Determination of the origin and evolution of blood groups by methods of population genetics among various nationalities. Bombay Phenomenon: Discovery Story

We know from school that there are four main blood groups. The first three are common, while the fourth is rare. Classification of groups occurs according to the content of agglutinogens in the blood, which form antibodies. However, few people know that there is a fifth group, called the "Bombay Phenomenon".

To understand what is at stake, you should remember the content of antigens in the blood. So, the second group contains antigen A, the third - B, the fourth contains antigens A and B, and in the first group these elements are absent, but it contains antigen H - this is a substance that takes part in the construction of other antigens. In the fifth group there is neither A, nor B, nor H.

Inheritance

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

Discovery history

The discovery of an unusual blood group was made in 1952, in India, in the Bombay region. During malaria, mass blood tests were carried out. During the examinations, several people were identified whose blood does not belong to any of the four known groups, since it did not contain antigens. These cases have come to be known as the "Bombay Phenomenon". Later, information about such blood began to appear around the world, and in the world for every 250,000 people, one has a fifth group. In India, this figure is higher - one per 7,600 people.

According to scientists, the emergence of a new group in India is due to the fact that closely related marriages are allowed in this country. According to the laws of India, the continuation of the family within the caste allows you to save a position in society and family wealth.

What's next

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

The uniqueness of the 5th group

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

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

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

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

The Bombay Phenomenon (blood type V) is considered the newest, having been discovered decades ago. There are only 0.001% of people on the entire planet with such a group.

The formation of the phenomenon

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

laying chemical composition blood occurs still in utero and depends on the blood groups of the parents. And here, geneticists can say with what possible groups a baby can be born with simple calculations. Sometimes, nevertheless, deviations from the usual norm occur, and then children are born who show recessive epistasis (the Bombay phenomenon). There are no antigens A, B, H in their blood. This is the uniqueness of the fifth blood group.

People with the fifth group

These people live like millions of others, with other groups. Although they have some difficulties:

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

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

Biochemistry

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

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

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

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

Conclusion

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

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 group blood. 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. talking in simple words, under the influence of the mutation, the blood group 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 rare blood, when you get married, be sure to tell your spouse about it, 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

This article discusses the choice of medication for the treatment of hypertension in elderly patients. Older people suffering from hypertension are a category of patients to which doctors have a special relationship. Practice has shown that drug reduction blood pressure in older people has its own characteristics, and further you will find out what they are.

The standard approach used for patients between 30 and 60 years of age may not be effective for people retirement age. However, this in no way means that elderly hypertensive patients should give up on themselves, refusing any medical assistance. Effective treatment hypertension in the elderly is real! For this, the competent actions of the doctor, the vitality of the patient himself, as well as the support that his relatives can provide are important.

• The best way to cure hypertension (fast, easy, healthy, without "chemical" drugs and dietary supplements)
• Hypertonic disease - folk way recover from it at stages 1 and 2
• Causes of hypertension and how to eliminate them. Tests for hypertension
• Effective treatment of hypertension without drugs

If an elderly person suffering from hypertension does not have complications, it is recommended to start treatment with a thiazide diuretic, which is also prescribed for young people with a similar condition. However, an elderly person should start taking the drug with half the normal dose. For most older people, the optimal dosage is 12.5 mg dichlothiazide. It is necessary to increase the dosage to 50 mg in extremely rare cases. If 12.5 mg tablets are not available, break the 25 mg tablet into two halves.

Activity pharmacological agents to reduce blood pressure varies depending on the age of patients. This was confirmed in a 1991 study. In particular, it was possible to show that the effectiveness of thiazide diuretics is higher in persons 55 years of age and older than in younger patients. Therefore, diuretics in small doses are especially indicated for the treatment of elderly patients suffering from hypertension. Although older people often have high levels of cholesterol and other unhealthy blood fats (such as triglycerides), this does not necessarily preclude taking small doses of a thiazide diuretic (which raises blood cholesterol levels in high doses). It appears that taking a thiazide diuretic in low doses will have little effect on cholesterol levels.

