Determination of the origin and evolution of blood groups using population genetics methods among different nationalities. Inheritance of blood groups Mongoloids: versions of the origin of group B

There are three types of genes responsible for blood group - A, B, and 0 (three alleles).

Every person has two blood type genes - one received from the mother (A, B, or 0), and one received from the father (A, B, or 0).

There are 6 possible combinations:

How it works (from the point of view of cell biochemistry)

On the surface of our red blood cells there are carbohydrates - “H antigens”, also known as “0 antigens”.(On the surface of red blood cells there are glycoproteins that have antigenic properties. They are called agglutinogens.)

Gene A encodes an enzyme that converts some H antigens into A antigens.(Gene A encodes a specific glycosyltransferase that adds an N-acetyl-D-galactosamine residue to an agglutinogen to produce agglutinogen A).

The B gene encodes an enzyme that converts some H antigens into B antigens.(Gene B encodes a specific glycosyltransferase that adds a D-galactose residue to an agglutinogen, resulting in agglutinogen B).

Gene 0 does not code for any enzyme.

Depending on the genotype, carbohydrate vegetation on the surface of red blood cells will look like this:

For example, let’s cross parents with groups 1 and 4 and see why they have a child with group 1.

(Because a child with type 1 (00) should receive a 0 from each parent, but a parent with blood type 4 (AB) does not have a 0.)

Bombay phenomenon

It occurs when a person does not produce the “original” antigen H on his red blood cells. In this case, the person will have neither antigens A nor antigens B, even if the necessary enzymes are present. Well, great and powerful enzymes will come to convert H into A... oops! but there’s nothing to transform, there’s no one!

The original H antigen is encoded by a gene, which is unsurprisingly designated H.
H - gene encoding antigen H
h - recessive gene, H antigen is not formed

Example: a person with the AA genotype must have blood group 2. But if he is AAHh, then his blood type will be the first, because there is nothing to make antigen A from.

This mutation was first discovered in Bombay, hence the name. In India, it occurs in one person in 10,000, in Taiwan - in one in 8,000. In Europe, hh is very rare - in one person in two hundred thousand (0.0005%).

An example of the Bombay phenomenon No. 1: if one parent has the first blood group, and the other has the second, then the child has the fourth group, because neither of the parents has the B gene necessary for group 4.

And now the Bombay phenomenon:

The trick is that the first parent, despite its BB genes, does not have B antigens, because there is nothing to make them from. Therefore, despite the genetic third group, from the point of view of blood transfusion he has the first group.

An example of the Bombay phenomenon No. 2. If both parents have group 4, then they cannot have a child of group 1.

And now the Bombay phenomenon

As we see, with the Bombay phenomenon, parents with group 4 can still get a child with group 1.

Cis position A and B

In a person with blood type 4, during crossing over, an error (chromosomal mutation) may occur when both genes A and B appear on one chromosome, but nothing on the other chromosome. Accordingly, the gametes of such an AB will turn out strange: one will contain AB, and the other will have nothing.

Of course, chromosomes containing AB and chromosomes containing nothing at all will be rejected by natural selection, because they will have difficulty conjugating with normal, non-mutant chromosomes. In addition, AAV and ABB children may experience a gene imbalance (impaired viability, death of the embryo). The probability of encountering a cis-AB mutation is estimated at approximately 0.001% (0.012% cis-AB relative to all AB).

Example of cis-AV. If one parent has group 4, and the other has group 1, then they cannot have children of either group 1 or 4.

And now the mutation:

The probability of having children shaded in gray is, of course, less - 0.001%, as agreed, and the remaining 99.999% falls on groups 2 and 3. But still, these fractions of a percent “should be taken into account during genetic counseling and forensic medical examination.”

From school we know that there are four main blood types. The first three are common, but the fourth is rare. The groups are classified according to the content of agglutinogens in the blood, which form antibodies. However, few people know that there is also a fifth group, called the “Bombay phenomenon”.

To understand what we're talking about, you should remember the content of antigens in the blood. So, the second group contains antigen A, the third contains antigen B, the fourth contains antigens A and B, and the first group does not contain these elements, but it contains antigen H - this is a substance that takes part in the construction of other antigens. In the fifth group there is neither A, nor B, nor H.

Inheritance

Blood type determines heredity. If parents have the third and second groups, then their children can be born with any of the four groups, if the parents have the first group, then the children will only have blood of the first group. However, there are cases when parents give birth to children with an unusual, fifth group or Bombay phenomenon. This blood does not contain antigens A and B, which is why it is often confused with the first group. But in Bombay blood there is no antigen H, contained in the first group. If a child turns out to have the Bombay phenomenon, then it will not be possible to accurately determine paternity, since there is not a single antigen in the blood that his parents have.

