Blood types: How are they inherited?

How blood types are inherited

The inheritance of blood groups follows a classic Mendelian pattern of genetic inheritance . And, to create a blood type, there are two elements that must be taken into account.

To understand how it works, you have to know the so-called ABO system , created by Karl Landsteiner in 1901, which shows that there are three types of alleles in red blood cells: A, B and O. The A and B alleles are dominant, while the O allele is recessive. On the other hand, in blood, the RH factor It tells us whether or not it includes the D antigen, with the dominant RH+ and the recessive RH-.

That is, with the ABO system and the RH factor, we'll learn about all the existing blood types. Furthermore, this distribution allows us to delineate the inheritance patterns of a blood type. Let's look at some examples:

The inheritance of ABO blood groups

The legacy of the ABO blood groups It is carried out taking into account the allele from each parent. Keep in mind that the A and B alleles are dominant, while the O allele is recessive. Each person has two alleles that they will pass on to their offspring. There are four possible blood types according to the ABO scheme:

• Group A: Group A occurs when the A alleles are combined by each parent or by the combination of the A allele with the O allele.
• Group B: Group B occurs when B alleles or a B allele are combined with the recessive O allele.
• Group AB: Group AB is generated by combining alleles A and B, since both are dominant. The result is a combination of both.
• Group O: This blood type lacks A or B markers in the blood. However, it is the most common in the world.

This factor is crucial when performing transplants or transfusions. Not surprisingly, some blood groups are very rare and must be taken into account. Furthermore, depending on the planet, the proportions of a blood type vary.

The inheritance of the RH factor

The inheritance of the Rh factor is determined by the presence, or absence, of this protein in the blood. Here, the division is much simpler. Let's see:

• RH+ : when this antigen is present in the blood. Most people have this antigen, approximately 80% of the population. Therefore, positive groups are, on average, much more common.
• RH- : if this antigen is not present in the blood. It should be noted that negative groups are generally less common than positive ones.

The combination of the ABO system and the RH factor gives all possible blood types. There are a total of eight possible group combinations, depending on each factor.

Frequently asked questions about blood types and inheritance

The inheritance of blood types has a series of circumstances that must be known to avoid problems. And the predictive genetics can be very helpful in this case. Want to learn more? Keep reading…

What is the most common blood type?

He most common blood type in the world is the O+ An estimated 37.1% of the population has it. However, this distribution varies depending on the region: in the Americas, Oceania, Africa, and parts of Asia, this group is the predominant one, although not in other regions.

Does ethnic origin influence blood inheritance?

Yes , insofar as there are ethnic groups that have a higher prevalence of a certain blood type. This is more evident in endogamous populations or those that have had less migration of people over time.

Do genetic mutations influence the inheritance of blood types?

A genetic mutation can influence in the inheritance of a blood type, although this is not the most common. For this to happen, they must be germline, meaning they must already be present in the eggs or sperm with which the conception will occur. In this case, it is possible that there is a blood type mutation that does not correspond to the genetic inheritance.

However, these are extremely rare situations: a hereditary mutation occurs in only about one in a million cases.

Do blood transfusions have to be from the same blood type?

Yes , precisely so that the blood is compatible and there are no rejection problems that could worsen the situation. Therefore, the first thing that is done, if blood is needed for an operation, is to determine the blood type. Blood tests are usually performed to verify this circumstance and avoid errors that can be fatal.

Is blood type the same throughout life?

It's logical that a person's blood type should remain the same throughout their life. However, today, in cases of bone marrow transplants, somatic genetic mutations (often due to environmental effects) or transplants of other cells may change . In any case, this process should not cause any health problems.

We must also point out that changing groups is the exception, not the rule. In any case, this circumstance will be verified before any surgery or transfusion.

What problems can arise in pregnancy with incompatible RH antigen?

It is perfectly possible that one A mother may be RH+ and her child RH- , which can cause problems during pregnancy, miscarriage, and even serious illness in the mother. This incompatibility is relatively common, so it should be monitored. Fortunately, this can be managed with medication if the condition is known in advance.

What is done, if this happens, is to inject immunoglobulin to avoid problems during pregnancy and after childbirth. Nowadays, if pregnancy is properly monitored, the health outlook is good.

Therefore…

There are various blood types, and heredity is crucial for preventive and health reasons. Genetics, in these cases, is key. At Genotica, you can find a wide range of genetic tests based on your needs. Get to know us . better!