Inheritance of blood groups. What is the rarest blood type in India do not do blood transfusions

In the human body, many mutations can occur that change its gene structure, and, consequently, the signs. This also applies to proteins responsible for the formation of blood groups. There are 2 of them in total - these are 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.

It is possible to calculate the possible blood types of the child from the blood types of the parents.

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

This phenomenon was first described in India in 1952: the father had the 1st blood group, the mother had the 2nd, the child had the 3rd, 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 kind of genetic changes.

Why is this happening?

The basis of 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 action of this gene, a special protein is formed, which is then transformed into a genetically programmed one or another 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 codes for the synthesis of the 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 creating agglutinogen precursors, and there will be neither protein A nor B on the surface of erythrocytes, since they will have nothing to form from. In the study, such blood corresponds to I (0), since it does not contain agglutinogens.

In the Bombay phenomenon, the child's blood type does not lend itself to the rules of inheritance from the parents. For example, if normally a woman and a man with the 3rd group can also have a child with the 3rd group III (B), then if they both pass on the recessive h genes to the child, the precursor of agglutinogen B cannot be formed.

How to recognize the Bombay Phenomenon?

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

There is another theory explaining the possible mechanism of the Bombay phenomenon: during the formation of germ cells, 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 not viable and die on early stages development.

Patients with this phenomenon can only be transfused with exactly the same blood. Therefore, many of them save their own material at blood transfusion stations in order to use it if necessary.

When entering into marriage, 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 parents.

Blood is a material that provides an opportunity to study the spread of peoples without cultural bias. This biomaterial is used in various areas sciences: population genetics, biology and physiology. It is also important that people rarely take blood types into account when choosing partners. Moreover, few people know their own blood type today, and no one tried to find out until 1900.

red blood cells

Attention! Modern Japan has become an exception due to the widespread Japanese stereotypes about people with different types blood. They play a huge role in choosing marriage partners.

All human populations share the same 29 known blood systems, although they vary in frequency in specific groups. Given the evolutionary proximity of monkeys to our species, we can say that some of them also have a number of identical systems with us.

Before blood transfusion or organ transplantation, a group is identified according to the AB0 system. It provides for 4 types depending on the presence or absence of specific agglutinogens on erythrocyte membranes. Determine the type of blood in special laboratories. The information received is placed in the patient's medical record at birth.

What is the AB0 system and why is it used in medicine?

The AB0 system was discovered by Karl Landsteiner at the beginning of the twentieth century. It provides for the separation of groups of biological fluids based on the presence of antigens. In people with the second type, substance A is located on the erythrocyte membrane, and in people with the third type, substance B is located. In the fourth type, both antigens are combined, in the first they are not. Antibodies are always formed against missing antigens.

Unlike other classification systems, antibodies are always present in the AB0 system in adults. Sensitization by various bacteria from environment, whose membrane inclusions are similar to erythrocyte antigens, creates the prerequisites for the formation of antibodies. This occurs from 3 to 6 months of life in infants whose antibodies are directed against the membrane structures of bacteria.

Since the immune system in this case recognizes the surface structures of microorganisms as specific to the body, it does not form antibodies to them. In the case of blood type A (anti-B), sensitization is confirmed by Gram-negative bacteria such as Darmbacterium Escherichia coli. The B blood group (anti-A) includes proteins of influenza viruses whose epitopes resemble antigen A.

Antibody attack points are determined by glycosylation of blood proteins and lipids. The blood group A carrier contains antibodies that recognize and bind to α-galactose in the glycosidic structure of glycoproteins. However, erythrocytes of type 0 lack antigen, which does not lead to agglutination and death in groups A and B. This makes carriers of blood type 0 with a negative Rh factor universal donors, that is, their blood can be used for carriers of all other types.

Important! Blood groups are determined by allelesA1/A2,B and 0. The product of allele 0 is not detected, this gene is considered "silent" (amorphous). Antigenic glycoproteins become products of other alleles. The gene is located on the long arm of chromosome 9 (9q34).