History of discovery

The discovery of an unusual blood type was made in 1952, in India, in the Bombay area. During malaria, massive blood tests were carried out. During the examinations, several people were identified whose blood did not belong to any of the four known groups, since it did not contain antigens. These cases were called the "Bombay phenomenon". Later, information about such blood began to appear all over the world, and in the world, for every 250,000 people, one has a fifth type. In India, this figure is higher - one per 7,600 people.

According to scientists, the emergence new group in India is due to the fact that consanguineous marriages are allowed in this country. According to Indian laws, procreation within a caste allows one to preserve one’s position in society and family wealth.

What's next

After the discovery of the Bombay phenomenon, scientists at the University of Vermont made a statement that there are other rare blood types. The latest discoveries are named Langereis and Junior. These species contain completely unknown proteins responsible for blood type.

The uniqueness of the 5th group

The most common and oldest is the first group. It arose during the time of the Neanderthals - it is more than 40 thousand years old. Almost half of the world's population has the first blood group.

The second group appeared about 15 thousand years ago. It is also not considered rare, but according to various sources, about 35% of people are carriers of it. Most often, the second group is found in Japan and Western Europe.

The third group is less common. Its carriers are about 15% of the population. Most people with this group are found in Eastern Europe.

Until recently, the fourth group was considered the newest group. About five thousand years have passed since its appearance. It occurs in 5% of the world's population.

The Bombay phenomenon (blood group V) is considered the newest, as it was discovered several decades ago. There are only 0.001% of people on the entire planet with such a group.

Formation of the phenomenon

The classification of blood groups is based on the content of antigens. This information applies to blood transfusions. It is believed that the H antigen contained in the first group is the “progenitor” of all existing groups, since it is a kind of building material from which antigens A and B appeared.

Pawning chemical composition hemorrhage occurs in utero and depends on the blood groups of the parents. And here geneticists can tell which possible groups a baby may be born with by carrying out simple calculations. Sometimes deviations from the usual norm do occur, and then children are born who exhibit recessive epistasis (Bombay phenomenon). Their blood does not contain antigens A, B, H. This is the uniqueness of the fifth blood group.

People with the fifth group

These people live the same way as millions of others, with other groups. Although there are some difficulties for them:

1. It's difficult to find a donor. If a blood transfusion is necessary, only the fifth group can be used. However Bombay blood can be applied to all groups without exception, and there are no consequences.
2. Paternity cannot be established. If you need to do a DNA paternity test, it will not give any results, since the child will not have the antigens that his parents have.

There is a family in the USA in which two children were born with the Bombay phenomenon, and even with A-H type. Such blood was detected once in the Czech Republic in 1961. There are no donors for children in the world, and transfusions from other groups are fatal for them. Because of this feature, the eldest child became his own donor, and the same thing awaits his sister.

Biochemistry

It is generally accepted that there are three types of genes responsible for blood groups: A, B and 0. Each person has two genes - one gets from the mother, and the second from the father. Based on this, there are six gene variations that determine blood type:

1. The first group is characterized by the presence of 00 genes.
2. For the second group - AA and A0.
3. The third contains antigens 0B and BB.
4. In the fourth - AB.

Carbohydrates are located on the surface of red blood cells, they are also antigens 0 or antigens H. Under the influence of certain enzymes, antigen H is encoded into A. The same thing happens when antigen H is encoded into B. Gene 0 does not produce any encoding of the enzyme. When there is no synthesis of agglutinogens on the surface of erythrocytes, i.e., there is no original H antigen on the surface, then this blood is considered Bombay. Its peculiarity is that in the absence of the H antigen, or “source code,” there is nothing to convert into other antigens. In other cases, various antigens are found on the surface of red blood cells: the first group is characterized by the absence of antigens, but the presence of H, the second - A, the third - B, the fourth - AB. People with the fifth group do not have any genes on the surface of their red blood cells, and they don’t even have H, which is responsible for coding, even if there are enzymes that are encoded - it is impossible to convert H into another gene, because this source H does not exist.

The original H antigen is encoded by a gene called H. It looks like this: H is the gene that encodes the H antigen, h is a recessive gene in which the H antigen is not formed. As a result, when carrying out genetic analysis possible inheritance of blood groups in parents, children may be born with different group. For example, parents with the fourth group cannot have children with the first group, but if one of the parents has the Bombay phenomenon, then they can have children with any group, even with the first.

