The principle of inheritance of the Rh factor in humans: how does the child inherit it, is it Rh-dominant? How is the Rh factor inherited in humans?

Perhaps, in anticipation of the birth of a baby, the question of how the Rh factor is inherited is in the first place only among women who are afraid of a Rh conflict. For other parents, external data and the health of the unborn child are much more important. But it is worth noting that the characteristics of blood are no less important for a little man than hair color or eye shape, so you should familiarize yourself with the concept of Rh (Rh) and the principles of its inheritance.

Rh positive and negative

In humans, a group of lipoproteins can be on the surface of red blood cells, it occurs in about 85% of people, and in this case we are talking about the Rh-positive factor. But the absence of lipoproteins in 15% of children does not indicate a disease or developmental anomalies, but only indicates a negative Rh. The presence or absence of a lipoprotein group on an erythrocyte in most cases does not affect a person’s lifestyle in any way, only women with a negative Rh during pregnancy have a risk of an Rh conflict.

The lipoprotein formula has a rather complex composition, it will include various antigens, but the Latin D is used to denote the Rh factor:

• "+" is denoted by D;
• "-" put the letter d;

In this case, D is a dominant, and d is a recessive gene.

It would seem that D + d will always give a "+", but there are some nuances of the inheritance of the Rh factor, in which both Rh-positive parents give birth to Rh-negative children.

The mismatch of the Rh factor in parents and the child very often causes suspicions of treason and family quarrels, but in fact this is the norm and Rh-positive parents can give birth to Rh-negative children.

Why is this happening? To do this, we need to consider how parental genes are inherited and what a chromosome set is.

A little about genetics

Probably, many still remember from school that all cells of the human body, except for the cells of the reproductive system, consist of two chromosomes that carry dominant and recessive genes.

The egg and sperm have one chromosome set, and during fertilization, a new cell is formed that has a unique combination of chromosomes, which is responsible for external data and some features of the fetal body.

Rh, like other characteristics, is genetically transmitted, and the following combination may occur when the egg is fertilized:

As you can see, in the second case, the combination of Dd consists of a dominant and a recessive trait, that is, children are born with Rh "+", but they also have a recessive Rh "-" gene. Of course, at the level of genetic research, it is possible to identify which combination is available - DD or Dd, but this analysis is very complicated, it is not necessary.

For the presumptive determination of Rhesus by obstetricians, a table of inheritance is used.

Having considered how Rh is formed, it can be noted that a negative Rh in 100% of cases is inherited only from Rh-negative parents, in all other cases, the formation of both a negative and a positive Rh factor is possible. Moreover, the gender of the parent does not affect how Rh is inherited, inheritance depends only on the dominant gene.

A little about Rhesus conflict

Many women with Rh "-" are afraid to give birth to a man with Rh "+", fearing that they will not be able to bear and give birth to a healthy child. But this fear is not always justified.

• the maternal organism, which does not have a lipoprotein component on the surface of erythrocytes, perceives the fetal lipoproteins as a foreign body;
• the immune system of the pregnant woman begins to actively produce antibodies that destroy the erythrocytes of the embryo;
• during this process, a large number of red blood cells die in the embryo, which leads to miscarriage or fading of pregnancy (fetal death).

The blood type and Rh of the fetus are formed by the end of the 3rd month of development, and it is at this time that a pregnant woman can lose her baby. But is there any hope for heterogeneous couples to have healthy children?

In fact, everything is not so scary and techniques have been developed that allow a woman to bear a full-fledged baby, even with a negative factor.

1. A specific vaccination that suppresses the reaction of the woman's immune system against foreign lipids. The vaccination can be done both before conception, when planning a pregnancy, and immediately after determining an interesting position.
2. Regular medical supervision. Such women have to take tests and visit antenatal clinics more often than other groups of pregnant women in order to timely identify the first deviations during pregnancy.

But only by the end of the 3rd month of gestation it will be possible to determine whether Rh “+” or Rh “-” is transmitted from the father. If a negative factor is detected in the fetus, then the pregnancy will proceed without the risk of embryo death due to the immune system of the pregnant woman.

Knowing about the inheritance of Rhesus helps to suggest the Rh factor of the baby even before his birth. But in most cases, this information plays an important role only in preventing Rh conflict in pregnant women.

Human blood consists of red cells - erythrocytes. In some cases, group D antigens are present on their surface, in such situations they speak of a positive Rh. These substances are present in the blood of approximately 85% of people, the remaining 15% have the Rh factor, that is, they do not have these antigens. There are other antigens in the blood, but their presence is not so important for blood transfusion or.

