10.04.2015 13.10.2015
Blood is a unique fluid in the human body, it continuously circulates through the vessels, nourishes with oxygen, as well as with the necessary components of the internal organs. Everyone knows that there are four of its groups, I, II, III, IV, but not everyone knows about the existence of another, extremely rare, exceptional group, called the Bombay phenomenon.
Uncharted blood, discovery story
The discovery of the phenomenon took place in 1952, in India (the city of Mumbai, formerly Bombay, where the name came from), by the scientist Bhende. The discovery was made during research on mass malaria, after three people lacked the necessary antigens that determine which type the blood belongs to. The cases of occurrence are unique, the number of people with the Bombay phenomenon in the world is one per two hundred and fifty thousand people, only in India this figure is higher, it is 1 case per 7600 people.
Interesting fact! Scientists believe that the emergence of unknown blood in India is associated with frequent marriages with members of their own family. According to the laws of the country, the continuation of the family in the circle of one, the highest caste, allows you to save wealth and your position in society.
Recently, a sensational statement was made by employees of the University of Vermont that there are still types of the rarest blood, their names are Junior and Langeris. They were discovered by mass spectrometry, as a result of which two completely new proteins were identified, previously science knew about 30 proteins responsible for the blood type, and now there are 32 of them, which allowed scientists to announce their discovery. Experts believe that this discovery is a new step in the fight against cancer and will allow the development of a new technology for the treatment of oncology.
What is the uniqueness?
The first group is considered the most common, it arose during the time of the Neanderthals and has been known for more than 40 thousand years, almost half of its carriers on earth;
The second has been known for more than 15 thousand years, it is also not rare, according to various sources, about 35% of its carriers, more than all people with this species in Japan and Western Europe;
the third, slightly less common than the first two, about the same is known about it as about the second, the largest concentration of people with this species is found in Eastern Europe, in total its carriers are about 15%;
The fourth, the newest, no more than a thousand years have passed since its formation, it arose as a result of the merger of I and III, only in 5%, and according to some data, even in 3% of the world's population, this important red liquid flows through the vessels.
Now imagine if the IV group is considered young and rare, what can we say about the Bombay, which is just over 60 years old from the moment of discovery and is found in 0.001% of people on the planet, of course, its uniqueness is undeniable.
How is the phenomenon formed?
The classification into groups is based on the content of antigens, for example, the second contains antigen A, the third - B, the fourth contains both of them, and in the first they are absent, but there is the original antigen H and all the rest arise from it, it is considered a kind of "building material" for A and B.
The laying of the chemical composition of the blood in a child occurs even in utero and depends on what it is in the parents, it is heredity that becomes the fundamental factor. But there are rare exceptions to the rule that defy genetic explanation. This is the emergence of the Bombay phenomenon, it lies in the fact that born children have the kind of blood that a priori they cannot have. It does not have A and B antigens, so it can be confused with the first group, but it also does not have the H component, this is its uniqueness.
How do they live with unusual blood?
The everyday life of a person with unique blood does not differ from its other classifications, with the exception of several factors:
· transfusion is a serious problem, only the same blood can be used for these purposes, while it is a universal donor and suitable for everyone;
Impossibility to establish paternity, if it happened that it is necessary to make DNA, it will not give results, since the child does not have the antigens that his parents have.
Interesting fact! In the USA, Massachusetts, there lives a family where two children have the Bombay phenomenon, only at the same time they also have the A-H type, such blood was diagnosed once in the Czech Republic in 1961. They cannot be donors for each other, since they have a different Rh- factor, and the transfusion of any other group, of course, is impossible. The eldest child has reached the age of majority and became a donor for himself in case of emergency, such a fate awaits his younger sister when she turns 18 years old.