In addition to antigens A and B, all erythrocytes have the so-called heterogeneous substance "H". It is the precursor of A and B. Chemically, the specificity of A is related to α-N-acetyl-D-galactosamine, B-D-galactoside and H-L-fucose. Blood group substances are also found in other biological fluids: in saliva, sweat and urine.

Groups are detected using test reagents (with appropriate antibodies):

• Subgroup A1 with anti-A1 serum and anti-A1 phytagglutinins;
• Subgroup A2: indirect detection (because A does not react with anti-A1 sera); B: anti-B serum;
• H-substance is detected by anti-H-phytagglutinins.

Bombay Phenomenon

Among tests for rare antibodies, the Bombay type is especially characteristic. Due to a genetic defect, these individuals lack the H precursor. In this case, no H allele dominates. Accordingly, antibodies against the H-substance will be formed immune system. Regardless of AB0 inheritance, Bombay-type erythrocytes do not react with either A or B antibodies (phenotypically 0). Serum reacts with group 0 (phenotypically anti-0). Because the H precursor is present in every AB0 carrier, a person with Bombay phenomenon cannot become a recipient of other blood.

When examining blood groups, regular examination for rare antibodies. Positive result should be noted individually in the clinical history. This patient can only receive his own blood or from other carriers with the same trait. The frequency of anti-H positive carriers in Bombay blood is 1:300,000. The Bombay phenomenon is rare group and is unlikely to be transmitted among Europeans, since most of them have dominant alleles of H.

Blood group and nationality, race

It is clear that blood grouping patterns are complex. A strong historical distribution gap indicates a complex history of human evolution. This can be seen with the help of global maps of the third blood allele frequency.

The A blood allele is more common worldwide than B. About 21% of all people have A alleles. The most common A allele occurs in small, unrelated populations, especially among black Indians (25-30%), Australian Aborigines (many groups make up 35-58%), Sami of Northern Scandinavia (45-85%). The allele appears to have been absent in Indians living in Central and South America.

Type 0 blood (resulting from the absence of the A and B alleles) is common throughout the world. Up to 63% of people are owners of this blood type. Type 0 is high in frequency among the indigenous populations of Central and South America, where it approaches 100%. It is relatively high both among the Aborigines of Australia and in Western Europe (especially in populations with Celtic ancestors). The lowest frequency of 0 is in Eastern Europe and Central Asia, where B blood is more common.

It is interesting! On the Internet, there are truly ridiculous requests related to blood type. For example, are negative blood types feature races of slaves, or whether nationality can be determined by blood type. Knowledge about blood group and Rh factor is not able to answer such questions.

What blood type is most common among Russians and Ukrainians?

The first Rh-positive group in Russia is common in 48 percent of people. The second in frequency is considered to be the second group of Rh-positive. In third place is 3 Rh-positive blood group, which is even less common among Russian and Mongoloid nationalities. The least common is considered the fourth Rh-negative blood.

Among Ukrainians, the first and second Rhesus-positive blood types are most common. Less than others - the fourth Rh-negative. The average Slav has a significant scatter with respect to groups according to the AB0 system.

What is the Jewish blood type?

In Israel, there is a predominance of representatives of the second Rh-positive blood. Belonging to the third Rh-negative blood group means that the nationality of a Jew is mixed and diluted with other genes, since this type is extremely rare in an ethnic group. In a typical Jewish family, this happens infrequently, and a child is usually born with either the second or first group.

The spread of the Rh factor

Most people in the world have an Rh+ blood type. However, it is more common in some regions. Americans and natives almost all had Rh+ before they began to interbreed with people from other parts of the world.