Transfusion of Rh-positive blood to a person with a negative Rh factor leads to the destruction of red blood cells, which causes the so-called pathological hemolysis - this is how the immune response to unfamiliar substances manifests itself. People with Rh negative need to be careful when transfusing blood. You should also pay attention to your Rh factor when: a negative Rh mother and a positive father can cause an Rh conflict and lead to the development of hemolytic jaundice, stillbirth or death of the baby.

Rh-positive people can be transfused with blood with any Rh factor, and women with such blood should not be afraid of conflict, even if the father is Rh-negative.

How is the Rh factor inherited?

The genes responsible for the Rh factor are inherited according to the same principles as any other genes. So, with inheritance, a positive Rh: in most cases, the “meeting” of two genes responsible for different Rh factors, the one that is responsible for the positive one “wins”. But not in all cases: even with a positive Rhesus, both parents can have a child with a negative, but the likelihood of this is less. This happens because different genes can be present in the alleles of the parents: one of them dominates, causing a positive Rh, and the other simply exists, but does not manifest itself in any way. Since the alleles are divided into two parts during the formation of germ cells, the egg may also meet with the genes responsible for the negative Rh factor. In this case, the child inherits this Rhesus.

It can only be unequivocally stated that parents with a negative Rh factor necessarily have the same child, since their genotype does not have a single gene responsible for the presence of antigens on red blood cells. If one parent is Rh negative and the other is Rh positive, then the child is equally likely to inherit both.

While waiting for the birth of an heir in the family, future parents wonder who he will take growth from, a blond or a brunette will be born. But, perhaps, the main question is what type of blood and how the Rh factor is transmitted to the child. Some families will not pay attention to this. But its negative meaning in the future life of the baby can turn into a problem.

Therefore, the following issues must be taken seriously:

• general concepts of the Rh factor;
• how it is formed;
• what does it depend on;
• How is the Rh factor inherited?
• about its danger during the pregnancy of the expectant mother;
• how a hereditary disease is inherited with the Rh factor;

The importance of these issues is identified with the importance of other blood characteristics in general.

Introduction to the Rh factor

The concepts of blood group and Rh factor have appeared recently. When mixing red blood cells from different fences, the scientist Landsteiner K. in 1940 noticed that in some cases clots formed.

Based on this, in further studying the properties of red blood cells, he divided them into 2 groups, calling them A and B.

Already his students have identified a group containing both: A and B.

This is how the ABO system was born, which divides blood into groups as follows:

• if antigens A and B are absent, then such a group is designated I (0), which corresponds to the first blood group;
• if only antigens A are present, then this is designated II (A) - this is the second group;
• if only B antigens are present, then such a group is designated III (B) - the third group;
• if antigens A and B are present, then this is IV (AB) - the fourth group;

Further studies revealed that protein may be present on the surface of red blood cells. This property is called a positive Rh factor, if the protein is absent in the blood, then it is a negative Rh factor.

All this formed the basis of the so-called Rh classification system.

Thus, there are 4 types of blood groups: I, II, II, IV (or 0, A, B, AB) and two Rh factors: Rh (+) - positive and Rh (-) - negative.

People with a negative Rh can be only 15% of the total population.

The indicators of the blood group and the Rh factor are not related to each other in any way, but when determining the blood group, they necessarily talk about its Rh, for example, II Rh (+). These two values ​​are equally important in blood transfusion and during pregnancy.

Rhesus must be inherited from parents, not change throughout a person’s life, and, to the question of whether a hereditary disease is transmitted with the Rh factor and whether it depends on its positive or negative value, we can say for sure that it is not.

Now genetics are studying the properties of blood. They found that the inheritance of Rh factors and blood groups are subject to the laws of Mendel, discovered by him in the 19th century. From the school curriculum there are well-known experiments with peas that confirm this law. How the gene of its negative value is inherited in the Rh factor is very well explained precisely by this law.

The most basic thing about the concept of blood type

The blood of a child depends on the parents and is inherited with the so-called ABO gene, which is located on the 9th chromosome. The following table will show with what probability the group will be taken from the parents.

With 100 percent probability, you can say which blood type will be transmitted to the baby if they both have the first one.

The influence of genetics on the Rh factor

It is now reliably known that the Rh factor in humans is determined by genetics. A pair of genes is considered: D positive and d negative. They can be the same type of components DD or dd (the so-called homozygous pair of genes) and different components, for example Dd (heterozygous), where D is dominant in this case and it depends on it whether the Rh factor will be positive. These genes are inherited. They are the reason for the birth of a baby with a negative Rh from parents with positive Rh.

The inheritance table below shows all the possible predictions of the Rh factor of the child, depending on what indicators of the Rh factor the parents have:

As can be seen from the table, if two parents have Rh negative, then the child will be born with a negative Rh factor, in other cases it all depends on how the genes are inherited.

