As you know, there are four main blood groups in humans. The first, second and third are quite common, the fourth is not so widespread. This classification is based on the content of so-called agglutinogens in the blood - antigens responsible for the formation of antibodies. The second blood group contains antigen A, the third contains antigen B, the fourth contains both of these antigens, and the first contains 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.

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, if 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 the second or the 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.

Bombay blood does not have antigens A and B, so it is often confused with the first group, but it also does not contain antigen H, which can become a problem, for example, when determining paternity - after all, the child does not have a single antigen in his blood that he has. him from his parents.

Bombay phenomenon was discovered in 1952 in India, where, according to statistics, 0.01% of the population have “special” blood; in Europe, Bombay blood is even less common - approximately 0.0001% of the population.

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

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How does it work (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 the residueN-acetyl-D-galactosamineto an agglutinogen, resulting in agglutinogen A).

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

Gene 0 does not code for any enzyme.

Inheritance of blood groups. Bombay phenomenon...

For example, let's cross parents with groups 1 and 4 and see why they havethere cannot be a child with 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.)

Inheritance of blood groups. Bombay phenomenon...

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.

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%).

Inheritance of blood groups. Bombay phenomenon...

An example of the Bombay phenomenon at work:if one parent has the first blood group, and the other has the second, then the child can't have fourth group, because none of them

parents do not have the B gene required for group 4.

Polymerism…

Polymerism is the interaction of non-allelic multiple genes that unidirectionally influence the development of the same trait; The degree of manifestation of a trait depends on the number of genes. Polymer genes are designated by the same letters, and alleles of the same locus have the same subscript.

Polymer interaction of non-allelic genes can be

cumulative and non-cumulative.

With cumulative (accumulative) polymerization, the degree of manifestation of the trait depends on the total action of several genes. The more dominant gene alleles, the more pronounced a particular trait is. Segregation in F2 according to the phenotype during dihybrid crossing occurs in the ratio 1: 4: 6: 4: 1, and in general corresponds to the third, fifth (with dihybrid crossing), seventh (with trihybrid crossing), etc. lines in Pascal's triangle.

Polymerism…

With non-cumulative polymerization, the signmanifests itself in the presence of at least one of the dominant alleles of polymer genes. The number of dominant alleles does not affect the degree of expression of the trait. Segregation in F2 according to phenotype during dihybrid crossing is 15:1.

Polymer example- inheritance of skin color in humans, which depends (to a first approximation) on four genes with a cumulative effect.

The human body is famous for its uniqueness. Due to various mutations that occur daily in our body, we become individual, since some of the characteristics that we acquire differ significantly from the same external and internal factors of other people. This also applies to blood type.

It is usually customary to divide it into 4 types. However, it is extremely rare, but it happens that a person who should have one (due to genetic characteristics parents) has a completely different, specific. This paradox is called the “Bombay phenomenon”.

What it is?

This term refers to a hereditary mutation. It is extremely rare - up to 1 case per ten million people. The Bombay phenomenon gets its name from the Indian city of Bombay.

In India, there is one settlement where people have a “chimeric” blood type quite often. This means that when determining erythrocyte antigens using standard methods, the result shows, for example, the second group, although in fact, due to a mutation in a person, the first.

This occurs due to the formation of a recessive pair of genes H in a person. Normally, if a person is heterozygous for this gene, then the trait does not appear; the recessive allele cannot perform its function. Due to the incorrect combination of parental chromosomes, a recessive pair of genes is formed, and the Bombay phenomenon occurs.

How does it develop?

History of the phenomenon

A similar phenomenon was described in many medical publications, but almost until the middle of the 20th century, no one had any idea why this was happening.

This paradox was discovered in India in 1952. The doctor, conducting a study, noticed that the parents had the same blood groups (the father had the first, and the mother the second), and the born child had the third.

Having become interested in this phenomenon, the doctor was able to determine that the father’s body had managed to somehow change, which made it possible to believe that he had the first group. The modification itself occurred due to the absence of an enzyme that allows the synthesis of the required protein, which would help determine the required antigen. However, since there was no enzyme, the group could not be determined correctly.

The phenomenon is quite rare among representatives. It is somewhat more common to find carriers of “Bombay blood” in India.

Theories of the origin of Bombay blood

One of the main theories for the emergence of a unique blood type is chromosomal mutation. For example, in a person with it is possible to recombine alleles on chromosomes. That is, during the formation of gametes, the genes responsible for can move as follows: genes A and B will end up in one gamete (the subsequent individual can receive any group except the first), and the other gamete will not carry the genes responsible for the blood type. In this case, inheritance of a gamete without antigens is possible.

The only obstacle to its spread is that many such gametes die without even entering embryogenesis. However, perhaps some survive, which subsequently contributes to the formation of Bombay blood.

