Two-faced And Chimera Cats – What Causes This Striking Phenomenon?

Two-faced and chimera cats may look photoshopped, but they’re real! Find out what causes this rare phenomenon, from chimerism to genetic variations.

Social media is full of cat videos and photos. These famous felines often have distinctive physical appearances (think Lil Bub) or humorous facial expressions (like Grumpy Cat). “Two-faced” cats such as Venus, Quimera, Narnia and Queen Domiino are particularly eye-catching. These striking felines have sharply delineated and symmetrical facial markings that make them look like two cats spliced together. How does this phenomenon occur?

Many two-faced cats are chimeras

Chimerism happens when cells from two different embryos fuse together in the early stages of pregnancy. This results in a cat becoming one with its non-identical twin. 

Embryo fusion can result in an XY/XY genotype if two male embryos fuse. It can result in XX/XX if two female embryos fuse, or XY/XX if a male and female embryo fuse. Contrary to popular belief, many chimera cats are fertile.

Fun fact: The word “chimera” is rooted in Greek mythology and describes a fire-breathing female monster resembling a lion in the front, a goat in the middle and a dragon at the rear.

In well-known cases of chimerism, cats have different colored eyes (heterochromia) and/or a “split” face of two distinct colors. For example, one side of the face might be black, and the other side orange, while one eye might be blue and the other green. 

When “two” faces aren’t chimerism 

Not all cats with two faces are actual chimeras. For example, calico and tortoiseshell cats are not the same as chimeras, even if they have similar markings. Cat geneticist Leslie Lyons explains that some tortoiseshell cats are mosaics. This means a single fertilized egg resulted in a variety of genetic lines. 

Calicos and tortoiseshells display a wide variety of coat patterns and colors. These may include different colored eyes and “split” faces, but that doesn’t mean they are true chimeras.

Fun fact: People can also be chimeras. Only about 100 cases of human chimeras have been recorded, likely because they display only minor traits, such as minimal skin discoloration. In other words, you might be a chimera and not necessarily know it!

 

Chromosomal condition mimics chimerism  

XXY syndrome, also known as Klinefelter syndrome, is a condition characterized by an additional chromosome. It occurs in male cats and can cause chimera-like markings and sterility. Other health problems, such as developmental issues and a shorter lifespan, may also occur. 

Genetic testing is the only way to determine for certain if a cat is a true chimera.

“We can do a DNA fingerprint — just like on CSI. The DNA from one side of the body should be different than the other,” Leslie says.

Fun fact: Heterochromia doesn’t affect eyesight. Hereditary deafness can occur in white cats, especially if one or both irises are blue.

 

Whether the two-faced cats you see on social media are true chimeras or simply have luck-of-the-draw colorings and markings, you can’t deny their charm!

The post Two-faced and chimera cats – what causes this striking phenomenon? appeared first on Animal Wellness Magazine.