Chimera:In medical terms, a chimera refers to an individual made up of two different genetic cell types. The concept of human chimeras emerged with blood typing, revealing that some individuals possess more than one blood type. Most cases turned out to be "blood chimeras," typically non-identical twins who shared a blood supply in utero. In situations where the individuals were not twins, it is believed that they acquired blood cells from an embryo that did not survive early in gestation. Twin embryos frequently share a placental blood supply, enabling blood stem cells to transfer from one twin and integrate into the other. Approximately 8% of non-identical twin pairs are considered chimeras.A larger number of people are classified as microchimeras, harboring small quantities of foreign blood cells that might have crossed from the mother via the placenta or remained from a vanished twin. The practice of in vitro fertilization (IVF) is also increasing the prevalence of human chimeras. To enhance success rates, multiple embryos are often implanted in the uterus, resulting in a higher incidence of twin pregnancies among women who undergo IVF. Consequently, more twins lead to more chimeras.In Greek mythology, the Chimera was a formidable creature that breathed fire and had the head of a lion, the body of a goat, and the tail of a serpent. The hero Bellerophon, often depicted riding Pegasus, the winged horse, ultimately defeated the Chimera.
