Which Rh factor is dominant? How is a person’s Rh factor inherited (passed on) and what should the child’s parents have?

Pregnancy calculators

Here you can calculate the child’s blood type based on the blood groups of the parents, find out how the blood type is transmitted from parents to children, and look at the table of the blood type of children and parents.

The widespread division of people into 4 blood groups throughout the world is based on the ABO system. A and B are erythrocyte antigens (agglutinogens). If a person does not have them, then his blood belongs to the first group (0). If there is only A - to the second, only B - to the third, and if both A and B - to the fourth (see). An accurate determination of blood belonging to a specific group is possible only in laboratory conditions using special serums.

According to the Rh factor, the entire population of the globe is divided into those who have it (Rh-positive) and those who do not have this factor (Rh-negative). The absence of Rhesus does not affect health in any way. However, a woman has it with her child, especially with repeated pregnancies, if this factor is absent in her blood, but it is present in the baby’s blood.

Inheritance of blood type in theory

Inheritance of blood groups and Rh factor occurs according to the well-studied laws of genetics. To understand this process a little, you need to remember school curriculum in biology and consider specific examples.

From the parents, the child is given genes that carry information about the presence or absence of agglutinogens (A, B or 0), as well as the presence or absence of the Rh factor. Simplified genotypes of people different groups blood are written like this:

The first blood group is 00. This person received one 0 (“zero”) from his mother, the other from his father. Accordingly, a person with the first group can only pass on 0 to his offspring.
The second blood group is AA or A0. A or 0 can be passed on to a child from such a parent.
The third blood group is BB or B0. Either B or 0 is inherited.
The fourth blood group is AB. Either A or B is inherited.

As for the Rh factor, it is inherited as a dominant trait. This means that if it is transmitted to a person from at least one of the parents, it will definitely manifest itself.

If both parents are negative for the Rh factor, then all children in their family will also not have it. If one parent has the Rh factor and the other does not, the child may or may not have Rh. If both parents are Rh positive, then in at least 75% of cases the child will also be positive. However, the appearance of a baby with Rh negative in such a family is not nonsense. This is quite likely if the parents are heterozygous - i.e. have genes responsible for both the presence and absence of the Rh factor. In practice, this can be assumed simply by asking blood relatives. It is likely that among them there will be an Rh-negative person.

Specific examples of inheritance:

The simplest option, but also quite rare: both parents have the first negative group blood. The child will inherit their group in 100% of cases.

Another example: mom’s blood type is positive, and dad’s blood type is negative. A child can receive 0 from his mother, and A or B from his father. This means that the possible options will be A0 (group II), B0 (group III). Those. The blood type of a baby in such a family will never coincide with the parent’s. The Rh factor can be either positive or negative.

In a family where one of the parents has a second negative blood group, and the other has a third positive blood type, it is possible to have a baby with any of the four blood groups and any Rh value. For example, a child can receive A or 0 from his mother, and B or 0 from his father. Accordingly, the following combinations are possible: AB (IV), A0(II), B0 (III), 00(I).

Table of the probabilities of having a child with a certain blood type given the corresponding data on the blood types of the parents:

	first	second	third	fourth
first	I - 100%	I - 25% II - 75%	I - 25% III - 75%	II - 50% III - 50%
second	I - 25% II - 75%	I - 6% II - 94%	I - 6% II - 19% III - 19% IV - 56%	II - 50% III - 37% IV - 13%
third	I - 25% III - 75%	I - 6% II - 19% III - 19% IV - 56%	I - 6% III - 94%	II - 37% III - 50% IV - 13%
fourth	II - 50% III - 50%	II - 50% III - 37% IV - 13%	II - 37% III - 50% IV - 13%	II - 25% III - 25% IV - 50%

It is worth remembering that blood type calculated using charts, tables or calculators cannot be considered final. You can accurately find out your baby’s blood type only from the results of laboratory tests.

Questions for the article

The young mother was seriously alarmed when she found out that her newborn daughter had blood type IV. "Can't be! - she assured. “I have group III, my husband has group II.” Either it’s a mistake, or my child has been replaced!” But there was no mistake. And the girl was the same one who was shown to her immediately after giving birth, exactly like her father.

"How can it be?" - Mom asked. And the doctor, armed with a pencil and paper, began to draw her a diagram of the inheritance of blood groups.

