Genetic memory is a rare trait in which information is carried through generations by DNA. This ability has been observed primarily in Mystical Creatures and has been seen in both Dragons and Unicorns.
Dragon Genetic Memory
According to legend, each dragon carries "the secrets of the multi-verse" coded into his being. In practice, this translates to a encyclopedic knowledge of the physical sciences. Math, chemistry, physics, how the multi-verse functions; all is coded within their DNA. During Antiquity and particularly Classic Antiquity, dragons used this knowledge to educate humans, informing the technological advancement achieved by the Eladamri. With the Fall of Roads and the rise of fallen dragons, the dragon population, as a whole, gradually lost the use of their genetic memory. It is believed the techniques for accessing it had to be passed verbally from one generation to the next, and that during the Mage Wars this failed to happen on many occasions.
Unicorn Genetic Memory
By sharp contrast, each unicorn is born with the complete experiential memories of every unicorn to come before it, up to and including its own birth. While the dragon memory is coded in DNA, the unicorn memory employs a completely magical system. It has not been studied and is very poorly understood.