Conclusion

Over many millions of years, evolution has been taking place, and not only of our planet. All living beings change. Evolution has not abandoned blood either. This liquid not only allows us to live, but also protects us from negative impact environment, viruses and infections, neutralizing them and preventing them from penetrating vital systems and organs. Similar discoveries made by scientists decades ago in the form of the Bombay phenomenon, as well as other types of blood groups, remain a mystery. And it is unknown how many secrets that have not yet been revealed by scientists are kept in the blood of people around the world. Maybe after some time it will become known about another phenomenal discovery of a new group, which will be very new, unique, and the people with it will have incredible abilities.

Many mutations can occur in the human body, changing its gene structure, and, consequently, its characteristics. This also applies to proteins responsible for the formation of blood groups. There are 2 of them in total - agglutinogens A and B, located on the membrane of erythrocytes. Inherited from parents, these antigens create a combination that determines one of four groups blood.

You can calculate the possible blood groups of a child based on the blood groups of the parents.

In some cases, a child is found to have a completely different blood type than the one that could have been inherited from the parents. This phenomenon was called the Bombay Phenomenon. It occurs as a result of a rare genetic mutation in one in 10 million people (Caucasians).

This phenomenon was first described in India in 1952: the father had blood type 1, the mother had blood type 2, and the child had blood type 3, which is normally impossible. The doctor who studied this case suggested that in fact the father did not have the first blood type, but its imitation, which arose as a result of some genetic changes.

Why does this happen?

The basis for the development of the Bombay phenomenon is recessive epistasis. In order for an agglutinogen, for example, A, to appear on an erythrocyte, the action of another gene is necessary, it was called H. Under the influence of this gene, a special protein is formed, which is then transformed into a genetically programmed agglutinogen. For example, agglutinogen A is formed and determines the 2nd blood group in humans.

Like any other human gene, H is present on each of the two paired chromosomes. It encodes the synthesis of an agglutinogen precursor protein. Under the influence of a mutation, this gene changes in such a way that it can no longer activate the synthesis of the precursor protein. If it happens that two mutated hh genes enter the body, then there will be no basis for the creation of agglutinogen precursors, and there will be neither protein A nor B on the surface of red blood cells, since they will have nothing to form from. When examined, such blood corresponds to I (0), since it does not contain agglutinogens.

With the Bombay phenomenon, the child's blood type does not follow the rules of inheritance from the parents. For example, if normally a woman and a man with group 3 can give birth to a child also with group 3 III (B), then if they both pass on recessive h genes to the child, the precursor of agglutinogen B will not be able to form.

How to recognize the Bombay phenomenon?

Unlike the first blood group, when it does not have agglutinogens A and B on red blood cells, but there are agglutinins a and b in the blood serum, in individuals with the Bombay phenomenon, agglutinins are determined by the inherited blood group. In the example discussed above, although there will be no agglutinogen B on the child’s red blood cells (reminiscent of blood group 1), only agglutinin A will circulate in the serum. This will distinguish blood with the Bombay phenomenon from normal blood, because normally individuals with group 1 have both agglutinins - a and b.

There is another theory that explains possible mechanism Bombay phenomenon: when germ cells are formed, a double set of chromosomes remains in one of them, and in the second there are no genes responsible, among other things, for the formation of blood groups. However, embryos formed from such gametes are most often nonviable and die on early stages development.

Patients with this phenomenon can only be transfused with exactly the same blood. Therefore, many of them keep their own material at blood transfusion stations so that they can use it if necessary.

When getting married, it is better to warn your partner in advance and consult a geneticist. Patients with the Bombay phenomenon most often give birth to children with a normal blood type, but not following the rules of inheritance from their parents.

) is a type of non-allelic interaction (recessive epistasis) of a gene h with genes responsible for the synthesis of blood group agglutinogens of the AB0 system on the surface of erythrocytes. This phenotype was first discovered by Dr. Y. M. Bhende in 1952 in the Indian city of Bombay, who gave the name to this phenomenon.

Opening

The discovery was made during research related to cases of mass malaria, after three people were found to lack the necessary antigens, which are usually used to determine whether blood belongs to a particular group. There is an assumption that the emergence of such a phenomenon is associated with frequent consanguineous marriages, which are traditional in this part of the globe. Perhaps it is for this reason that in India the number of people with this blood type is 1 case per 7,600 people, with an average for the world population of 1:250,000.

Description

In people who have this gene in a recessive homozygous state hh, agglutinogens are not synthesized on the erythrocyte membrane. Accordingly, agglutinogens are not formed on such red blood cells A And B, since there is no basis for their formation. This leads to the fact that carriers of this blood type are universal donors - their blood can be transfused to any person who needs it (naturally, taking into account the Rh factor), but at the same time, they themselves can only be transfused with the blood of people with the same "phenomenon".