Let us delve into the essence of these explanations. But first, a little excursion into history. Existence of blood groups became known only at the beginning of our century, in 1900-1902, when the Austrian scientist Karl Landsteiner established that when mixing the blood of two different people in some cases the red blood cells stick together, in others they do not. This means that not everyone has the same blood, and there are compatible and incompatible blood groups. This discovery had great value, because it suggested a method for safe blood transfusion: you just need to determine its compatibility.

More than 20 years later it became known that blood types are inherited and that inheritance occurs in strict accordance with the laws of genetics.
Any hereditary trait is controlled by at least a pair of genes, one of which the child receives from the mother, the other from the father. And in this case, too, parents pass on to the child not a “ready-made” blood type, but one gene responsible for its formation. The interaction of these genes determines what blood type the child will have: the same as the father, the same as the mother, or a third option will arise as a result of a combination of genes.

The difference between one group and another is determined by the characteristics of blood proteins. Several systems have been created to classify these fairly numerous proteins. The most famous of them-system AB0 (read - a, 6, zero), in which four groups are distinguished - I, II, III, IV.

Group I is called zero and is designated 00, which indicates the presence of two identical genes that determine the group trait - one zero received from the father, the other from the mother.

If a child is diagnosed with blood group I, this means that both the father and mother necessarily have gene 0, but this does not mean at all that they also have group I, since their second genes could be different.

Gene Group II is designated by the letter A. And if a child receives such a gene from both parents, then he, of course, will have blood group II (AA). But he will have the same group even if he receives gene 0 from one of his parents, and gene A from the other, since gene 0 has one feature - it cannot manifest itself in the presence of gene A.

Gene III blood group denoted by the letter B. This group is also formed in those who received from their parents two identical BB genes or two different ones - B and 0, because in this combination gene 0 does not manifest itself.

What will happen if a child inherits gene A from one of the parents, and gene B from the other? They are tolerant towards each other, one does not suppress the other, and their combination leads to the emergence of a new feature - IV blood group(AB).

This is what happened to the girl with whose story we began our conversation. From her mother, who has blood type III, she received gene B, from her father, who has blood type II, she received gene A.

So a new combination arose, seemingly “neither in the mother, nor in the father,” but in reality in strict accordance with the laws of heredity - both from the father and from the mother. These laws are objective; there are no exceptions.

Based on these laws, many problems associated with the study of blood characteristics can be solved. They can also help solve some difficult situations when it is necessary to establish the father of a child.

Why just help? Yes, because, as is already clear to you, a child can have blood group II (AO), for example, if the mother has group IV (AB), and the father has either I (00), or II (AO), or III (VO). If the mother has group III (BO), then the child may also have group III in combination with all the father’s blood groups, except II (AA). Thus, the most reliable answer, based on blood groups, is denial of paternity, that is this man can't be the father of this child. In life, anything happens - and sometimes even such a conclusion can be very important.

Somehow in maternity hospital There was an urgent need to transfuse blood to the newborn. It was written in his chart that his mother had group I, and his father had group IV. The child's blood type was determined - it turned out to be I. But such inheritance cannot happen! In group IV there is no gene 0 necessary for this!

Error? Should I check again? The doctor talked to his mother, and she revealed her secret to him (which, of course, remained a secret to everyone else) - true father child blood group III.

This means that the newborn’s blood has been identified correctly, and a transfusion can be performed!

And here is a casuistic case that occurred in California: a woman who gave birth to twins asked to establish their paternity, pointing to a man who did not want to recognize the children as his own. And experts accidentally discovered and then proved that two newborns have different fathers. Then my mother confirmed this. Let's leave the fact itself to her conscience. Let us conclude: how inexorable are the laws of genetics!

Perhaps, while waiting for the birth of a baby, the question of how the Rh factor is inherited comes first only for women who fear Rh conflict. For other parents, the external characteristics and health of the unborn child are much more important. But it is worth noting that blood characteristics are no less important for a little person than hair color or eye shape, so it is worth familiarizing yourself with the concept of Rh (Rh) and the principles of its inheritance.

Rh positive and negative

In humans, there may be a group of lipoproteins on the surface of red blood cells; it occurs in approximately 85% of people, and in this case we are talking about a Rh-positive factor. But the absence of lipoproteins in 15% of children does not indicate illness or developmental abnormalities, but only indicates 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 negative Rh during pregnancy have a risk of Rh conflict.