If in the body low level potassium or sodium or high calcium levels, a thiazide diuretic may be taken in combination with a potassium-sparing drug. Supplemental potassium is not recommended for older people because at their age it causes two problems: it is difficult for them to take pills, and the kidneys can not cope with removing extra potassium from the body.

Calcium antagonists for the treatment of hypertension in the elderly

Calcium antagonists from the dihydropyridine subclass (nifedipine and its analogues), together with thiazide diuretics, are very suitable antihypertensive drugs for elderly patients. Dihydropyridine calcium antagonists are characterized by a moderate diuretic effect, which does not lead to a further decrease in the volume of circulating blood plasma, which is generally characteristic of old people and is usually enhanced by diuretics. Calcium antagonists are active in low-renin form of hypertension, support renal and cerebral blood flow. There are indications that drugs from this class can improve the properties of the aortic elastic chamber of the heart, thereby contributing to a decrease in systolic pressure, which is especially important for elderly patients.

Another study in 1998 confirmed the effectiveness of calcium antagonists in patients with isolated systolic hypertension. Patients were prescribed nitrendipine as monotherapy or in combination with enalapril or hypothiazide (12.5-25 mg per day). This made it possible to clearly reduce the risk of cardiovascular complications: sudden death - by 26%, stroke frequency - by 44%, total mortality - by 42%. There is no doubt that diuretics, as well as calcium antagonists, improve the prognosis for patients with isolated systolic hypertension. Calcium antagonists are not only drugs for pressure, but also effective means from angina. True, patients in whom hypertension is combined with ischemic disease heart, these drugs should not be taken for too long and better with breaks (pauses).

We would like to draw the attention of the readers of this article (this is for doctors, patients - do not self-medicate!) to the rather high efficacy of the calcium antagonist diltiazem in elderly patients with hypertension. Particularly good results can be obtained by combining diltiazem with perindopril. It is appropriate to consider another important issue. It has been suggested that calcium antagonists contribute to the development of cancer in patients over 65 years of age. In a large-scale study that lasted 3 years, these assumptions were not confirmed.

Treatment of hypertension in elderly patients with beta-blockers

If the patient cannot take a thiazide diuretic, or for some reason the drug is not suitable for the patient, it is recommended to take a beta-blocker. Beta-blockers are less effective than thiazide diuretics, and they also have more side effects.

Beta-blockers are less effective in treating older people with heart failure, asthma, chronic diseases lungs or obstructive vascular disease. However, if a person has previously taken a thiazide diuretic, but blood pressure has not returned to normal, additional intake of a beta-blocker often helps to normalize blood pressure.

Other drugs for the treatment of arterial hypertension in elderly patients

ACE inhibitors, angiotensin II receptor blockers are not as effective as thiazide diuretics or beta-blockers, but they can be used in cases where thiazide diuretics or beta-blockers are not suitable for any reason (for example, in case of drug allergy ). According to the results of the American study VACS (Veterans Affairs Study), the activity of captopril in patients 60 years of age and older did not exceed 54.5%. ACE inhibitors are more indicated for treatment in patients suffering from diabetes. The problem with ACE inhibitors and angiotensin II receptor blockers is that while they all lower blood pressure, they are less likely to prevent hypertension-related disease and death.

Joint reception ACE inhibitor and a diuretic may cause excessive lowering of blood pressure. A few days before you start taking an ACE inhibitor, you should stop taking the diuretic. The dose of an ACE inhibitor for an elderly person should be reduced. The usual daily dose is 10 mg, but the elderly should reduce this to 5 mg.

Other drugs that act on the brain are drugs such as methyldopa, clonidine (clopheline), and guanabenz, as well as alpha-adrenergic blockers. These are powerful drugs condition causing drowsiness and depression, as well as a decrease in blood pressure when standing. Elderly people are prescribed with caution. Alpha-1-blockers (doxazazine, etc.) remain the drugs of choice for the treatment of hypertension in patients suffering from benign prostatic hyperplasia (adenoma). Agonists of the central alpha-2-adrenergic receptors (clophelin) cause weakness, drowsiness, and mental depression in elderly patients with hypertension. In addition, the treatment with clonidine (clopheline) often causes "rebound" hypertension and, apparently, there is no reverse development of left ventricular hypertrophy of the heart.

