Chimerism DNA Test

The symptoms of chimerism are often discrete and can vary greatly from one person to another. When they exist, physical signs are generally the most visible.

They may include, for example, a difference in eye color (heterochromia), where each eye has a distinct color, or even color variations within the same eye. Some people also have lighter or darker birthmarks or skin patches, as well as differences in hair color or texture depending on body parts.

However, chimerism can also be totally invisible. In some cases, genetic differences only manifest when no apparent symptom, particularly when chimeric cells are located in non-visible areas, such as internal organs.

👉 These genetic differences can only be detected by a specific DNA test, capable of revealing the presence of two distinct genetic heritages in the same person.

It is important to emphasize that the presence of these signs does not automatically mean that you are a carrier of chimerism. Other genetic or medical conditions can cause similar manifestations.

The results of a DNA chimerism test are presented in the form of a table of numbers, called a genetic profile. Each number corresponds to the size of a DNA fragment analyzed at a specific location.

These locations are called loci. These are genetic markers used to analyze different specific areas of your DNA.

👉 Each locus is represented by a pair of numbers, called alleles.

You always inherit two alleles for each locus:

• one from your mother's chromosome,

• one from your father's chromosome.

The set of loci and their alleles constitutes your genetic profile, which is unique to each individual (except for true twins).

When comparing several samples (saliva, hair, nails, etc.), the same loci should normally show the same pairs of numbers.

• If the alleles are identical from one sample to another, the profiles match.

• If several loci show differences, this may indicate the presence of genetic chimerism.

Example:

If a locus displays the numbers 8 and 9 on one sample, these same numbers should appear at the same locus on the other sample.

If another sample displays 8 and 10 at the same locus, this may suggest the presence of a second genetic heritage.

⚠️ Important:

A chimerism can only be confirmed if several loci are different. An isolated difference on a single locus may be due to a natural genetic mutation and is not sufficient to conclude.

A chimeric person, that is to say possessing two distinct genetic heritages, can present very variable effects on their health. These effects can range from a total absence of symptoms to more significant health problems.

In some cases, chimeric cells can interfere with the normal functioning of the organism. This can notably promote the development of autoimmune diseases, when the immune system recognizes certain cells as foreign and attacks them. These reactions can cause inflammation, pain and dysfunction of certain organs, depending on the pathology concerned.

Chimerism can also have an impact on reproductive health. When chimeric cells are present in the reproductive organs, this can cause fertility problems, making conception more difficult, or even impossible. In rarer situations, there may be genetic sex differences, when a person has both genetically male and female cells, which can lead to sexual anomalies or questions related to gender identity.

However, it is important to emphasize that chimerism does not systematically lead to health problems. In many cases, chimeric cells coexist without difficulty with the other cells of the body. The individual may then present no symptoms and be totally unaware of their condition. This situation illustrates the remarkable adaptive capacity of the human body in the face of complex genetic configurations.

In genetics, a chimera refers to a person who has two distinct DNA lineages within their body. Unlike the mythological chimera from ancient Greece, this is a real and scientifically explainable biological phenomenon.

Chimerism can occur in different situations, particularly when:

• an individual absorbs their twin during pregnancy,

• a person receives a blood transfusion,

• an organ transplant has been performed,

• or more generally when a foreign genetic material is introduced into the body.

This is referred to as a genetic mix between two individuals, coexisting in the same organism.

In genetics, the term "ghost twins" designates a phenomenon linked to chimerism, when a twin is absorbed in utero by their brother or sister at the beginning of pregnancy. Although this twin does not develop, their DNA can persist in the carrier individual.

In some cases, the presence of this DNA can have variable effects, touching different aspects of life:

• certain biological predispositions,

• physical or behavioral characteristics,

• or more rarely repercussions on health or psychological well-being.

👉 Only a chimerism DNA test allows identifying the possible presence of a ghost twin, by revealing the coexistence of several genetic profiles in the same person.

This phenomenon, although rare, is scientifically documented and is not specific to humans: it has also been observed in other animal species. It illustrates the complexity of genetic identity and the way invisible influences can shape an individual.