The lipoprotein formula has a rather complex composition; it includes various antigens, but the Latin D is used to designate the Rh factor:

"+" is denoted by D;
“-” is marked with the letter d;

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

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

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

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

A little about genetics

Many people probably remember from school that all cells human body except for cells reproductive system, consist of two chromosomes carrying dominant and recessive genes.

The egg and sperm have the same chromosome set, and upon fertilization, a new cell is formed that has a unique combination of chromosomes, which is responsible for the external data and some characteristics of the fetus.

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

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

To presumptively determine Rhesus, obstetricians use an inheritance table.

Having considered how Rh is formed, it can be noted that negative Rh in 100% of cases is inherited only from Rh-negative parents; in all other cases, the formation of both negative and positive Rh factors is possible. Moreover, the way Rh is inherited is not affected by the gender of the parent; 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 carry to term and give birth healthy child. But this fear is not always justified.

Before dispelling most women's fears, it is worth considering how the Rhesus conflict proceeds:

the maternal body, which does not have a lipoprotein component on the surface of red blood cells, perceives fetal lipoproteins as a foreign body;
the pregnant woman’s immune system begins to actively produce antibodies that destroy the red blood cells of the embryo;
During this process death occurs large quantity red blood cells 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 child. But is there any hope for mixed rhesus couples to have healthy children?

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

They include:

A specific vaccine that suppresses the reaction immune system women in relation to foreign lipids. The vaccination can be done both before conception, when planning pregnancy, and immediately after determining an interesting position.
Regular monitoring by a doctor. Such women have to undergo tests and visit antenatal clinic more often than other groups of pregnant women in order to promptly identify the first deviations during pregnancy.

But only by the end of 3 months of gestation will it 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 pregnant woman’s immune system.

Knowing about Rh inheritance helps to predict 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.

A. I. BRUSILOVSKY, professor

This story began like Chukovsky’s: my phone rang. And one of my old acquaintances spoke, extremely alarmed. It turns out that her pregnant daughter has Rh negative blood.

Anxiety arose in the family: after all, everyone now knows that a child in such cases can be born sick. They checked my husband’s blood: it also turned out to be Rh negative.

And my friend was even more upset: she imagined that because of this the danger doubled and that the absence of the Rh factor posed some kind of threat to the health of the unborn baby.

“Don’t worry,” I assured. - Rh factor is a special protein found in red blood cells. And we have a lot of different proteins in our blood, about 70. 85% of people have the Rh factor, 15% do not. And if the Rh factor is expectant mother and her husband is negative, there is nothing to fear for the child!

But when a pregnant woman has Rh-negative blood, and her husband has Rh-positive blood, doctors are wary, fearing an Rh conflict between mother and fetus.

However, it occurs only when the fetus has the same blood as the father, that is, Rh-positive. This is exactly the situation that is shown schematically on our tab.

During pregnancy, mother and fetus are one, and, despite the fact that their blood does not mix, many metabolic products and individual cells from the fetus go to the mother, and vice versa.

This exchange occurs through the structures of the placenta, through that part of it called the placental barrier.

And now the fetal red blood cells (in the tab they are indicated by a circle with a + sign) containing the Rh factor begin to enter the mother’s bloodstream. But there is no such factor in her blood; this protein is foreign to her body.

And then the biological one turns on defense mechanism: after all, in any case, when a foreign substance enters the body, it begins to develop weapons against it - so-called antibodies.

The further pregnancy develops, the more red blood cells containing the Rh factor accumulate in a woman’s blood and, accordingly, the number of antibodies hostile to them increases. (In the tab, antibodies are indicated by dots surrounding the Rh-positive red blood cell.)

In the same way, that is, through the placenta, antibodies penetrate into the blood of the fetus. But they are aimed at destroying Rh-positive red blood cells, and under their influence, the fetal red blood cells begin to disintegrate and die.

Toxic breakdown products accumulate in the blood, in particular bilirubin, which has a harmful effect on the entire body and especially on the brain.

It is because of bilirubin that by the end of pregnancy the skin of the fetus acquires a yellow color (see lower right figure), based on the intensity of which, even before conducting the necessary studies, doctors can assume a hemolytic disease in the newborn (hemolysis - destruction, dissolution).

In such cases, the child will be saved by an emergency blood transfusion. On the tab, this procedure is symbolically represented by a syringe.

But how is the Rh status of the fetal blood formed? Why can't parents with Rh-negative blood have a child who has Rh-positive blood, but if the father and mother have Rh-positive blood, their child can have Rh-negative blood? What is this - an accident, a paradox? No, strict laws genetics.

