Normally, a female egg cell (oocyte) and a male egg cell
(sperm) must combine in order for pregnancy to occur. In the event that two egg
cells merge with two sperm cells, twin pregnancy occurs. In the very rare case
of chimerism, 2 fertilized eggs consisting of the combination of two eggs and
two sperms then combine to form a single fetus. The fetus, that is, the baby
that was born later, is actually like a single creature consisting of the
genetic structure and tissues of the two siblings. This creature, which occurs
with the subject of chimerism, is called "chimeric" or "chimeric
human". It is an event that can rarely be seen not only in humans, but
also in other living things. The event is sometimes called tetragametic chimerism.
Because it is a creature that is formed by the merger of 4 cells, 2 egg cells
and 2 sperm cells.
The combination of two fertilized eggs occurs at the
blastomer stage or at the gastrula stage.
Another
type of event that causes confusion due to chimerism is when the baby is
investigated whether it belongs to the mother or not.: (Chimerism test)
When the chimeric person reaches adult age and becomes
pregnant, the baby to be born will not normally be chimeric and will have a
genetic structure that is formed by the combination of the cell from the
mother's ovary and the sperm from the father. There are 2 different genetic
structures in the mother's body in different tissues, but the baby has taken
only one of them. In a genetic study to be done if the baby belongs to the mother,
the genetic material taken from the mother may be different with the baby.
Another tissue sample taken from the mother may be the same as the baby. There
have been criminal problems experienced in this way.
There will be no problem in a motherhood examination between
the chimeric man and his mother. Whichever tissue it is taken, the sample will
be compatible with the mother.
Chimera in
mythology:
The name chimerism comes from the chimera in mythology. In
mythology, Kimera is a creature whose body is a mixture of three different
animals (lion, goat, snake).
Microchimerism
Microchimerism is the presence of a small number of cells in
one living creature in another. Cells that will form two separate creatures,
such as in chimerism, do not merge and form a single creature. Pregnancy is the
most frequently observed microchimerism (Mc). The best example explaining
microchimerism is that some cells belonging to the baby pass to the mother
during pregnancy and remain in some tissues of the mother. On the contrary, the
mother's cells can pass to the baby during pregnancy and remain in the baby's
body for years after birth. This cell transition between mother and baby is
called fetomaternal microchimerism. In a study, it was found that there are
cells belonging to the baby born 27 years ago in the mother's blood.
Microchimerism is thought to be related to various diseases,
especially autoimmune diseases in women, and there is extensive research in
this direction.
Apart from pregnancy, applications such as blood transfusion
and organ transplantation can also cause microchimerism.
-WHAT SHOULD BE DONE TO HAVE TWIN PREGNANCY?
-IDENTICAL TWINS
-FRATERNAL TWINS
-TRIPLET PREGNANCY
-NORMAL BIRTH OR CESAREAN IN TWIN PREGNANCIES?
-TWIN TO TWIN TRANSFUSION SYNDROME
-CAN THERE BE TWIN BABIES FROM DIFFERENT FATHERS?
-CAN ANOTHER PREGNANCY OCCUR DURING PREGNANCY?
-VANISHING TWIN SYNDROME
-FETUS IN FETU (FIF)
-CHIMERISM