This does not mean that Americans and Aboriginal Australians are historically closely related to each other. Most African populations are about 97-99% Rh+ people. East Asians are 93-99% Rh+. Europeans have the lowest frequency of this type on any continent. They make up 83-85% Rh+. The lowest known frequency is among the Basques of the Pyrenees between France and Spain. Among them, only 65% ​​of people have a positive Rh.

The distribution patterns for Diego's system are even more striking. Africans, Europeans, East Indians, Gypsies, Aborigines and Polynesians do not have the Diego antigen. The only populations with Diego antigens are Native Americans (2-46%) and East Asians (3-12%). This non-random distribution pattern is consistent with the East Asian origin hypothesis for Americans.

These AB0, Rh, and Diego blood distribution patterns are not like those of skin color or other so-called "racial" traits. The consequence of this is that the specific reasons for the distribution of human blood types are different from those commonly used to categorize people into "races". Because it would be possible to divide humanity into radically different groups, using blood printing instead of other genetically inherited traits such as skin color. There is strong evidence that the commonly used typological model of races is not scientifically sound.

The more scientists study the precise details of human typology, the more they understand how complex distributional processes are. They cannot be easily generalized or understood. However, this hard-earned scientific knowledge is usually ignored in most countries due to complex social and political issues.

As a result, discrimination based on perceived "racial" groups still continues. It is important to keep in mind that this "racial" classification often has more to do with cultural and historical differences than biology. In a real sense, "race" is a distinction that is created by culture, not biology. This indicates the biological illiteracy of the majority of the population regarding the relationship of morphological and physiological characteristics ethnic groups.

The origin and origin of human blood groups

Epidemic studies and molecular biology have found that group 0 carriers have an increased chance of surviving infection with malaria (Plasmodium falciparum). This advantage has contributed to the fact that in the humid tropical regions of Africa and the Americas, type zero is more common than in other regions of the world.

According to molecular biology theory, blood type 0 already emerged as a haplogroup from A at least 5 million years ago. What other factors influenced the development and distribution of different blood types is still unclear. A thorough examination of the distribution of blood types and AB0 alleles around the world revealed that the 0 group has been formed several times, and the B blood type has recently appeared.

In the study of allele frequencies, for the first time, a difference between A in A1 and A2 was found, since A2 antigens occur only a quarter more often than A1 on erythrocytes. A recent gene loci sequencing study found six common alleles (A1, A2, B1, O1, O2, O3) and 18 rare variants in German volunteers. 13 alleles were found for loci sequencing in Japanese subjects, the most common alleles being A1 (83%), B1 (97%), O1 (43%) and O2 (53%). The decrease in gene variants is characteristic of the initial effect of migratory movements.

Mongoloids: versions of the origin of group B

Group B is most common in Central Asia and less common among indigenous peoples in the Americas, Australia. However, this allele is also common in Africa. In general, in the world, the third group is considered a rare AB0 allele. Only 16% of humanity has it. Identification of blood type and Rh factor: what will be the blood of a child, a table, a calculator for determining these indicators Determining the compatibility of blood types for conceiving a child, a table for determining this indicator, possible risks in case of incompatibility

Today, every person is aware of the existing division of known blood groups according to the AB0 system. In biology lessons, they talk in some detail about the principles, about compatibility, about the prevalence among the population of each type. So, it is generally accepted that the rarest blood type is the fourth, and the rarest Rh factor is negative. In fact, such information is not true.

genetic principles

Based on the data obtained in the field of archeology and paleontology, geneticists were able to determine that the first division into occurred more than 40 thousand years ago. It was then, according to scientists, that arose. Later, over the course of millennia, as a result of certain mutational changes, the rest of its currently known types arose.

The group affiliation of human blood according to the AB0 system is determined by the presence or absence of unique compounds on the erythrocyte membranes - agglutinogens (antigens) A and B.