In the body of an average adult male, the volume of blood is 5-6 liters;
· The fourteenth of June is considered the World Donor Day, it is timed to coincide with the birthday of Karl Landsteiner, he first classified blood into groups;
· It is believed that if the icon began to bleed - to be in trouble, there are people who claim to have observed this process before the September 11, 2001 terrorist attack and the start of World War II. Written sources also speak of a bleeding icon before Bartholomew's night;
In the middle of the 20th century, a relationship was established between the tendency to certain diseases and the blood type, for example, the owners of the second group are more susceptible to leukemia and malaria, from the first - to torn ligaments, tendons and peptic ulcers;
The diagnosis of cancer is heard most often by people with the third group, less often than others with the first;
There is a person who lives without a pulse, his uniqueness lies in the fact that instead of the heart that he was removed, he has a device for blood circulation, it continues to function in full, but there is no pulse even when an ECG is performed;
· In Japan, they are confident that the character and fate of a person depends on what kind of blood he was born with.
A lot of mysteries and secrets are stored in the liquid that has evolved for millions of years in order to give us the opportunity to live. It protects us from environmental influences, from various viruses and infections, neutralizing them, preventing them from penetrating into vital organs. But how many more secrets, in addition to the Bombay phenomenon, as well as the groups of Junior and Langeris, scientists have to reveal and tell the whole world.
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 types (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. The main characteristic of erythrocytes in the Bombay phenomenon is the absence of the 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 is worth noting 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 A and B antigens are not formed. The h-allele is the result of a mutation in 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 the four blood groups.
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 precursors of agglutinogens, 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 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. 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 in the early stages of 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:
| genes | Group |
| 00 | 1 |
| 0A | 2 |
| AA | |
| 0V | 3 |
| BB | |
| AB | 4 |
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:
| genes | specific antigens on the surface of red blood cells | blood type | group letter |
| 00 | - | 1 | 0 |
| A0 | BUT | 2 | BUT |
| AA | |||
| B0 | IN | 3 | IN |
| BB | |||
| AB | A and B | 4 | AB |
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.
| Parent AB (Group 4) |
Parent AB (Group 4) | |
| BUT | IN | |
| BUT | AA (Group 2) |
AB (Group 4) |
| IN | AB (Group 4) |
BB (group 3) |
And now the Bombay Phenomenon
| Parent ABHh (Group 4) |
Parent ABHh (Group 4) | |||
| AH | Ah | BH | bh | |
| AH | AAHH (Group 2) |
AAHh (Group 2) |
ABHH (Group 4) |
ABHh (Group 4) |
| Ah | AAHH (Group 2) |
Ahh (1 group) |
ABHh (Group 4) |
ABhh (1 group) |
| BH | ABHH (Group 4) |
ABHh (Group 4) |
BBHH (group 3) |
BBHh (group 3) |
| bh | ABHh (Group 4) |
ABhh (1 group) |
ABHh (Group 4) |
BBhh (1 group) |
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.
| What other parents can offer | mutant parent | |
| AB | - | |
| 0 | AB0 (Group 4) |
0- (1 group) |
| BUT | AAB (Group 4) |
BUT- (Group 2) |
| IN | ABB (Group 4) |
IN- (group 3) |
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:
| Parent 00 (1 group) | AB mutant parent (Group 4) |
|||
| AB | - | BUT | IN | |
| 0 | AB0 (Group 4) |
0- (1 group) |
A0 (Group 2) |
B0 (group 3) |
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.”
Today, every person is aware of the existing division of known blood groups according to the AB0 system. In biology lessons, they talk in some detail about the principles, about compatibility, about the prevalence among the population of each type. So, it is generally accepted that the rarest blood type is the fourth, and the rarest Rh factor is negative. In fact, such information is not true.
genetic principles
Based on the data obtained in the field of archeology and paleontology, geneticists were able to determine that the first division into occurred more than 40 thousand years ago. It was then, according to scientists, that arose. Later, over the course of millennia, as a result of certain mutational changes, the rest of its currently known types arose.