Brief description of Rh conflict

You probably know how often they are afraid of the Rhesus conflict. What is it and is it scary? It is impossible to influence this somehow, since it is possible to know in advance what the child's Rh factor will be, as has been shown, only with any probability.

If the unborn child has Rh (+), and the mother has Rh (-), her immunity in this case perceives the child's body as foreign and tries to get rid of it. There is a so-called Rhesus conflict.

Medical practice knows many cases when healthy children were born under such circumstances.

The formation of Rhesus ends by three months from the onset of conception.

If the fetus remains, it can develop with various complications, such as damage to the central nervous system. Help, as always, will come from doctors. By following all their advice, all complications can be avoided.

The patient, observed in a medical institution, systematically passes the necessary tests. In late pregnancy, the examination is carried out every two weeks. Specialists, based on your general condition, may recommend preterm birth. If necessary, a number of medical procedures are carried out to improve the state of health.

Currently, a woman with Rh(-) can be given a special vaccination either before or after conception.

It is impossible to determine what the Rh factor will be in a child, since nature is responsible for this. But, based on scientific knowledge, we can say that following all medical recommendations, you can give birth to a healthy, full-fledged child, with whom you will enjoy a long and happy life together.

In contact with

In cases where the concept of a blood group is used, it means the group (according to the ABO system) and the Rh factor Rh. The first is determined by antigens located on erythrocytes (red blood cells). Antigens are specific structures on the surface of a cell. The second component is . This is a specific lipoprotein, which may or may not be present on the erythrocyte. Accordingly, it will be defined as positive or negative. In this article, we will figure out which blood type of children and parents will be a priority during pregnancy.

If the organism defines such a structure as foreign, it will react aggressively to it. It is this principle that must be taken into account in the procedures for transfusion of lymph. Often people have a false idea that the parents should match. There is Mendel's law, which allows you to predict the performance of future children, but these calculations will not be unambiguous.

As mentioned, the ABO blood system is defined by the location of certain antigens on the outer shell of the erythrocyte.

So, there are 4 blood groups in children and adults:

• I (0) - no antigens A or B.
• II (A) - only A is present.
• III (B) - B is determined on the surface.
• IV (AB) - both antigens - A and B are detected.

Inheritance of blood types

Parents often wonder if the blood type of parents and children can differ? Yes, this is possible. The fact is that the child occurs according to the law of genetics, where genes A and B are dominant, and O - recessive. The baby receives one gene from the mother and father. Most human genes have two copies.

In a simplified form, the human genotype can be described as follows:

• - OO: the child will only inherit O.
• - AA or AO.
• - BB or BO: both one and the second trait can be equally inherited.
• - AB: children can get A or B.

There is a special table of the blood group of children and parents, according to which it is clearly possible to guess which group and Rh factor of the blood the child will receive:

It is worth paying attention to a number of patterns in the inheritance of traits. So, the blood type of children and parents must match 100% if both parents have the first. In cases where parents have 1 and 2 or 1 and 3 groups, children can equally inherit any trait from one of the parents. If a partner has a 4th blood group, then in any case he cannot have a child with 1 type. The blood type of children and parents may not match even if one of the partners has group 2 and the other has group 3. With this option, any result is possible.

Things are much simpler with the inheritance of Rh: the D antigen is either present or absent. A positive Rh factor is dominant over a negative one. Accordingly, the following subgroups are possible: DD, Dd, dd, where D is a dominant gene and d is a recessive one. From the above, it is clear that the first two combinations will be positive, and only the last one will be negative.

In real life, this situation will look like this. If at least one parent has DD, then the child will inherit a positive Rh factor, if both owners of dd, then a negative one. In the event that the parents have Dd, there is a possibility of a child with any Rh.

There is a version that you can determine the parents. Of course, it is impossible to believe in such a calculation with great certainty.

The essence of calculating the blood type of the unborn child is reduced to the following principles:

• A woman (1) and a man (1 or 3) are more likely to give birth to a girl, if a man has 2 and 4, then the likelihood of a boy will increase.
• A woman (2) with a man (2 and 4) is likely to get a girl, and with a man (1 and 3) a boy.
• Mother (3) and father (1) will give birth to a girl, with men of other groups there will be a son.
• A woman (4) and a man (2) should expect a girl, with men of a different blood there will be a son.

It is worth noting that there is no scientific evidence for this theory. The method suggests that the unity of parents according to the state of blood rhesus (both negative and positive) speaks in favor of the appearance of a daughter, in other cases - a son.

conclusions

Currently, medicine makes it possible to determine which may appear in a child even before his birth. Of course, you should not completely trust the tables and independent research. Accuracy in determining the group and Rhesus of the unborn child can only be expected after a laboratory study.

What is really worth paying attention to is the fact that it is possible with a high probability to establish predispositions to diseases of the future child by parental blood.