Let us remember that there are dominant and recessive genes, and that in the presence of dominant genes, recessive ones do not manifest themselves. For greater clarity, let's denote the Rh-positive gene as Rh, and the Rh-negative gene as rh.

It is known that every sign, be it blood type, eye color or shape auricle is determined by at least two genes: one of them is contained in the chromosome received from the father, the other - in the chromosome received from the mother.

Consequently, both father and mother always participate in the construction of pairs of genes that determine each trait, including the Rh factor. Even if a child has “paternal” blood, there are still maternal genes among the genes that determine its properties. And, of course, vice versa.

The Rh (positive) gene dominates over the rh (negative) gene, preventing it from manifesting itself. And, therefore, with Rh-negative blood there can be only one genotype - rhrh (if a “positive” gene was inherited from one of the parents, the “negative” one would be suppressed and the blood would be Rh-positive).

People with Rh-positive blood can have two combinations of genes - either RhRh, that is, identical positive ones received from both parents, or positive and negative - rhrh (the negative is suppressed by the positive, it could not manifest itself, but it exists!).

If a man and a woman with Rh-negative blood marry, the blood of the child will be the same, since neither the father nor the mother has a single “positive” gene (see square II on the tab).

And in people with Rh-positive blood, as we already know, there may be an undetected “Rh-negative” gene. And if each parent passes on one such gene to the child, the child’s blood will be Rh negative.

True, according to the laws of genetics, the probability of such an option is low (see square III on the tab).

How Rh blood can be inherited if the mother has Rh negative blood and the father has Rh positive blood is shown in square I.

It is believed that 10-13% of marriages are between people with different Rh blood factors. However, the frequency hemolytic disease Newborns in relation to all marriages are only 0.3-0.7%.

The fact is that the response to an Rh-positive factor does not occur in all women with Rh-negative blood. The production of antibodies is facilitated by previous pregnancies and abortions (if the fetus in those cases was Rh-positive) or transfusion of Rh-positive blood.

But under all conditions, the development of hemolytic disease in a child can be prevented. The expectant mother just needs to go to the antenatal clinic as early as possible, where they will monitor whether antibodies appear in her blood, and if they are found, they will take the necessary preventive measures.

Since rhesus is a protein located on the surface of red blood cells, it can not only be present, but also absent. If it is absent, they speak of a negative Rh factor. Thus, you can also present in the form of a table the possible options for the birth of a child with a certain rhesus of a person in order to understand what this depends on. You don't need a calculator here, just knowing your Rh factor. In addition to all this, it is worth considering that exceptions quite often occur, which is explained by genetic science. Just as a person’s appearance at birth is unpredictable, so are his structural features. This definition was proven quite a few years ago, when human evolution was still progressing.

Child's blood types by inheritance

Then the laws of inheritance of blood groups of a newborn directly from the parents were discovered. Scientists have also proven that the child’s blood type directly depends on the mixing of the parents’ plasma. It gives its results or the stronger one simply wins.

The most important thing is that there is no incompatibility, because otherwise pregnancy simply does not occur or threatens the child inside the womb. In such situations, special vaccines are given at the 28th week of pregnancy or during its planning period. Then the development of the child will be protected and the formation of his gender.

Type of blood according to the AB0 system There were quite a lot of scientists who worked on the issue of inheritance of blood groups and sex. One of them was Mendeleev, who determined that parents with the first blood group would have children with the absence of antigens A and B.

About the inheritance of blood group. What blood type will the child have?

With regard to blood groups, Mendel found that genes A and B are dominant (they encode the presence of antigens on the surface of red blood cells), and gene 0 is recessive. This means that when genes A and B are combined, both genes will encode the presence of agglutinogens, and the blood group will be the fourth. If genes A and 0 or B and 0 are passed on to the child, then the recessive gene will not manifest itself; accordingly, in the first case there will be only agglutinogens A (the child will have group 2), and in the second - agglutinogens B (the child will have the third group) .
A child inherits a blood type according to certain laws System AB0 This system for the typology of blood groups began to be used in 1900, when the presence in the blood (on red blood cells) of antigens, which were called agglutinogens, as well as antibodies to them, which began to be called agglutinins, was discovered.

