This article is from the WSSF 2015 AFRMA Rat & Mouse Tales news-magazine.

Mosaic is from 1 egg that has different cell make-up from a spontaneous mutation or error in the cell during embryo development.

Chimera is the fusion of 2 eggs with different cell lines (e.g. Seal Point with Blue Point so parts are brown and parts are blue). They can also be when an animal contains cells from another animal. A Chimera is from the Greek mythology where one animal was comprised of 3 different animals. You can see examples of cat chimeras on the page Tortie Tomcats: Chimeras (down towards the bottom of the page is a photo of a Ragdoll that has the legs on one side of his body blue and the other side of his body are seal).

You can also check out these pages:

• Genetic Mosaics
• Scientists merge mammalian cells from two species, creating chimera

Some sources/people use the terms interchangeably but they are two different things.

See also the AFRMA Tidbit Chimera Mouse.