One of the most important tasks in determining the category of blood is to reduce the possible risk of its transfusion. If alien genes enter the human body, an aggressive reaction can begin, the outcome of which is very sad. The same situation occurs with inappropriate rhesus. These circumstances are important to consider for pregnant women, especially those with a negative factor.

Do not forget about the possible mutations of genes that occur on earth to one degree or another. The fact is that earlier there was one blood type (1), the rest appeared later. But these factors are so rare that it is not worth dwelling on them in detail.

There are certain observations regarding the correspondence between the character of a person and his blood. From this, scientists have drawn conclusions about the predisposition to certain diseases. So, the first group, being the earliest on Earth, seems to be the most enduring; leaders are most often found among the people of this subgroup. These are pronounced meat lovers, but, unfortunately, they also have strong allergic reactions.

People of the second blood group are more patient and practical, they are most often vegetarians, including because of the sensitive gastrointestinal tract. Their immune systems are weak and they are often exposed to infectious diseases.

The third subgroup is represented by passionate natures, extreme people. They tolerate environmental changes better than others and have excellent immunity.

People of the fourth blood subgroup are the rarest, they are very sensual and see this world in their own way. They have a receptive nervous system and are often very altruistic.

It is up to parents to decide whether to trust such characteristics, whether to make predictions about the nature of their child, based on such observations. But using the achievements of modern medicine to improve the health of the unborn baby is never superfluous.

In total, a person has four blood groups and two variants of the Rh factor: positive and negative. The most common variety is the first, the rarest - the fourth. About 75% of the population is Rh positive, while the rest are Rh negative. The inheritance of these two indicators occurs in utero, they do not change during life and are inherited from parents.

What determines the blood group

This trait is transmitted to children from parents and is determined by the antigenic system (AB0 is the most common). According to it, there are or are no special protein structures in the blood - agglutinogens (A and B) on erythrocytes and agglutinins (alpha and beta) in blood plasma. Depending on the composition of the biological fluid, the following types are distinguished:

• Group I (0) - erythrocytes do not contain agglutinogens, both types of agglutinin are present in plasma;
• Group II (A) - agglutinogen A is noted on erythrocytes, in plasma - agglutinin beta;
• Group III (B) - erythrocytes contain agglutinogen B, plasma - agglutinin alpha;
• Group IV (AB) - there are both agglutinogens on erythrocytes, and not a single agglutinin in plasma.

The presence of agglutinogen and agglutinin of the same name in the blood (A and alpha, B and beta) is not possible, because in this case the blood components are incompatible with each other, there is an instant agglutination of red blood cells - an agglutination reaction - which leads to the death of a person. This situation is possible when transfusing an incompatible biological fluid. With the natural formation of fetal blood, this situation does not arise.

Group membership inheritance options

The genotype of both one and both parents can be homozygous (with two identical alleles in the gene - AA or BB) and heterozygous (that is, have two different alleles - dominant and recessive - Aa or BB). Therefore, different combinations are possible in children (the baby may have indicators that are different from those that their mother and father have).

The scheme of inheritance by a child of a blood type from parents is presented in the table:

The blood types of the parents and the child do not always match. Absolutely normal is the option when the mother and father, for example, have II and III varieties, and their baby has IV.

What is the Rh factor?

The Rh factor is an antigen that is inherited by blood type.

If it is determined on the membranes of erythrocytes, the status is positive; if it is absent, it is negative. This indicator is determined by several different genes, but when assessing it, only one pair of genes, D, is usually considered.

Genetic transmission of Rh (Rh + / Rh-): possible variations in children

Positive Rh (Rh +) will be dominant (that is, it is “stronger” and will always give out its trait, even if a recessive gene is also present in the genotype), negative (Rh-) - recessive. Since the Rh factor gene consists of two alleles, the following options are possible: DD, Dd, dd. The first two are Rh+, the third is Rh-.

Possible inheritance options look like this:

It is reliably known that even Rh-positive parents can give birth to children with a negative Rh.

The meaning of blood group and Rh factor in medicine

Both indicators are of great importance in medicine. When it became possible to determine the group affiliation of blood, the transfusion of incompatible biological fluid became more an accident than a pattern. Thanks to these indicators, it is possible to save victims in accidents, in case of an unsuccessful operation or childbirth, and if necessary, replenish a large amount of lost fluid. The donor movement is actively developing in Russia.

Previously, the concepts of "universal donor and recipient" were widely used - these are people who have I (0) and IV (AB) blood groups, respectively, since the first group does not have agglutinogens and does not react with erythrocyte agglutinins, and the fourth does not have agglutinins in plasma and does not provoke agglutination of donor erythrocytes. Currently, doctors are moving away from these terms and transfuse only biological fluid that completely matches the group and Rhesus. The concepts of universality are applicable in emergency situations.