Spreading

The number of people with this phenotype is approximately 0.0004% of the total population, but in some areas, particularly in Mumbai (formerly Bombay), their number is 0.01%. Considering the exceptional rarity of this type of blood, its carriers are forced to create their own blood bank, since in case of need for an emergency transfusion they can receive required material there will be practically nowhere.

In medicine, four blood groups are described in detail. They all differ in the location of agglutinins on the surface of red blood cells. This property is encoded genetically using proteins A, B and H. Bombay syndrome is very rarely recorded in people. This anomaly is characterized by the presence of the fifth blood group. Patients with the phenomenon lack proteins that are normally detected. The peculiarity is formed at the stage of intrauterine development, that is, it is of a genetic nature. This characteristic of the main body fluid is rare and does not exceed one in ten million cases.

5 blood group or the history of the Bombay phenomenon

This feature was discovered and described not so long ago, in 1952. The first cases of lack of antigens A, B and H in humans were registered in India. It is here that the percentage of the population with the anomaly is the highest and is 1 case in 7600. The discovery of Bombay syndrome, that is rare group blood, occurred as a result of studying fluid samples using mass spectrometry. Tests were carried out due to an epidemic in the country of a disease such as malaria. The defect was named after an Indian city.

Theories of the origin of Bombay blood

Presumably, the anomaly formed against the background of frequent consanguineous marriages. They are common in India due to social customs. Incest has not only increased the prevalence genetic diseases, but to the emergence of Bombay syndrome. This feature is currently found in only 0.0001% of the planet's population. A rare characteristic of the main fluid in the human body may remain unrecognized due to imperfection modern methods diagnostics

Development mechanism

In total, four blood groups are described in detail in medicine. This division is based on the location of agglutinins on the surface of red blood cells. Outwardly, these characteristics do not appear in any way. However, they need to be known in order to carry out blood transfusion from one person to another. If the groups do not match, reactions occur that can lead to the death of the patient.

This phenomenon is completely determined by the chromosomal set of the parents, that is, it is hereditary. The laying occurs even at the stage of intrauterine development. For example, if the father has the first blood group, and the mother has the fourth, then the child will have the second or third. This characteristic is due to combinations of A, B and H antigens. Bombay syndrome occurs against the background of recessive epistasis - non-allelic interaction. This is what causes the absence of blood proteins.

Features of life and problems with paternity

The presence of this anomaly does not affect human health in any way. A child or adult may not be aware of the presence of a unique feature of the organism. Difficulties arise only if the patient needs a blood transfusion. Such people are universal donors. This means that their liquid is suitable for everyone. However, when determining Bombay syndrome, the patient will need the same unique group. Otherwise, the patient will face incompatibility, which will mean a threat to life and health.

Another problem is confirming paternity. The procedure is difficult for people with this blood type. Determination of family relationships is based on the detection of corresponding proteins that are not detected when the patient has Bombay syndrome. Therefore, in doubtful situations, more difficult genetic tests will be required.

IN modern medicine no pathologies associated with the rare blood group have been described. Maybe, this feature caused by the low prevalence of Bombay syndrome. It is assumed that many patients with the phenomenon are unaware of its presence. However, a case of identifying a rare hemolytic disease in a newborn baby whose mother had the fifth blood group. The diagnosis was confirmed based on the results of antibody screening, lectin studies and determination of the location of agglutinins on the surface of the red blood cells of the mother and child.

The pathology diagnosed in the patient is accompanied by life-threatening processes. These features are associated with incompatibility between the blood of the parent and the fetus. In this case, two patients suffer from the disease at once. In the described case, the mother's hematocrit was only 11%, which did not allow her to become a donor for the child.

The big problem in such cases is the lack of this rare type of physiological fluid in blood banks. This is primarily due to the low prevalence of Bombay syndrome. Another difficulty is the fact that patients may not be aware of the feature. Moreover, according to available data, many people with the fifth group willingly agree to be donors because they realize the importance of creating a blood bank. In case of hemolytic disease of newborns against the background of diagnosis of Bombay syndrome in the mother, cases of which are rare, there is also the possibility conservative treatment without the use of blood transfusion. The effectiveness of such therapy depends on the severity of pathological changes in the body of mother and child.

The significance of unique blood

The anomaly is considered poorly understood. Therefore, it is too early to talk about the impact of this feature on the health of the planet’s population and medicine. It is undeniable that the occurrence of Bombay syndrome complicates the already difficult procedure of blood transfusion. The presence of blood group 5 in a person puts life and health at risk when the need for transfusion arises. At the same time, a number of scientists are inclined to believe that such an evolutionary event may have a beneficial effect in the future, since this structure of biological fluid is considered perfect in comparison with other common options.