The blood type is inherited according to the laws of genetics and is determined by two genes, one of which is passed on to the child by the mother, and the second by the father. Each of these genes is programmed at the DNA level to transmit only one of these agglutinogens or not contain (and therefore not transmit in a generation) any information (0):

• first 0(I) -00;
• A(II) - A0 or AA;
• B(III) - B0 or ​​BB;
• AB (IV) - AB.

, can be seen in the following examples:

• If the parents have zero and fourth groups, their offspring can inherit only the second or third: AB + 00 = B0 or ​​A0.
• If both parents have a zero group, then no other blood type can occur in the offspring: 00 + 00 = 00.
• Parents whose blood types are second and third have equal chances of being born with any of the possible blood groups: AA / A0 + BB / B0 \u003d AB, A0, B0, 00.

At present, the existence of the so-called Bombay phenomenon, discovered by scientists in 1952, is known. Its essence lies in the fact that a person determines the group affiliation of blood, which, according to the laws of genetics, is impossible, what is its explanation and the cause of the effect. That is, on the membranes of his erythrocytes there is an agglutinogen, which none of the parents has.

An example of the Bombay phenomenon, the rarest blood type:

1. For parents with a zero group, a child is born with a third: 00 + 00 = B0.
2. For parents whose groups are zero and , the child is born with the fourth or second: 00 + B0 / BB \u003d AB, A0.

After numerous studies, an explanation of the Bombay phenomenon was obtained. The answer is that in extremely rare cases, when determining the blood type by standard methods (according to the AB0 system) as zero 0 (I), in fact it is not. In fact, one of the agglutinogens, either A or B, is present on the membranes of her erythrocytes, but under the influence of specific factors, they are suppressed and when determining the group, the blood behaves like 0 (I). But when suppressed agglutinogen is inherited in children, it manifests itself. As a result, parents have doubts about the existence of kinship between them and the child.

How often do such cases occur?

The prevalence of people with the Bombay blood phenomenon in the world does not exceed 0.0004% of all people on the globe. The exception is the Indian city of Mumbai, where the frequency percentage rises to 0.01%. It was by the name of this city that this phenomenon was named (the old name is Bombay).

One of the theories that studies the causes and factors influencing the manifestation of this phenomenon in the population says that in Hindus a higher frequency of manifestation of this type of blood is due to religious characteristics, in particular, the prohibition of eating beef meat.

In Europe, there is no such ban, and the frequency of manifestation of Bombay blood in humans is several times less here. This led genetic scientists to the idea that beef contains specific antigens that suppress the manifestation of agglutinogens.

The specificity of people's lives

In reality, people with rare Bombay blood are no different from the rest. The only difficulty they may face is. Because of the uniqueness of the blood type, they cannot be transfused with any foreign blood, since Bombay blood in humans is incompatible with all other groups. Therefore, people who exhibit this phenomenon are forced to create their own blood bank, which will be activated in case of emergency.

In the United States in the state of Massachusetts today there are brother and sister who have the manifestation and essence of the Bombay phenomenon. Their blood type is the same, but they cannot be donors for each other because they have different Rh factors.

Problems of establishing paternity

At the birth of a child with manifestations of the Bombay phenomenon, it is impossible to prove its presence without the use of special methods for studying group membership. Therefore, the presence of Bombay blood in at least one of the family members (even the most distant relatives) must be taken into account when the father has a desire to establish. Then specialists will carry out a test for genetic matches much more thoroughly and more extensively, in the process of examining samples of the genetic material of the father and child, the antigenic composition of the blood and the structure of erythrocyte membranes will be studied.

It is possible to confirm the manifestation of the Bombay phenomenon in a child only through the use of certain genetic tests to determine the type of inheritance of the blood group. For this reason, if a child is born with an unexpected blood type, in the first place, one should suspect that he has this unusual phenomenon, and not suspect the spouse of infidelity. This is the rarest blood type in a person, but it is extremely rare.

