Bombay blood. What blood type is the rarest

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.

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.

The Bombay phenomenon was discovered in 1952 in India, where, according to statistics, 0.01% of the population has “special” blood, in Europe Bombay blood is even rarer - about 0.0001% of the inhabitants.

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.

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) is a type of non-allelic interaction (recessive epistasis) of the gene h with genes responsible for the synthesis of AB0 blood group agglutinogens on the surface of erythrocytes. For the first time this phenotype was discovered by Dr. Bhende (Y. M. Bhende) in 1952 in the Indian city of Bombay, which 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 usually determine whether blood belongs to one or another group. There is an assumption that the occurrence of such a phenomenon is associated with frequent closely related marriages, which are traditional in this part of the globe. Perhaps for this reason, in India, the number of people with this type of blood is 1 case per 7,600 people, with an average for the world's population of 1:250,000.

Description

In people who have this gene in a state of recessive homozygous hh, agglutinogens are not synthesized on the erythrocyte membrane. Accordingly, agglutinogens are not formed on such erythrocytes. A and B because there is no basis for their education. This leads to the fact that carriers of this type of blood 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 transfuse the blood of people with the same "phenomenon".

Spreading

The number of people with this phenotype is approximately 0.0004% of the total population, however, in some areas, in particular, in Mumbai (the former name is Bombay), their number is 0.01%. Given the exceptional rarity of this type of blood, its carriers are forced to create their own blood bank, since in case of an emergency transfusion, there will be practically no place to get the necessary material.

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 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 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 type 4 blood, 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 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.”

A person with a blood type known as the Bombay phenomenon is a universal donor: his blood can be transfused to people with any blood type. However, people with this rarest blood type cannot accept any other type of blood. Why?

There are four blood groups (first, second, third and fourth): the classification of blood groups is based on the presence or absence of an antigenic substance that appears on the surface of blood cells. Both parents influence and determine the child's blood type.

Knowing the blood type, a couple can predict the blood type of their unborn child using the Pannet lattice. For example, if the mother has a third blood type and the father has a first blood type, then most likely their child will have a first blood type.

However, there are rare cases when a couple has a child with the first blood group, even if they do not have the genes of the first blood type. If so, the child most likely has the Bombay Phenomenon, which was first discovered in three people in Bombay (now Mumbai) in India in 1952 by Dr. Bhende and his colleagues. Main characteristic erythrocytes in the Bombay phenomenon is the absence of h-antigen in them.

Rare blood type

h-antigen is located on the surface of erythrocytes and is a precursor of antigens A and B. The A-allele is necessary for the production of transferase enzymes that convert h-antigen into A-antigen. In the same way, the B allele is required for the production of transferase enzymes for the conversion of the h antigen to the B antigen. In the first blood type, the h-antigen cannot be converted because transferase enzymes are not produced. It should be noted that the transformation of the antigen occurs by adding complex carbohydrates produced by transferase enzymes to the h-antigen.

Bombay Phenomenon

A person with Bombay phenomenon inherits a recessive allele for the h antigen from each parent. It carries a homozygous recessive (hh) genotype instead of the homozygous dominant (HH) and heterozygous (Hh) genotypes found in all four blood groups. As a result, the h-antigen does not appear on the surface of blood cells, so the A and B antigens are not formed. The h-allele is the result of a mutation of the H-gene (FUT1), which affects the expression of the h-antigen in red blood cells. The scientists found that people with the Bombay Phenomenon are homozygous (hh) for the T725G mutation (leucine 242 changes to arginine) in the FUT1 coding region. As a result of this mutation, an inactivated enzyme is produced that is unable to form the h-antigen.

Antibody production

People with the Bombay phenomenon develop protective antibodies against the H, A, and B antigens. Because their blood produces antibodies against the H, A, and B antigens, they can only receive blood from donors with the same phenomenon. Blood transfusion of the other four groups can be fatal. In the past, there have been cases where patients with supposedly type I blood died in transfusions because doctors did not test for the Bombay Phenomenon.

