Why do parents and children have different Rh factors: what if the father and mother are positive, and the offspring are negative? How is the Rh factor inherited in humans?

My wife and I have positive Rh blood factors, and our son is negative. Can this really happen? Nikolay N., Grodno region.

Viktor Andreev, professor of the Department of Medical Biology and General Genetics, GrSMU:

For a long time, people have noted that a child is not an exact copy of its parents. It happens that children have traits that are not characteristic of either the mother or the father.
Many hypotheses have been put forward to explain such observations. The most widely accepted concept is fused heredity. According to it, the totality of all the characteristics of each parent is transmitted as a whole to the descendant, in whom they are mixed and lose their individuality.

Proponents of this opinion consider the hereditary substance to be a fused and precisely divided material. Its symbol is blood. Echoes of such an idea are the expressions “purebred”, “half-breed” (in relation to animals), “consanguinity”, “blue blood”, preserved from the beginning of the 18th century. The difference between the descendant and the father and mother was explained by mixing, and between sisters and brothers - by the variability of the “blood strength” of the parents. The argument in favor of fused heredity is that some characteristics of the descendants are a cross between the characteristics of the parents. Such a speculative interpretation raises many questions for the spouses to each other.

The founder of the experimentally proven scientific theory of discrete (separate) heredity was Gregor Johann Mendel (1822–1884). The scientist discovered the fundamental laws of inheritance and showed that the descendant receives factors, which today are called genes, from each of the parents.
A gene determines the formation of one elementary trait, while the latter can have several specific manifestations (in genetics - phenes).

For example, the color of the iris is brown or blue; eyelashes - long, short or medium; lips - thin, full or medium full; hair is straight or curly. These varieties (versions, states) are called alleles. Of the alleles of a gene, only 2 can be in a person’s genotype - from the mother and from the father. Genes do not merge, but during the formation of germ cells they diverge independently of each other. One gamete (sperm or egg) gets one allele, and the other gets another.

Alleles can be dominant and recessive (from the Latin recessus - retreat); the latter are not phenotypically manifested in the presence of the dominant allele.
The dominant allele that determines the Rh-positive blood group is Rh; recessive, or hidden, - rh. Allelic pairs of genes are made up during fertilization - the egg will have one of the possible combinations: RhRh, Rhrh or rhrh.

If both parents have Rh-negative blood (their genotypes are rhrh and rhrh), then a child cannot be born who is Rh-positive.

In the case where the mother and father are Rh positive and their genotypes are homozygous for the dominant allele (RhRh and RhRh), all children will have Rh positive blood (RhRh genotype).

Since the author of the letter and his wife have a child with Rh-negative blood, then, according to the discrete theory of heredity, the parents are heterozygous by genotype, i.e., each genotype has both dominant and recessive alleles (the genotype of the father is Rhrh; the genotype of the mother is Rhrh). In such a family, a son or daughter can have both Rh-positive and Rh-negative blood.

What blood type will the future baby inherit? - this question worries many couples who are “waiting for a miracle.” To find out, we will tell you what blood type and Rh factor are, and whether it is possible to predict in advance what they will be like in a child.

What is blood?

Blood is nothing more than a liquid tissue that circulates inside the human body and maintains proper metabolism.

It consists of:

liquid part, that is, plasma and cellular elements;
erythrocytes and leukocytes;
platelets;
gas (nitrogen, oxygen and carbon dioxide);
from organic substances, which include proteins, carbohydrates, fats and nitrogenous compounds.

What are the different blood types?

Blood type is nothing more than a difference in the structure of proteins. As an indicator, it cannot change under any circumstances. Therefore, blood group can be considered a constant value.

It was discovered by the scientist Karl Landsteiner at the dawn of the 19th century, who stood at the origins of the definition of the AVO system.

According to this system, blood is divided into 4 known groups:

I (0) - group in which antigens A and B are absent (molecules involved in the formation of immunological memory);
II (A) - blood with antigen A in its composition;
III (B) - blood with antigen B;
IV (AB) - this group contains two antigens, A and B.