The group affiliation of human blood according to the AB0 system is determined by the presence or absence of unique compounds on the erythrocyte membranes - agglutinogens (antigens) A and B.
The blood type is inherited according to the laws of genetics and is determined by two genes, one of which is passed on to the child by the mother, and the second by the father. Each of these genes is programmed at the DNA level to transmit only one of these agglutinogens or not contain (and therefore not transmit in a generation) any information (0):
- first 0(I) -00;
- A(II) - A0 or AA;
- B(III) - B0 or BB;
- AB (IV) - AB.
, can be seen in the following examples:
- If the parents have zero and fourth groups, their offspring can inherit only the second or third: AB + 00 = B0 or A0.
- If both parents have a zero group, then no other blood type can occur in the offspring: 00 + 00 = 00.
- Parents whose blood types are second and third have equal chances of being born with any of the possible blood groups: AA / A0 + BB / B0 \u003d AB, A0, B0, 00.
At present, the existence of the so-called Bombay phenomenon, discovered by scientists in 1952, is known. Its essence lies in the fact that a person determines the group affiliation of blood, which, according to the laws of genetics, is impossible, what is its explanation and the cause of the effect. That is, on the membranes of his erythrocytes there is an agglutinogen, which none of the parents has.
An example of the Bombay phenomenon, the rarest blood type:
- For parents with a zero group, a child is born with a third: 00 + 00 = B0.
- For parents whose groups are zero and , the child is born with the fourth or second: 00 + B0 / BB \u003d AB, A0.
After numerous studies, an explanation of the Bombay phenomenon was obtained. The answer is that in extremely rare cases, when determining the blood type by standard methods (according to the AB0 system) as zero 0 (I), in fact it is not. In fact, one of the agglutinogens, either A or B, is present on the membranes of her erythrocytes, but under the influence of specific factors, they are suppressed and when determining the group, the blood behaves like 0 (I). But when suppressed agglutinogen is inherited in children, it manifests itself. As a result, parents have doubts about the existence of kinship between them and the child.
How often do such cases occur?
The prevalence of people with the Bombay blood phenomenon in the world does not exceed 0.0004% of all people on the globe. The exception is the Indian city of Mumbai, where the frequency percentage rises to 0.01%. It was by the name of this city that this phenomenon was named (the old name is Bombay).
One of the theories that studies the causes and factors influencing the manifestation of this phenomenon in the population says that in Hindus a higher incidence of this type of blood is due to religious characteristics, in particular, the prohibition of eating beef meat.
In Europe, there is no such ban, and the frequency of manifestation of Bombay blood in humans is several times less here. This led genetic scientists to the idea that beef contains specific antigens that suppress the manifestation of agglutinogens.
The specificity of people's lives
In reality, people with rare Bombay blood are no different from the rest. The only difficulty they may face is . Because of the uniqueness of the blood type, they cannot be transfused with any foreign blood, since Bombay blood in humans is incompatible with all other groups. Therefore, people who exhibit this phenomenon are forced to create their own blood bank, which will be activated in case of emergency.
In the United States in the state of Massachusetts today there are brother and sister who have the manifestation and essence of the Bombay phenomenon. Their blood type is the same, but they cannot be donors for each other because they have different Rh factors.
Problems of establishing paternity
At the birth of a child with manifestations of the Bombay phenomenon, it is impossible to prove its presence without the use of special methods for studying group membership. Therefore, the presence of Bombay blood in at least one of the family members (even the most distant relatives) must be taken into account when the father has a desire to establish. Then the test for genetic matches will be carried out by specialists much more thoroughly and more extensively, in the process of examining samples of the genetic material of the father and child, the antigenic composition of the blood and the structure of erythrocyte membranes will be studied.
It is possible to confirm the manifestation of the Bombay phenomenon in a child only through the use of certain genetic tests that allow to establish the type of inheritance of the blood group. For this reason, if a child is born with an unexpected blood type, in the first place, one should suspect that he has this unusual phenomenon, and not suspect the spouse of infidelity. This is the rarest blood type in a person, but it is extremely rare.