Special cases

• The use of beta-blockers is advisable in cases where an elderly hypertensive person also has chest pain caused by coronary atherosclerosis.
• ACE inhibitors tend to prolong life for people with congestive heart failure, so these are the drugs that should be given to people in the event of a heart attack and hypertension.
• ACE inhibitors and angiotensin II receptor blockers are especially useful for older people with elevated blood pressure who have kidney problems, often associated with diabetes.

Which antihypertensive drugs should be used in elderly patients, depending on the presence of comorbidities

This information is provided for physicians! Patients - please do not prescribe hypertension pills yourself! Contact a qualified doctor!

• How to properly take antihypertensive medication for an elderly person
• Isolated systolic hypertension in the elderly
• Pseudohypertension in the elderly
• Postural hypertension in the elderly

Hematocrit increased or decreased: what does it mean and why does it happen

The norm in children and adult men and women

You can find out about hematocrit indicators after passing general analysis blood (displayed as a percentage by the HBT indicator). Healthy condition organism depends on the patient's age and sex.

Age group - children:

• newborns - 35-65
• up to 12 months - 32-40
• from one to eleven years - 32-41

Teenagers (12-17 years old):

• girls - 35-45
• boys - 34-44

Age group - adults:

• women from 18 to 45 - 39-50
• men from 18 to 45 years old - 34-45
• age of a man over 45 - 40-50
• woman's age over 45 - 35-46

Concentration variations in hematocrit in adults between 30% and 35% will require observation in the clinic and recommendations for dietary changes to increase the consumption of meat, liver, fruits and leafy vegetables.

29% and 24% - a pre-morbid condition, eliminated by taking drugs with iron, vitamin B and folic acid.

Elevated hematocrit

High hematocrit concentrations result in more thick blood which increases the risk of thrombosis. An increase in hematocrit in the blood can occur due to an unhealthy lifestyle and for other reasons:

• Dehydration. The use of liquid less than the norm leads to a deficiency of moisture, respectively, reduced plasma concentrations change blood counts. Active dehydration is manifested after diarrhea, bouts of vomiting, overheating, too active physical exercises that provoked profuse sweating.
• Hypoxia. Chronic lack of oxygen leads to the active appearance of new blood cells- erythrocytes, which serve to transport oxygen to the tissues of various organs. Hypoxia is typical for people who have been in stuffy spaces for a long time, smokers and patients with diabetes.
• mountain conditions. Directly related to hypoxia caused by being in a mountainous area. The low oxygen content in rarefied air leads to an unpleasant effect - increased production of red blood cells. Climbers and people who are forced by the profession to be at a height are advised to take oxygen cartridges with them.

Indicator in the diagnosis of cardiovascular diseases

Bringing the number of red blood cells in the blood to normal is extremely important for the "cores".

Blockage of the lumen of the vessels, the formation of blood clots in small and large arteries impede the arterial flow, dangerously loading the heart muscle. A weak heart begins to work for wear and tear, which leads to an increased risk of myocardial infarction.

Formed arterial thromboses (due to an increase in the number of platelets) initially lead to the appearance of an ischemia stage, followed by a process of tissue death through induced oxygen starvation.

Heart failure, which results in fluid accumulation, also results in identical test results. The critical content of hematocrit is considered to be more than 50-55% (hospitalization is required).

Significance of a high level in the definition of other diseases

Kidney problems, primarily hydronephrosis and polycystic, lead to an increase in the quantitative value of red blood cells. A similar effect is given by uncontrolled (long-term) use of corticosteroid and diuretic drugs that stimulate the removal of fluid from the body.

Other states:

• transferred stress;
• injury skin(over 10%);
• diseases of the gastrointestinal tract;
• erythrocytosis;
• bone marrow disease.