The unique ABO (blood group) system changed scientists' understanding of the composition and nature of blood and, most importantly, helped to avoid errors during transfusion that occurred as a result of incompatibility of the patient's blood with the donor's.

Rh factor - what is it?

The Rh factor is a protein antigen found on the surface of red blood cells. Scientists first discovered it back in 1919 in monkeys and a little later confirmed the existence of the Rh factor in humans.

The Rh factor includes more than 40 antigens, which are designated using numbers and letters. The most common Rh antigens found in nature are D (85%), C (70%), E (30%) and E (80%).

According to statistics, 85% of Europeans become carriers of a positive Rh factor, and the remaining 15% - negative.

Rh factor mixing

Surely you have heard that when mixing the blood of parents with different Rh factors, a conflict often occurs. This happens if the mother is Rh negative and the father is Rh positive. In this case, the child’s health depends primarily on whose rhesus is “stronger.”

If the future baby decides to inherit the father’s blood, then the mother’s blood will “increase” the content of Rh antibodies every day. The problem is that, penetrating inside the fetus, they will destroy red blood cells, then the body itself, which ultimately can lead to hemolytic disease of the baby.

What are Mendel's laws?

The laws of Gregor Mendel, an Austrian biologist, which geneticists and doctors rely on, are nothing more than a clear description of the principles of inheritance of certain characteristics.

They served as a strong basis for the subsequent emergence of the science of genetics, and it is on them that one should rely when predicting the blood type of a child.

Principles of inheritance of blood groups according to Mendel

According to the laws of Gregor Mendel, if parents have blood type 1, they will have children without antigens A and B.
If the parents of the unborn baby have blood groups 1 and 2, then the children will inherit them. The same applies to groups 1 and 3.
Blood group 4 is a chance to conceive children with group 2, 3 or 4, excluding the first.
The child’s blood type is not predicted in advance if his parents are carriers of groups 2 and 3.

The “Bombay phenomenon” became an exception to these rules that have not changed over the years. It's about about people whose phenotype contains A and B antigens, but for some reason they do not manifest themselves in any way. This situation occurs very rarely and most often among Indians.

How is the Rh factor inherited?

The Rh factor is designated by the letters Rh. Being positive, it carries the prefix “plus”, and negative – the sign “minus”.

It is possible to guess its type with 100% accuracy only in the case when both parents are Rh negative; in all other cases, Rh will be different.

Inheritance system

The positive Rh factor, which is determined by the D gene, has different alleles in its structure: dominant (D) and recessive (d). In other words, a person with the Rh(+) type can carry both the DD and Dd genotypes. A person with Rh(-) Rhesus is a carrier of type dd.

Knowing this pattern of inheritance, it is quite possible to predict the future Rh factor in a child who has not yet been born. If the mother is negative with the dd genotype, and the father is positive (DD or Dd), then the baby can inherit any of the possible variants. This is clearly demonstrated by the following table:

Thus, if the father carries the DD type, the offspring of the couple will receive Rh-positive Rhesus, and if he has the Dd type, then this probability is reduced to 50%.

What else can a baby inherit?

Of course, parents are concerned not only with what blood type their child will have. They are also wildly curious whether the baby will inherit, for example, their eye or hair color.

Dominants and recessives

Such intriguing questions are answered by genetics, and this is done through its knowledge of two types of genes: dominant and recessive. The former always precede the latter and suppress them.

Overwhelming, dominant signs include such appearance features as blood type, freckles or dark skin, dimples, fluffy eyelashes, a hump on the nose, myopia or early graying.

So, for example, if the father has brown eyes and the mother has blue eyes, the toddler will have dark eyes.

Traits that are inherited

The following can be inherited:

blood type and Rh factor (as we found out earlier);
color of the skin;
vision features (myopia or strabismus and other defects);
height (short or tall);
individual structural features of the arms and legs;
hearing characteristics (musical hearing, normal or deafness);
facial features (including freckles and dimples);
shape of the mouth, nose and ears;
hair color;
diseases (for example, diabetes and hemophilia).

But it is quite difficult to predict the baby’s character based on these signs. If only you try to determine the psychotype of personality to which the child will belong.

