Chimeras

I have mentioned chimeras before, but here's a little more detailed information.

An ancient coin depicting a chimera

The chimera was a creature from Greek mythology. It was a hybrid creature, consisting of the front of a lion, the back of a goat, and a snake tail. Though female, it had the mane of a male lion. It was also said to breath fire and to be an omen of natural disasters, including volcanoes, as well as shipwrecks and storms.

The modern definition of chimera is also of a combined creature, but of a very different sort. Instead of a combination of different animals, a chimera is basically twins in one body. Twins are conceived, but one dies during development. Instead of the dead twin being lost, the two embryos fuse together, leading to a single embryo with two different sets of genetic material. It is not uncommon for individuals to go their entire lives without being aware of their unique genetics. Many chimeras will have no visible signs of the abnormality. In contrast, however, other chimeras will be visible at birth. Since there are two genotypes involved, it is very possible for a chimera to have two different skin pigments, eye colors, or hair colors present, as seen in the mouse below. If the chimera is produced from opposite-sex twins, it would also be possible for abnormalities to occur in the genitals.

A chimeric mouse with her offspring.

Sources are Greek Gods and MedicineNet. Images are from Wikimedia Commons and are under a creative commons license or are copyright free: one, two