Task 1
When crossing plants of one of the pumpkin varieties with white and yellow fruits, all F 1 offspring had white fruits. When these offspring were crossed with each other in their offspring F 2, the following was obtained:
207 plants with white fruits,
54 plants with yellow fruits,
18 plants with green fruits.
Determine possible genotypes of parents and offspring.
Solution:
1.
The cleavage 204:53:17 corresponds approximately to a ratio of 12:3:1, which indicates the phenomenon of epistatic gene interaction (when one dominant gene, for example A, dominates over another dominant gene, for example B). Hence, the white color of the fruit is determined by the presence of the dominant gene A or the presence of two AB alleles in the genotype of the dominant genes; the yellow color of the fruit is determined by the B gene, and the green color of the fruit by the aavb genotype. Therefore, the original plant with yellow fruits had the aaBB genotype, and the white-fruited one had the AAbb genotype. When they were crossed, the hybrid plants had the AaBv genotype (white fruits).
First cross scheme:
2.
During self-pollination of plants with white fruits, 9 white-fruited plants (genotype A! B!),
3 - white-bearing (genotype A!vv),
3 - yellow-fruited (genotype aaB!),
1 - green-fruited (genotype aavb).
The ratio of phenotypes is 12:3:1. This corresponds to the conditions of the problem.
Second cross scheme:
Answer:
Parental genotypes are AABB and aabb; F1 offspring are AaBb.
Task 2
In Leghorn chickens, the color of feathers is due to the presence of the dominant gene A. If it is in a recessive state, then the color does not develop. The action of this gene is influenced by gene B, which in the dominant state suppresses the development of a trait controlled by gene B. Determine the probability of the birth of a colored chicken from crossing chickens with the AABb and aaBb genotype.
Solution:
A - a gene that determines the formation of color;
a - a gene that does not determine the formation of color;
B - a gene that suppresses the formation of color;
b - a gene that does not affect the formation of color.
aaBB, aaBb, aabb - white color (no allele A in the genotype),
AAbb, Aabb - colored plumage (the A allele is present in the genotype and the B allele is absent),
AABB, AABb, AaBB, AaBb - white color (in the genotype there is an allele B, which suppresses the manifestation of the allele A).
The presence of dominant alleles of gene A and gene I in the genotype of one of the parents gives them a white plumage color, the presence of two recessive alleles a gives the other parent also a white plumage color. When crossing chickens with the AABb and aaBb genotypes, it is possible to obtain chickens with colored plumage in the offspring, since individuals form gametes of two types, when merged, a zygote with both dominant genes A and B can be formed.
Crossing scheme:
Thus, with this crossing, the probability of obtaining white chickens in the offspring is 75% (genotypes: AaBB, AaBb and AaBb), and colored - 25% (Aabb genotype).
Answer:
The probability of the birth of a painted chicken (Aabb) is 25%.
Task 3
When crossing pure lines of brown and white dogs, all offspring had a white color. Among the offspring of the resulting hybrids were 118 white, 32 black, 10 brown dogs. Define inheritance types.
Solution:
A - a gene that determines the formation of a black color;
a - a gene that causes the formation of a brown color;
J is a gene that suppresses color formation;
j - a gene that does not affect the formation of color.
1. The offspring of F 1 is uniform. This indicates that the parents were homozygous and the white color trait is dominant.
2. Hybrids of the first generation F 1 are heterozygous (obtained from parents with different genotypes and have splitting in F 2).
3. There are three classes of phenotypes in the second generation, but segregation differs from segregation in codominance (1:2:1) or complementary inheritance (9:6:1, 9:3:4, 9:7 or 9:3:3 :one).
4. Suppose that the trait is determined by the opposite action of two pairs of genes, and individuals in which both pairs of genes are in a recessive state (aajj) differ in phenotype from individuals in which the action of the gene is not suppressed. The 12:3:1 cleavage in the offspring confirms this assumption.
