselves in childhood, but become apparent somewhat later.
Even now, when the level of medicine is enoughhigh, completely cure Marfan syndrome is impossible. 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 of treatment is the prevention of the development of an aortic aneurysm. Mandatory regular consultations cardiologist. In emergency cases, aortic transplants are indicated.
This disease also has a type of inheritance.autosomal 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 signs:
The treatment is aimed only at eliminating orreduction of symptoms. Use tranquilizers, antipsychotics. No treatment can stop the development of the disease, therefore approximately 15-17 years after the first symptoms appear, death occurs.
Многие признаки и заболевания имеют тип inheritance autosomal dominant. What this is already clear, but in most cases is not so simple. Very often, the inheritance occurs simultaneously of not one, but several genes at once. They manifest themselves 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:
All considered types of inheritance belong to the classical variants, but, unfortunately, 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 family tree and assess the risk of having a child with disabilities.