What about IQ?

Of course, a child can take not only the blood type and external signs from his parents. However, the IQ value, which expectant mothers and fathers are also often worried about, does not greatly depend on heredity.

Oddly enough, for the development of a child’s intelligence and brain, a favorable family environment and early communication bring much greater benefit than heredity.

At the same time, according to experts, women who constantly exercise during pregnancy can give birth to a gifted child. It also stimulates the child's mental activity and breast-feeding(increases IQ by 6 units).

Health issue

As for diseases, everything has been known for a long time that, unfortunately, along with eye and hair color, a bunch of various diseases can be transmitted to us from our parents, including allergies, schizophrenia and even mental retardation.

But there is good news: today a person can receive his own individual genetic passport in order to find out about the dangers that threaten him. You can get it by contacting a medical laboratory that deals with DNA tests and genetic studies (and not just standard tests such as blood type and Rh factor).

Having done such an analysis, you will receive a personal “decoding” of the body’s characteristics, which will indicate a tendency to certain diseases, an attitude towards sports, a list of foods undesirable for consumption, and even a list of climatic conditions unfavorable for living.

AnnaMalia

06.08.2009, 18:27

Mom and Kiklan

06.08.2009, 18:35

From what I read, I realized that the negative ones have only negative ones.

06.08.2009, 19:18

No.
positive ones can have a negative child, but negative ones cannot have a positive child

06.08.2009, 20:28

The child's Rh may be incorrectly determined, and so can the parents.

06.08.2009, 21:55

If Rhesus has the same mechanism as the group, then it can. you need to ask the geneticists

Mom and Kiklan

06.08.2009, 22:17

maybe, why not? why only in one direction, please explain, or provide a link. Let’s say the parents are Rh+ Rh+, and the child is Rh- this same Rh that got lost along the way?

Try using a search engine, I just looked at the Rhesus inheritance table, there, negative people are inherited 100%.

06.08.2009, 22:30

found it.
Patterns of inheritance of blood group and Rh factor.

Inheritance of blood type is controlled by an autosomal gene. The locus of this gene is designated by the letter I, and its three alleles by the letters A, B and 0. Alleles A and B are equally dominant, and allele 0 is recessive to both of them. There are four blood types. The following genotypes correspond to them:

First (I) 00

Second (II) AA; A0

Third (III) BB; B0

Fourth (IV) AB

Example 1:

The husband has a second blood group and is homozygous (AA)

Wife 00 + husband AA

Gametes: 0 0 A A

Child: A0 A0 A0 A0

All children have a second blood group and are heterozygotes for this trait.

Example 2:
wife has blood type O (00)

The husband has a second blood group and is heterozygous (A0)

Wife 00 + husband A0

Gametes: 0 0 A 0

Child: A0 A0 00 00

In a given family, in 50% of cases it is possible to have a child with the second blood group, and in 50% of cases the birth of a child with the first blood group.

Rh factor inheritance
encoded by three pairs of genes and occurs regardless of blood type inheritance. The most significant gene is designated by the Latin letter D. It can be dominant - D, or recessive - d. The genotype of a Rh-positive person can be homozygous - DD, or heterozygous - Dd. The genotype of a Rh negative person may be dd.

Example 1:

The husband has a positive Rh factor and is heterozygous (Dd)

Wife dd + husband Dd

Gametes: d d D d

Child: Dd Dd dd dd

In a given family, the probability of having a Rh-positive child is 50% and the probability of having a Rh-negative child is also 50%.

Example 2:
wife has a negative Rh factor (dd)

The husband has a positive Rh factor and is homozygous for this trait (DD)

Wife dd + husband DD

Gametes: d d D D

Child: Dd Dd Dd Dd

In this family, the probability of having a Rh-positive child is 100%.

I continue the topic.

gametes D d D d
children DD+, Dd+, Dd+ and dd -

I don't pretend to be true.