First cross scheme:
Second cross scheme:
Answer:
Parental genotypes are aajj and AAJJ; F1 offspring are AaJj. Example of dominant epistasis.
Task 4
The coloration of mice is determined by two pairs of non-allelic genes. The dominant gene of one pair determines the gray color, its recessive allele is black. The dominant allele of the other pair contributes to the manifestation of color, its recessive allele suppresses color. When gray mice were crossed with white mice, the offspring were all gray. When crossing F 1 offspring, 58 gray, 19 black and 14 white mice were obtained. Determine the genotypes of parents and offspring, as well as the type of inheritance of traits.
Solution:
A - a gene that determines the formation of a gray color;
a - a gene that determines the formation of a black color;
J is a gene that contributes to the formation of color;
j is a gene that suppresses the formation of color.
1. The offspring of F 1 is uniform. This indicates that the parents were homozygous and the gray trait dominates the black.
2. Hybrids of the first generation F 1 are heterozygous (obtained from parents with different genotypes and have splitting in F 2). A splitting of 9:3:4 (58:19:14), indicates the type of inheritance - single recessive epistasis.
First cross scheme:
Second cross scheme:
3. In the F2 offspring, a 9:4:3 splitting is observed, which is characteristic of a single recessive epistasis.
Answer:
The original organisms had the AAJJ and aajj genotypes. Uniform progeny F 1 carried the AaJj genotype; in the F2 progeny, a 12:4:3 splitting was observed, characteristic of a single recessive epistasis.
Task 5
The so-called Bombay phenomenon is that in a family where the father had I (0) blood type, and the mother III (B), a girl was born with I (0) blood type. She married a man with II (A) blood group, they had two girls with IV (AB) group and I (0) group. The appearance of a girl with group IV (AB) from a mother with group I (0) caused bewilderment. Scientists explain this by the action of a rare recessive epistatic gene that suppresses blood types A and B.
a) Determine the genotype of the indicated parents.
b) Determine the probability of having children with group I (0) from a daughter with group IV (AB) from a man with the same genotype.
c) Determine the probable blood types of children from the marriage of a daughter with I (0) blood type, if the man is with IV (AB) group, heterozygous for the epistatic gene.
Solution:
In this case, the blood type will be determined in this way
a) The recessive epistatic gene shows its effect in the homozygous state. Parents are heterozygous for this gene, since they had a daughter with I (0) blood group, in which a girl with IV (AB) blood group was born from a marriage with a man with II (A) group. This means that she is a carrier of the IB gene, which is suppressed in her by the recessive epistatic w gene.
Diagram showing the crossing of parents:
A diagram showing the crossing of a daughter:
Answer:
The genotype of the mother is IBIBWw, the genotype of the father is I0I0Ww, the genotype of the daughter is IBI0ww and her husband is I0I0Ww.
A diagram showing the crossing of a daughter with group IV (AB) and a male with the same genotype:
Answer:
The probability of having children with I (0) gr. is equal to 25%.
Scheme showing the crossing of a daughter with group I (0) and a male with group IV (AB) heterozygous for the epistatic gene:
Answer:
The probability of having children with I (0) gr. equal to 50%, with II (B) gr. - 25% and with II (A) gr. - 25%.
In medicine, four blood groups are described in detail. All of them differ in the location of agglutinins on the surface of erythrocytes. This property is encoded genetically with the help of proteins A, B and H. Bombay syndrome is very rarely recorded in humans. This anomaly is characterized by the presence of the fifth blood group. In patients with the phenomenon, there are no proteins that are determined in the norm. The feature is formed at the stage of intrauterine development, that is, it has a genetic nature. This characteristic of the main fluid of the body is rare and does not exceed one case in ten million.