Since the Bombay phenomenon is, it is very difficult for patients with this blood type to find donors. The chance of a donor with the Bombay phenomenon is 1 in 250,000 people. India has the most people with the Bombay phenomenon: 1 in 7600 people. Geneticists are convinced that a large number of people with the Bombay phenomenon in India are due to consanguineous marriages between members of the same caste. A one-blood marriage in a higher caste allows you to maintain your position in society and protect wealth.

If the child's blood type does not match one of the parents, this can be a real family tragedy, as the baby's father will suspect that the baby is not his own. In fact, such a phenomenon may be due to a rare genetic mutation that occurs in the European race in one person in 10 million! In science, this phenomenon is called the Bombay Phenomenon. In biology class, we were taught that a child inherits the blood type of one of the parents, but it turns out that this is not always the case. It happens that, for example, parents with the first and second blood groups, a baby is born with the third or fourth. How is this possible?

For the first time, genetics encountered a situation when a baby had a blood type that could not be inherited from its parents in 1952. The male father had I blood type, the female mother had II, and their child was born with III blood group. According to this combination is not possible. The doctor who observed the couple suggested that the father of the child did not have the first blood type, but its imitation, which arose due to some kind of genetic changes. That is, the gene structure has changed, and therefore the signs of blood.

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 erythrocyte membrane. Inherited from parents, these antigens create a combination that determines one of four groups blood.

At the heart of the Bombay phenomenon is recessive epistasis. In simple terms, under the influence of a mutation, the blood type has signs of I (0), since it does not contain agglutinogens, but in fact it is not.

How can you tell if you have the Bombay Phenomenon? Unlike the first blood group, when there are no 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. Although there will be no agglutinogen B on the child's erythrocytes (reminiscent of I (0) 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 group I have both agglutinins - A and B.

When a blood transfusion becomes necessary, patients with the Bombay Phenomenon should only be transfused with exactly the same blood. Finding it, for obvious reasons, is unrealistic, so people with this phenomenon, as a rule, save their own material at blood transfusion stations in order to use it if necessary.

If you are the owner of such a rare blood, be sure to tell your spouse about it when you get married, and when you decide to have offspring, consult a geneticist. In most cases, people with the Bombay phenomenon give birth to children with the usual blood type, but not according to the rules of inheritance recognized by science.

Photos from open sources

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 the four blood groups.

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 the 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.

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.)

The A gene codes for 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 to form agglutinogen A).

The B gene codes for 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 an agglutinogen to form 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 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 the Bombay Phenomenon #1 at work: if one parent has the first blood type, and the other has the second, then the child has the fourth group, because none of the parents has the B gene necessary for group 4.

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.”

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.)

The A gene codes for an enzyme that converts some of the H antigens into A antigens.(Gene A encodes a specific glycosyltransferase that adds a residueN-acetyl-D-galactosamineto an agglutinogen, resulting in agglutinogen A).

The B gene codes for an enzyme that converts some of the H antigens into B antigens.. (Gene B encodes a specific glycosyltransferase that adds a residue D-galactose to agglutinogen to form agglutinogen B).

Gene 0 does not code for any enzyme.

Inheritance of blood groups. Bombay Phenomenon...

For example, we cross parents with groups 1 and 4 and see why they havethere can't be a child with 1

(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.)

Inheritance of blood groups. Bombay Phenomenon...

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.

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%).

Inheritance of blood groups. Bombay Phenomenon...

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

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

Polymerism…

Polymeria - the interaction of non-allelic multiple genes that unidirectionally affect the development of the same trait; the degree of manifestation of a trait depends on the number of genes. Polymeric genes are denoted 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 a trait depends on the total action of several genes. The more dominant alleles of genes, the more pronounced this or that trait. Splitting in F2 by phenotype during dihybrid crossing occurs in the ratio 1:4:6:4:1, and in general corresponds to the third, fifth (during dihybrid crossing), seventh (during trihybrid crossing), etc. lines in Pascal's triangle.

Polymerism…

With non-cumulative polymer, the signmanifests itself in the presence of at least one of the dominant alleles of polymeric genes. The number of dominant alleles does not affect the severity of the trait. Splitting in F2 by phenotype in dihybrid crossing - 15:1.

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