It is also possible that gene distribution is disrupted at the zygote or embryonic stage (as a result of maternal malnutrition or excessive alcohol consumption).

The mechanism of development of this condition

As has been said, everything depends on genes.

A person’s genotype (the totality of all his genes) directly depends on the parent, or more precisely, on what characteristics were passed on from parents to children.

If you study the composition of antigens more deeply, you will notice that the blood type is inherited from both parents. For example, if one of them has the first, and the other has the second, then the child will have only one of these groups. If the Bombay phenomenon develops, everything happens a little differently:

• The second blood group is controlled by the gene a, which is responsible for the synthesis of a special antigen - A. The first, or zero, has no specific genes.
• The synthesis of antigen A is due to the action of the section of chromosome H responsible for differentiation.
• If there is a malfunction in the system of this section of DNA, then the antigens cannot differentiate correctly, which is why the child can acquire antigen A from the parent, and the second allele in the genotype pair cannot be determined (conventionally it is called nn). This recessive pair suppresses the action of area A, as a result of which the child has the first group.

If we generalize everything, it turns out that the main process causing the Bombay phenomenon is recessive epistasis.

Non-allelic interaction

As mentioned, the development of the Bombay phenomenon is based on non-allelic interaction of genes - epistasis. This type of inheritance is distinguished by the fact that one gene suppresses the action of another, even if the suppressed allele is dominant.

The genetic basis for the development of the Bombay phenomenon is epistasis. The peculiarity of this type of inheritance is that the recessive epistatic gene is stronger than the hypostatic gene, but it determines the blood group. Therefore, the inhibitor gene that causes suppression is not capable of producing any trait. Because of this, a child is born with “no” blood type.

This interaction is determined genetically, so it is possible to identify the presence of a recessive allele in one of the parents. It is impossible to influence the development of such a blood group, much less change it. Therefore, for those who have the Bombay phenomenon, the pattern of everyday life dictates some rules, following which, such people will be able to live normally and not fear for their health.

Features of life of people with this mutation

In general, people who carry Bombay blood are no different from ordinary people. However, problems arise when a transfusion is required (major surgery, accident or disease of the blood system). Due to the peculiarity of the antigenic composition of these people, they cannot be transfused with blood other than Bombay. Such errors are especially common in extreme situations when there is no time to thoroughly study the analysis of the patient’s red blood cells.

The test will show, for example, the second group. When a patient is transfused with blood of this group, intravascular hemolysis may develop, which will lead to death. It is precisely because of this incompatibility of antigens that the patient needs only Bombay blood, always with the same Rh as his.

Such people are forced to preserve their own blood from the age of 18, so that later they will have something to transfuse if necessary. There are no other features in the body of these people. Thus, we can say that the Bombay phenomenon is a “way of life” and not a disease. You can live with him, you just have to remember your “uniqueness.”

Paternity issues

The Bombay phenomenon is the “thunderstorm of marriage”. The main problem is that when determining paternity, it is impossible to prove the existence of the phenomenon without special research.

If suddenly someone decides to clarify the relationship, then they should definitely be informed that the presence of such a mutation is possible. The genetic match test in such a case should be carried out more extensively, with the study of the antigenic composition of blood and red blood cells. Otherwise, the child’s mother risks being left alone, without a husband.

This phenomenon can only be proven using genetic tests and determining the type of inheritance of blood group. The study is quite expensive and is not currently widely used. Therefore, when a child is born with a different blood type, one should immediately suspect the Bombay phenomenon. The task is not easy, since only a few dozen people know about it.

Bombay blood and its occurrence today

As has been said, people with Bombay blood are rare. This type of blood is practically never found in representatives of the Caucasian race; Among Indians, this blood is more common (on average, among Europeans, the occurrence of this blood is one case per 10 million people). There is a theory that this phenomenon develops due to the national and religious characteristics of the Hindus.

Everyone knows that it is a sacred animal and its meat cannot be eaten. Perhaps because beef contains some antigens that can cause changes, Bombay blood appears more often. Many Europeans eat beef, which serves as a prerequisite for the emergence of the theory of antigenic suppression of a recessive epistatic gene.

Possibly they influence climatic conditions, however, this theory is not currently being studied, so there is no evidence to substantiate it.

The significance of Bombay blood

Unfortunately, few people have heard about Bombay blood these days. This phenomenon is known only to hematologists and scientists working in the field genetic engineering. Only they know about the Bombay phenomenon, what it is, how it manifests itself and what needs to be done when it is identified. However, the exact cause of this phenomenon has not yet been identified.

If we look at it from an evolutionary point of view, Bombay blood is an unfavorable factor. Many people sometimes require a transfusion or replacement to survive. In the presence of Bombay blood, the difficulty lies in the impossibility of replacing it with blood of another type. Because of this, deaths often occur in such people.