June 10th, 2014

As you know, there are four main blood types in humans. The first, second and third are quite common, the fourth is not so widespread. This classification is based on the content in the blood of the so-called agglutinogens - antigens responsible for the formation of antibodies. The second blood type contains antigen A, the third contains antigen B, the fourth contains both of these antigens, and the first has no antigens A and B, but there is a “primary” antigen H, which, among other things, serves as a “building material” for the production of antigens contained in the second, third and fourth blood groups.

The blood type is most often determined by heredity, for example, if the parents have the second and third groups, the child can have any of the four, in the case when the father and mother have the first group, their children will also have the first, and if, say, the parents have the fourth and the first, the child will have either a second or a third. However, in some cases, children are born with a blood type that, according to the rules of inheritance, they cannot have - this phenomenon is called the Bombay phenomenon, or Bombay blood.

Within the ABO/Rhesus blood group systems that are used to classify most blood types, there are several rare blood types. The rarest is AB-, this type of blood is observed in less than one percent of the world's population. Types B- and O- are also very rare, each accounting for less than 5% of the world's population. However, in addition to these two main ones, there are more than 30 generally accepted blood typing systems, including many rare types, some of which are observed in a very small group of people.

Blood type is determined by the presence of certain antigens in the blood. The A and B antigens are very common, making it easier to classify people based on which antigen they have, whereas people with blood type O have neither. A positive or negative sign after the group means the presence or absence of the Rh factor. At the same time, in addition to antigens A and B, other antigens are also possible, and these antigens can react with the blood of certain donors. For example, someone may have an A+ blood type and not have another antigen in their blood, indicating that they are likely to have an adverse reaction with an A+ blood donation that contains that antigen.

There are no A and B antigens in Bombay blood, so it is often confused with the first group, but there is no H antigen in it either, which can be a problem, for example, when determining paternity - after all, a child does not have a single antigen in the blood that him from his parents.

A rare blood group does not give its owner any problems, except for one thing - if he suddenly needs a blood transfusion, then you can only use the same Bombay blood type, and this blood can be transfused to a person with any group without any consequences.

The first information about this phenomenon appeared in 1952, when the Indian doctor Vhend, conducting blood tests in the family of patients, received an unexpected result: the father had 1 blood type, the mother had II, and the son had III. He described this case in the largest medical journal, The Lancet. Subsequently, some doctors encountered similar cases, but could not explain them. And only at the end of the 20th century, the answer was found: it turned out that in such cases, the body of one of the parents mimics (fakes) one blood group, while in fact it has another, two genes are involved in the formation of the blood group: one determines the group blood, the second encodes the production of an enzyme that allows this group to be realized. For most people, this scheme works, but in rare cases, the second gene is missing, and therefore there is no enzyme. Then the following picture is observed: a person has, for example. III group blood, but it cannot be realized, and the analysis reveals II. Such a parent passes on his genes to a child - hence the “inexplicable” blood type appears in the child. There are few carriers of such mimicry - less than 1% of the world's population.

The Bombay phenomenon was discovered in India, where, according to statistics, 0.01% of the population have "special" blood, in Europe Bombay blood is even rarer - about 0.0001% of the inhabitants.

And now a little more detail:

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

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

6 combinations are possible:

How it works (in terms of cell biochemistry)

On the surface of our red blood cells there are carbohydrates - “H antigens”, they are also “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 part of the H antigens into A antigens. (Gene A encodes a specific glycosyltransferase that attaches the N-acetyl-D-galactosamine residue to agglutinogen, resulting in agglutinogen A).

Gene B encodes an enzyme that converts part of the H antigens into B antigens. (Gene B encodes a specific glycosyltransferase that attaches a D-galactose residue to agglutinogen, resulting in agglutinogen B).

Gene 0 does not code for any enzyme.

Depending on the genotype, carbohydrate vegetation on the surface of erythrocytes will look like this:

For example, we cross parents with 1 and 4 groups and see why they cannot have a child with 1 group.