5 blood type or the history of the Bombay phenomenon
This feature was discovered and described not so long ago, in 1952. The first cases of the absence of antigens A, B and H in humans were registered in India. It is here that the percentage of the population with an anomaly is the highest and is 1 case in 7600. The discovery of Bombay syndrome, that is, a rare blood type, occurred as a result of studying fluid samples using mass spectrometry. Analyzes were made because of the epidemic in the country of such a disease as malaria. The name of the defect was in honor of the Indian city.
Bombay blood theories
Presumably, the anomaly was formed against the background of frequent related marriages. They are common in India due to social customs. Incest not only led to an increase in the prevalence of genetic diseases, but to the emergence of the Bombay syndrome. This feature is currently found in only 0.0001% of the world's population. A rare characteristic of the main fluid in the human body may remain unrecognized due to the imperfection of modern diagnostic methods.
Development mechanism
In total, four blood types are described in detail in medicine. This division is based on the location of agglutinins on the surface of erythrocytes. Outwardly, these characteristics do not appear in any way. However, they need to be known in order to carry out a blood transfusion from one person to another. If the groups do not match, reactions can occur that can lead to the death of the patient.
This phenomenon is completely determined by the chromosome set of parents, that is, it has a hereditary character. The laying occurs at the stage of intrauterine development. For example, if the father has the first blood type, and the mother has the fourth, then the child will have a second or third. This characteristic is due to combinations of antigens A, B and H. Bombay syndrome occurs against the background of recessive epistasis - a non-allelic interaction. This is what causes the absence of blood proteins.
Features of life and problems with paternity
The presence of this anomaly does not affect human health in any way. A child or adult may not be aware of the presence of a unique feature of the body. Difficulties arise only if the patient needs a blood transfusion. Such people are universal donors. This means that their liquid will suit everyone. However, when defining Bombay syndrome, the patient will need the same unique group. Otherwise, the patient will face incompatibility, which will mean a threat to life and health.
Another problem is the confirmation of paternity. The procedure in people with this blood type is difficult. The determination of family ties is based on the detection of relevant proteins that are not detected when the patient has Bombay syndrome. Therefore, in doubtful situations, more difficult genetic tests will be required.
In modern medicine, no pathologies associated with a rare blood group have been described. Perhaps this feature is caused by the low prevalence of Bombay syndrome. It is assumed that many patients with the phenomenon are unaware of its presence. However, a case of revealing a rare hemolytic disease in a newborn baby whose mother had the fifth blood group is described. The diagnosis was confirmed on the basis of the results of the screening of antibodies, the study of lectins and the determination of the location of agglutinins on the surface of the erythrocytes of the mother and child.
Pathology diagnosed in a patient is accompanied by life-threatening processes. These features are associated with the incompatibility of the blood of the parent and fetus. At the same time, two patients suffer from the disease at once. In the described case, the mother's hematocrit was only 11%, which did not allow her to become a donor for the child.
A big problem in such cases is the lack of this rare type of physiological fluid in blood banks. This is primarily due to the low prevalence of Bombay syndrome. The difficulty is also the fact that patients may not be aware of the features. At the same time, according to the available data, many people with the fifth group willingly agree to be donors, since they realize the importance of creating a blood bank. In case of hemolytic disease of the newborn against the background of the diagnosis of Bombay syndrome in the mother, the cases of which are rare, there is also the possibility of conservative treatment without the use of blood transfusion. The effectiveness of such therapy depends on the severity of pathological changes in the body of the mother and child.
The Importance of Unique Blood
The anomaly is considered poorly understood. Therefore, it is too early to talk about the impact of the feature on the health of the planet's population and medicine. It is indisputable that the occurrence of the Bombay syndrome complicates the already difficult procedure of blood transfusion. The presence of a 5th blood group in a person endangers life and health when a transfusion becomes necessary. At the same time, a number of scientists are inclined to believe that such an evolutionary event may have a beneficial effect in the future, since such a structure of the biological fluid is considered perfect in comparison with other common options.