How is the blood type of children and parents related? rules of inheritance

Inherited blood type Published by admin August 2, 2012 Many future parents, expecting the appearance of their first child, often dream and talk about who the baby will be like, what kind of character he will have (father’s or mother’s), what awaits him in future. Re-reading various horoscopes and predictions, future parents look for beautiful and suitable names, plan the placement of a crib, discuss other necessary issues and concerns. And only a few think about what blood type the child will get from their union.

But blood type is the same personal identifier as fingerprints. Passed by inheritance from parents to children, blood type throughout life path person remains unchanged.

Whose blood type is passed on to the child?

Probability of inheritance Since there are many in the world various situations, we present the specific blood groups of a person and the possible type of his child using a table. You don't need a calculator or additional knowledge for this. You just need to know your blood type and Rh factor.

Attention

Such an analysis can be done in any specialized laboratory, which is prepared within 2 days. Rh factor of blood Today, not only the heredity of the blood group is known, but also its Rh factor and the gender of the person. This definition this was also proven a long time ago, so many people today are worried about this: they want the child to get good blood.

Quite often there are cases when a spouse with positive Rhesus gives birth to a child with negative Rhesus. Then the question arises on what this depends or even distrust of each other’s fidelity.

Your home doctor

The most unpredictable is the compatibility of groups of parents 2nd and 3rd. In this case, inheritance may be in itself different version, and there is the same probability. There is also a rather rare situation when the rarest heredity occurs - both parents have antibodies of type A and B, but at the same time they do not manifest themselves.
Thus, the child is given not only an unpredictable blood type, but also a gender, and it is extremely difficult to predict its appearance, especially since a calculator will not help here either. Probability of inheritance Since there are many different situations in the world, we present the specific blood types of a person and the possible type of his child using a table. You don't need a calculator or additional knowledge for this.

You just need to know your blood type and Rh factor.

Blood group inheritance rules

If both father and mother are carriers of the first, all their offspring will have only the first and no other.
A couple where one of the parents is with the fourth will never have a baby with the first.
If one is paired with the first and the other with the second, they will only produce offspring with I or II.
If one spouse has the first and the other has the third, their future children will have either I or III.
If both in a couple are carriers of the second or both of the third, they may well have a child with the first.
If one of the spouses has a second, and the other has a third, their children can have any of the four.
If both parents have the fourth, the offspring will have any but the first.

Laws of blood inheritance by group and Rh factor

In all other cases, Rh can be anything. The question arises why the Rh factor is inherited this way if both the man and the woman are Rh positive. In fact, the explanation is very simple. The fact is that positive Rh is determined by the D gene, which can have different alleles: one dominant (D), the other recessive (d). That is, a person with Rh(+) has the genotype DD (homozygous) or Dd (heterozygous).

The genotype of a person with Rh(-) is designated as dd. Thus, the probability that a couple with Rh(+) will have a child with negative Rh is 25%. This can happen if both the mother and father have a heterozygous genotype - Dd. Possible options Rh factor in this case – DD, Dd, Dd, dd.

Heterozygosity is caused by the birth of Rh-conflicting children in an Rh-negative woman. You can independently determine the likelihood of offspring with a particular Rh.

Blood type is inherited

Important

For quite some time now, scientists have proven the existence of four groups. Accordingly, each of the groups is formed at the birth of a child, or rather, in the womb after conception. As people say, it is inherited.

Thus, we receive a certain type of plasma from our parents and live with it all our lives. It is worth noting that neither blood groups nor the Rh factor change throughout life. This is a proven fact that can only be refuted by a pregnant woman.

The fact is that there are rare cases when a woman’s Rh factor actually changes during pregnancy - at the beginning of the term and at the end before giving birth. Back in the mid-19th century, an American scientist reached the conclusion that there is incompatibility in plasma types. To prove this, he may have needed a calculator, but today no one uses it in this case.

Blood type is not inherited

Based on these laws, many problems associated with the study of blood characteristics can be solved. They can also help in solving some difficult situations when it is necessary to establish the father of a child. Why just help? Yes, because, as is already clear to you, a child can have blood group II (AO), for example, if the mother has group IV (AB), and the father has either I (00), or II (AO), or III (VO). If the mother has group III (BO), then the child may also have group III in combination with all the father’s blood groups, except II (AA). Thus, the most reliable answer, based on blood groups, is denial of paternity, that is, this man cannot be the father of this child. In life, anything happens - and sometimes even such a conclusion can be very important. Once in the maternity hospital there was a need to urgently transfuse blood to a newborn. It was written in his chart that his mother had group I, and his father had group IV.

How blood type is inherited (table)

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