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

Bombay Phenomenon

Occurs when a person does not form the “initial” H antigen on erythrocytes. In this case, the person will not have either A antigens or B antigens, even if the necessary enzymes are present. Well, great and mighty enzymes will come to turn H into A ... oops! but there is nothing to transform, asha no!

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

Example: a person with the AA genotype must have 2 blood groups. 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 how Bombay Phenomenon #1 works: if one parent has the first blood type and the other has the second, then the child cannot have the fourth group, because neither parent has the B gene necessary for the 4th group.

And now the Bombay phenomenon:

The trick is that the first parent, despite their 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 at work #2. If both parents have group 4, then they cannot have a child of group 1.

And now the Bombay Phenomenon

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

Cis position A and B

In a person with blood type 4, an error may occur during crossing over ( chromosomal mutation), when both genes, both A and B, are on one chromosome, and nothing is on the other chromosome. Accordingly, the gametes of such an AB will turn out to be strange: in one there will be AB, and in the other - nothing.

Of course, chromosomes containing AB, and chromosomes containing nothing at all, will be culled by natural selection, because they will hardly conjugate to normal, wild-type chromosomes. In addition, in children of AAV and ABB, a gene imbalance (violation of viability, death of the embryo) can be observed. The probability of encountering a cis-AB mutation is estimated to be approximately 0.001% (0.012% of cis-AB relative to all ABs).

An example of cis-AB. If one parent has the 4th group, and the other the first, then they cannot have children of either the 1st or the 4th group.

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% fall on groups 2 and 3. But still, these fractions of a percent “should be taken into account in genetic counseling and forensic examination.”

Who does not know that people have four main blood types. The first, second and third are quite common, the fourth is not so widespread. This classification is based on the content in the blood of the so-called agglutinogens - antigens responsible for the formation of antibodies.

The blood type is most often determined by heredity, for example, if the parents have the second and third groups, the child can have any of the four, in the case when the father and mother have the first group, their children will also have the first, and if, say, the parents have the fourth and the first, the child will have either a second or a third.

However, in some cases, children are born with a blood type that, according to the rules of inheritance, they cannot have - this phenomenon is called the Bombay phenomenon, or Bombay blood.

Within the ABO/Rhesus blood group systems that are used to classify most blood types, there are several rare blood types. The rarest is AB-, this type of blood is observed in less than one percent of the world's population. Types B- and O- are also very rare, each accounting for less than 5% of the world's population. However, in addition to these two main ones, there are more than 30 generally accepted blood typing systems, including many rare types, some of which are observed in a very small group of people.

Blood type is determined by the presence of certain antigens in the blood. The A and B antigens are very common, making it easier to classify people based on which antigen they have, whereas people with blood type O have neither. A positive or negative sign after the group means the presence or absence of the Rh factor. At the same time, in addition to antigens A and B, other antigens are also possible, and these antigens can react with the blood of certain donors. For example, someone may have an A+ blood type and not have another antigen in their blood, indicating that they are likely to have an adverse reaction with an A+ blood donation that contains that antigen.

There are no A and B antigens in Bombay blood, so it is often confused with the first group, but there is no H antigen in it either, which can be a problem, for example, when determining paternity - because the child does not have any of the antigens in the blood that him from his parents.

A rare blood group does not give its owner any problems, except for one thing - if he suddenly needs a blood transfusion, then you can only use the same Bombay blood type, and this blood can be transfused to a person with any group without any consequences.

The first information about this phenomenon appeared in 1952, when the Indian doctor Vhend, conducting blood tests in the family of patients, received an unexpected result: the father had 1 blood type, the mother had II, and the son had III. He described this case in the largest medical journal, The Lancet. Subsequently, some doctors encountered similar cases, but could not explain them. And only at the end of the 20th century, the answer was found: it turned out that in such cases, the body of one of the parents mimics (fakes) one blood group, while in fact it has another, two genes are involved in the formation of the blood group: one determines the group blood, the second encodes the production of an enzyme that allows this group to be realized. For most people, this scheme works, but in rare cases, the second gene is missing, and therefore there is no enzyme. Then the following picture is observed: a person has, for example. III blood group, but it cannot be realized, and the analysis reveals II. Such a parent passes on his genes to a child - hence the “inexplicable” blood type appears in the child. There are few carriers of such mimicry - less than 1% of the world's population.