Pulmonary diseases - bronchial asthma, obstructive bronchitis- make it difficult to supply oxygen to the lungs, so the process of hematopoiesis is enhanced.

During pregnancy, late toxicosis disrupts the functioning of the kidneys, which increases the content of red blood cells in the blood. Thickening of the blood is observed closer to childbirth - in the second half of pregnancy: this is how nature prepares a woman for childbirth, often associated with abundant blood loss.

Reduced content

Red blood cells are involved in the construction of the body, nourishing it with amino acids and carrying out gas exchange. A decrease in the number of blood cells can lead to various dysfunctions and problematic conditions. Reduced level should alert. Consider possible reasons decrease in hematocrit in the blood.

Cardiac pathologies

Any heart disease is more difficult to treat with a decrease in the number of red blood cells, since cardiac problems are exacerbated by the obstructed supply of oxygen to the tissues of the heart. In contrast to elevated hematocrit, reduced content erythrocytes does not have such a detrimental effect on the heart.

The ratio of erythrocytes and hemoglobin:

• initial stage - 3.9-3 / 110-89
• medium - 3-2.5 / 89-50
• severe - less than 1.5 / less than 40

These indicators also determine the degree of anemia.

Low interest for other reasons

A reduced number of red blood cells is often associated with general malaise, a constant desire to lie down to rest, and a general breakdown. The most common ailment when the hematocrit in the blood is reduced is anemia caused by a decrease in the amount of iron.

Causes of a decrease in red blood cells:

• blood loss;
• hyperhydration;
• primary tumors;
• dysbacteriosis;
• smoking and alcohol.

Long-term use of medications can also cause blood thinning, for example, frequent use of aspirin leads to just such a consequence.

An unfavorable factor is prolonged bed rest, as well as high water intake (also called kidney failure and intravenous infusions).

Transferred infectious diseases and chronic inflammatory processes equally have a lowering effect on the number of red elements in the blood. Dangerous are not only visible - caused by fractures and injuries - bleeding, but also hidden, primarily internal.

Cirrhosis of the liver, disintegration of tumors, uterine fibroma, varicose veins veins of the esophagus, thallasemia are frequent companions of invisible blood loss.

Children's tests - what to prepare for

Newborns often show hyperprolactinemia, indicating an increase in protein in the blood plasma. It is caused by feeding the child with goat or cow milk (situation: mom is not available breast-feeding) high in protein. To increase the tendency to thicken the blood, you should buy milk with a lower protein content.

Over the age of 3 years, there is a decrease in mental abilities, fatigue, shortness of breath, pale skin color and rapid heartbeat. Among diseases in children there are all diseases characteristic of this group, however, unpleasant conditions are also caused by a trivial vitamin deficiency.

Worm infection, which is more typical for children and adolescents than for adults, must be eliminated by taking anthelmintic drugs, after a course of which the tests return to normal.

Changes in the blood during pregnancy

A woman who is in a state of bearing a baby experiences a natural increase in the amount of blood, due to which the hematocrit decreases slightly.

After birth, all indicators return to normal, otherwise, unsatisfactory test results are corrected by taking iron-containing drugs.

Extremely low rates lead to malaise and the likelihood of developing anemia. Red blood cell concentrations of less than 30% are dangerous for the unborn baby, as the fetus begins to experience oxygen starvation.

Summing up

Now you know what it means and what the situation leads to when the hematocrit is above or below normal. There are a few basic facts to keep in mind:

• In children, a change in the number of red blood cells is a frequent physiological norm.
• In newborns, the ratio of elements in the blood is significantly higher than in adults.
• In men, the hematocrit value is higher than in women.
• A long-term decrease in red blood cells requires a consultation with a hematologist.
• Hematocrit less than 13% requires urgent hospitalization.

Be attentive to your health! More interesting on the topic is told in the video:

) 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, because in case of an emergency need to receive necessary material will be virtually non-existent.

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 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 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.”