The human body is famous for its uniqueness. Due to the various mutations that occur daily in our body, we become individual, since some of the signs that we acquire differ significantly from the same external and internal factors of other people. This also applies to blood types.
It is usually accepted to subdivide it into 4 types. However, it is extremely rare, but it occurs that a person who should have one blood type (due to the genetic characteristics of the parents) has a completely different, specific one. This paradox is called the “Bombay phenomenon.”
What is this?
This term is understood as a hereditary mutation. It is extremely rare - up to 1 case per ten million people. The Bombay phenomenon takes its name from the Indian city of Bombay.
In India, there is one settlement, in whose people the “chimeric” blood type is quite common. This means that when determining erythrocyte antigens by standard methods, the result shows, for example, the second group, although in fact, due to a mutation in a person, the first.
This is due to the formation of a recessive pair of H genes in humans. It is normal ifa 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 takes place.
How does it develop?
History of the phenomenon
This 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 types (the father had the first, and the mother had the second), and the born child had the third.
Being interested in this phenomenon, the doctor was able to determine that the body of the father managed to somehow change, which made it possible to assume that he had the first group. The modification itself occurred due to the lack of an enzyme that allows the synthesis of the desired protein, which would help determine the necessary antigen. However, if there was no enzyme, then the group could not be determined correctly.
The phenomenon among representatives of the Caucasian race is quite rare. Somewhat more often you can find carriers of "Bombay blood" in India.
Theory of Bombay blood
One of the main theories for the emergence of a unique blood group is a chromosomal mutation. For example, in a person with a fourth blood group, recombination of alleles on chromosomes is possible. That is, during the formation of gametes, the genes responsiblefor inheriting a blood type, can move as follows: genes A and B will be in the same gamete (a 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, the inheritance of the gamete without antigens is possible.
The only obstacle to its spread is that many of these gametes die without even entering embryogenesis. However, it is possible that some survive, which subsequently contributes to the formation of Bombay blood.
Perhaps a violation of the gene distribution at the stage of the zygote or embryo (as a result of maternal malnutrition or excessive alcohol consumption).
Mechanism for the development of this state
As said, it all depends on the genes.
A person's genotype (the totality of all his genes) directly depends on the parent, more precisely, on what traits passed 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, things happen a little differently:
- The second blood type 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 part of the chromosome H responsible for differentiation.
- If there is a failure in the system of this DNA section,then the antigens cannot differentiate correctly, which is why the child can acquire antigen A from the parent, and the second allele in the genotypic pair cannot be determined (conditionally it is called nn). This recessive pair suppresses the action of site A, as a result of which the child has the first group.
To summarize, it turns out that the main process that causes the Bombay phenomenon is recessive epistasis.
Non-allelic interaction
As it was said, the development of the Bombay phenomenon is based on non-allelic interaction of genes - epistasis. This type of inheritance is different in 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 one, but which determines the blood group. Therefore, an inhibitor gene causing suppression is incapable of producing any trait. Because of this, a child is born with “no” blood type.
Such an interaction is genetically determined, so it is possible to detect the presence of a recessive allele in one of the parents. It is impossible to influence the development of such a blood group, and even more so to change it. Therefore, for those who have the Bombay phenomenon, the pattern of everyday life dictates some rules, following which, such people can live a normal life and not be afraid for their he alth.
Features of life of people with this mutation
In general people-carriers of Bombay blood are no different from ordinary ones. 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. Especially often such errors occur in extreme situations, when there is no time to thoroughly study the analysis of the patient's erythrocytes.
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 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 conserve their own blood from the age of 18, so that later they have something to transfuse if necessary. There are no other features in the body of these people. Thus, it can be said that the Bombay phenomenon is a “way of life” and not a disease. You can live with him, you just need to remember your “uniqueness”.
Problems with fatherhood
The Bombay Phenomenon is the “thunderstorm of marriage”. The main problem is that when determining paternity without special studies, it is impossible to prove the existence of the phenomenon.
If suddenly someone decides to clarify the relationship, then be sure to inform him that the presence of such a mutation is possible. The test for genetic matching in such a case should be carried out more extensively, with the study of the antigenic composition of the blood anderythrocytes. Otherwise, the child's mother runs the risk of being left alone, without her husband.
This phenomenon can only be proved with the help of genetic tests and determining the type of inheritance of the blood type. The study is quite expensive and not currently widely used. Therefore, at the birth of a child with a different blood type, the Bombay phenomenon should be immediately suspected. The task is not easy, as only a few dozen people know about it.
Bombay blood and its current occurrence
As said, people with Bombay blood are rare. In representatives of the Caucasian race, this type of blood practically does not occur; among Hindus, this blood is more common (on average, in Europeans, the occurrence of this blood is one case per 10 million people). There is a theory that this phenomenon is developing due to the national and religious characteristics of the Hindus.
Everyone knows that in India the cow is a sacred animal and its meat should not be eaten. Perhaps because beef contains certain antigens that can cause a change in the genetic code, Bombay blood is more likely to show up. Many Europeans eat beef meat, which is a prerequisite for the emergence of the theory of antigenic suppression of the recessive epistatic gene.
Climatic conditions may also have an effect, but this theory is currently not being studied, so the evidence for itno justification.
The Importance of Bombay Blood
Unfortunately, not many people have heard of Bombay blood these days. This phenomenon is known only to hematologists and scientists working in the field of 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 detected. However, the exact cause of this phenomenon has not yet been identified.
From the point of view of evolution, Bombay blood is an unfavorable factor. Many people sometimes need a transfusion or replacement to survive. In the presence of Bombay blood, the difficulty lies in the impossibility of replacing it with another type of blood. Because of this, deaths often develop in such people.
If you look at the problem from the other side, it is possible that Bombay blood is more perfect than blood with a standard antigenic composition. Its properties are not fully understood, so it cannot be said whether the Bombay phenomenon is a curse or a gift.