If we look at the problem from the other side, it is possible that Bombay blood is more advanced than blood with a standard antigenic composition. Its properties have not been fully studied, so it is impossible to say what the Bombay phenomenon is - a curse or a gift.

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

Genetic principles

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

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

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 to contain (and, accordingly, not to transmit in generations) any information (0):

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

, can be clearly represented in the following examples:

• If parents have groups zero and four, their offspring can inherit only the second or third: AB + 00 = B0 or ​​A0.
• If both parents have group zero, then no other blood group can appear in the offspring: 00 + 00 = 00.
• For parents whose blood types are second and third, children have an equal chance of being born with any of the possible groups: AA/A0 + BB/B0 = AB, A0, B0, 00.

Currently, the existence of the so-called Bombay phenomenon, discovered by scientists in 1952, is known. Its essence lies in the fact that a person’s blood group is determined, which according to the laws of genetics is impossible, what is its explanation and the cause of the effect. That is, there is an agglutinogen on the membranes of his red blood cells, which neither of the parents has.

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

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

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

How often do such cases occur?

The prevalence of people with 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 increases to 0.01%. It was by the name of this city that this phenomenon was named (the old name was Bombay).

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

In Europe, such a ban does not exist and the frequency of manifestation of Bombay blood in humans here is several times lower. This led geneticists to the idea that beef contains specific antigens that suppress the manifestation of agglutinogens.

Specificity of people's lives

In reality, people with rare Bombay blood are no different from the rest. The only difficulty they may encounter is... Due to 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 used in case of emergency.

In the USA, in the state of Massachusetts, there are currently living a brother and sister who have the manifestation and essence of the Bombay phenomenon. Type them blood one akov, however, they cannot be donors for each other, since they have different Rh factors.

Problems of establishing paternity

When a child is born with manifestations of the Bombay phenomenon, it is impossible to prove its presence without the use of special methods for studying group affiliation. Therefore, the presence of Bombay blood in at least one of the family members (even the most distant relatives) should definitely be taken into account when the father has a desire to establish. Then specialists will conduct a test for genetic matches much more carefully and in a more extensive manner; in the process of studying samples of the genetic material of the father and child, the antigenic composition of the blood and the structure of the membranes of red blood cells will be studied.

Confirming the manifestation of the Bombay phenomenon in a child is possible only through the use of certain genetic tests that make it possible to establish the type of inheritance of blood group. For this reason, if a child is born with an unexpected blood type, first of all, one should suspect the manifestation of this unusual phenomenon in him, and not suspect the spouse of infidelity. This is the rarest blood group that can occur in humans, but it is extremely rare.

August 15th, 2017

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

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, if 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 the second or the 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 blood type 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 in the blood certain antigens. Antigens A and B are very common, making it easier to classify people based on which antigen they have, whereas people with type O blood have neither antigen. 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 may be present, and these antigens may react with the blood of certain donors. For example, someone may have blood type A+ and lack another antigen in their blood, indicating the likelihood of an adverse reaction with donated blood group A+ containing this antigen.

Bombay blood does not have antigens A and B, so it is often confused with the first group, but it also does not contain antigen H, which can become a problem, for example, when determining paternity - after all, the child does not have a single antigen in his blood that he has. him from his parents.

A rare blood type does not cause its owner any problems, except for one thing - if he suddenly needs a blood transfusion, then only the same Bombay blood can be used, 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 a family of patients, received an unexpected result: the father had blood group 1, the mother had blood group II, and the son had blood group 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 similar cases the body of one of the parents mimics (fake) one blood group, while in fact it has another; two genes are involved in the formation of a blood group: one determines the blood group, the second encodes the production of an enzyme that allows this group to be realized. This scheme works for most people, but in rare cases the second gene is missing, and therefore the enzyme is missing. Then the following picture is observed: a person has, for example. Blood group III, but it cannot be realized, and the analysis reveals II. Such a parent passes on his genes to the child - hence the “inexplicable” blood type in the child. There are few carriers of such mimicry - less than 1% of the Earth'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 less common - approximately 0.0001% of the population.

And now a little more detail:

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 of the H antigens into A antigens. (Gene A encodes a specific glycosyltransferase that adds an N-acetyl-D-galactosamine residue to an agglutinogen, resulting in agglutinogen A).

Gene B encodes an enzyme that converts some of the H antigens into B antigens (Gene B encodes a specific glycosyltransferase that adds a D-galactose residue to the 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 cannot 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 cannot have the fourth group, because neither parent 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.”

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; only the same blood can be used for these purposes, while it is a universal donor and is suitable for everyone;
· impossibility of establishing paternity; if it happens that DNA testing is necessary, 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 to each other, since they have a different Rh factor, and transfusion of any other group is, naturally, impossible. The eldest child reached adulthood and became a donor for himself as a last resort, the same fate awaits his younger sister when she turns 18