The Bombay phenomenon was discovered in India, where, according to statistics, 0.01% of the population have "special" blood, in Europe Bombay blood is even rarer - about 0.0001% of the inhabitants.

And now a little more detail:

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

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

6 combinations are possible:

How it works (in terms of cell biochemistry)

On the surface of our red blood cells there are carbohydrates - “H antigens”, they are also “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 part of the H antigens into A antigens. (Gene A encodes a specific glycosyltransferase that attaches the N-acetyl-D-galactosamine residue to agglutinogen, resulting in agglutinogen A).

Gene B encodes an enzyme that converts part of the H antigens into B antigens. (Gene B encodes a specific glycosyltransferase that attaches a D-galactose residue to agglutinogen, resulting in agglutinogen B).

Gene 0 does not code for any enzyme.

Depending on the genotype, carbohydrate vegetation on the surface of erythrocytes will look like this:

For example, we cross parents with 1 and 4 groups and see why they cannot have a child with 1 group.

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

Bombay Phenomenon

Occurs when a person does not form the “initial” H antigen on erythrocytes. In this case, the person will not have either A antigens or B antigens, even if the necessary enzymes are present. Well, great and mighty enzymes will come to turn H into A ... oops! but there is nothing to transform, asha no!

The original H antigen is encoded by a gene, which is not surprisingly designated H.

H - gene encoding antigen H

h - recessive gene, antigen H is not formed

Example: a person with the AA genotype must have 2 blood groups. 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 how Bombay Phenomenon #1 works: if one parent has the first blood type and the other has the second, then the child cannot have the fourth group, because neither parent has the B gene necessary for the 4th group.

And now the Bombay phenomenon:

The trick is that the first parent, despite their 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 at work #2. If both parents have group 4, then they cannot have a child of group 1.

And now the Bombay Phenomenon

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

Cis position A and B

In a person with the 4th blood group, an error (chromosomal mutation) can occur during crossing over, when both genes A and B are on one chromosome, and nothing is on the other chromosome. Accordingly, the gametes of such an AB will turn out strange: in one there will be AB, and in the other - nothing.

Of course, chromosomes containing AB, and chromosomes containing nothing at all, will be culled by natural selection, because they will hardly conjugate to normal, wild-type chromosomes. In addition, in children of AAV and ABB, a gene imbalance (violation of viability, death of the embryo) can be observed. The probability of encountering a cis-AB mutation is estimated to be approximately 0.001% (0.012% of cis-AB relative to all ABs).

An example of cis-AB. If one parent has the 4th group, and the other the first, then they cannot have children of either the 1st or the 4th group.

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% fall on groups 2 and 3. But still, these fractions of a percent “should be taken into account in genetic counseling and forensic examination.”

The everyday life of a person with unique blood does not differ from its other classifications, with the exception of several factors:
a serious problem is transfusion, you can use only the same blood for these purposes, while it is universal donor and suits everyone;
Impossibility to establish paternity, if it happened that it is necessary to make DNA, it will not give results, since the child does not have the antigens that his parents have.

Interesting fact! In the USA, Massachusetts, there lives a family where two children have the Bombay phenomenon, only at the same time A-H type, such blood was diagnosed once in the Czech Republic in 1961. They cannot be donors for each other, since they have a different Rh factor, and transfusion of any other group, of course, is impossible. The eldest child has reached the age of majority and became a donor for himself in case of emergency, such a fate awaits him younger sister when she turns 18