06.08.2009, 22:54

06.08.2009, 23:00

Maybe. I have IV-, my husband has I-.
I thought that children could only be in denial. She gave birth to her second child in the 1st birth period (Rhesus-conflict) and there all children have their blood type determined at birth. Imagine my surprise when it turned out that the child had II+. (I am sure of my husband’s paternity:)))
I asked the doctor why the group turned out like this, maybe the analysis was mixed up?
I was told that this could happen.
Now I want to find out the blood type of my eldest son. Maybe not like my mother or my father either :)
If your child was Rh-conflicted, then he was positive. This was confirmed. This means that my husband’s Rh is incorrectly determined.
Only “negative” women have “conflict” children.
Well, you know better about paternity. ;):) Most likely, my husband’s Rh was incorrectly determined. May bi cross reaction...
Well, we solved all the problems a page earlier.

AnnaMalia

06.08.2009, 23:16

She calmed the parents down and sent everyone to re-donate blood.

Kirillova-mother

07.08.2009, 14:43

found it.
[
I continue the topic.
examples not previously considered.
3. wife with positive Rh heterozygote Dd and husband with positive heterozygote Dd
gametes D d D d
children DD+, Dd+, Dd+ and dd -

4. well, dd and dd (both negative parent) cannot have either heterozygous Dd or homozygous DD positive children, only dd-, dd-, dd-, dd-.:(
because here there are only zygotes d d d d

5. Dd is positive. one parent + DD pos. other = all positive homo DD DD and hetero Dd Dd children

6. DD+ and DD+ - positive parents = only homozygous positive DD DD DD DD children.

Maybe there are pitfalls?
I don't pretend to be true.

When I was pregnant, my husband and I also read something like this. My daughter was born - there’s no way there’s a group like hers! (According to the table:).) The husband came to the doctors, stamped his feet - “you defined it incorrectly, redefine it immediately!” They drove him away with the words “go, young man, everything is correct, and this also happens.”
Pys. This is OUR daughter. No options.

07.08.2009, 17:13

07.08.2009, 18:15

I'll tell you too. Having become pregnant, I went for a test to determine the gr. blood. I always knew that I had 1-, and that’s what it says on the certificate from the maternity hospital (when I was born). According to the results of the residential complex: 1+. I had to retake it again in another place - the same thing. I called my mom: she did too, to which my mom shouted down the phone: just don’t tell dad (there was no reason, but he’s very suspicious - “first he hits, then he sorts it out” :)). My mother donated blood again, she also became a +, then my dad was prepared and his blood was donated - he also turned out to be a +. So for 25 years my family was all “-”, and during my pregnancy everyone became “+”. Let me note that my dad donated blood several times when he was young, and was always “-”, just like my mother’s. Same. No one received transfusions.

07.08.2009, 19:32

Well, it's simple!
Rh negative parents can only have Rh negative rhe.
About 80% of the human population has the Rh antigen (conventionally called Rh-positive). But others do not (Rh-negative). If neither mom nor dad has this antigen, where does it come from? All the stories when Rh-negative parents give birth to Rh-positive children are most likely an error in determining the parents' Rh or Rh.

07.08.2009, 22:32

About homo and heterozygotes, I think I know more than you.

:009:

Genetics is a science. This is not fortune telling on coffee grounds!

07.08.2009, 22:41

Well, what I know, only I know;)
and in categorical things it is not permissible to write IMHO, IMHO... You write bookish truths.
Okay, I'm gone:020:

Dasha-Petya

07.08.2009, 23:07

Still, I’ll correct myself... I wrote some nonsense at first.
There is a variant of a “weak” Rh factor, when laboratory errors are very likely. They can determine “-” rhesus, when in fact it is “weak”, but “+”. Then there is a possibility of having a child with “+”.

07.08.2009, 23:31

09.08.2009, 18:51

About homo and heterozygotes, I think I know more than you.
Rhesus antigen is dominant. That is. if it is, in any case the Rh will be positive.
RhRh-homozygous. Rh-positive
Rhrh-heterozygote.Rh-positive.
rhrh- and only in this case is Rh negative.
:009:
IMHO about eyes and skin color: characteristics such as hair, skin and eye color are encoded NOT BY ONE GEN, but by a combination of several at once.
Genetics is a science. This is not fortune telling on coffee grounds.!}