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Deryni Genetics

Started by CapnGramma, April 24, 2023, 03:25:18 PM

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When Katherine Kurtz wrote the original Deryni trillogy she had a general concept of how Deryniness was inherited. This was published in an appendix of the book "High Deryni."

Shortly after that, several characters seemed to break the rules.

I found a way to explain some of those discrepancies.


Originally thought to ride only on the X' chromosome, Deryniness itself is actually a complex set of genetic keys that unlocked various abilities that may be available in some people. Some are dominant traits, others recessive.  A few talents even depend on the presence of a series of genetic keys and traits.  Healing is one such talent and the blocking of powers is a further subset of the healing ability.

There are also two "master" keys.  Each is sex linked.  The X' key is common in almost all deryni and is very easy to detect in even the youngest children.  This key automatically activates itself, unlocking any basic skills present in the child.  The Y' key is more difficult to detect, but potentially much more powerful.  The Y' key not only unlocks the full deryni potential, it also decodes RNA messages and allows the man with these powers immediate access to whatever deryni powers were included in the "unlocking" ritual. Since the genes that turn an X into an X' and the Y into a Y' chromosome are only keys, it is possible to have that gene and pass it on to a child even though the parent has no discernable deryni powers.

It is also possible to have deryni powers without one of these "master" keys.  A person can be born with enough specific keys to specific areas to unlock a few specific talents.  Truth reading requires only a few of these specific keys and does not require all be present to unlock parts of the talent.  Healing requires several keys and if even one is missing, the talent will be blocked. 

There are several talents that are unlocked only by their specific keys.  The primary healing function is only one of these.  Each of the four domains, healing, defense, communication, and death have their own keys, and all these keys must be activated.  This activation can take the form of a ritual, but more often responds to a situational trigger.  While a few functions associated with each of these areas could possibly be available to many deryni, the full potential will be available only to those few deryni who possess all the keys and all the traits for the series.

As an analogy, consider a set of post office boxes. The letter carrier has a key, X' or Y', that unlocks the whole front of the set, allowing access to anything available within those boxes. If all the boxes are empty, having the key doesn't mean anything. If most of the boxes have usable contents, the person will be able to access them. However, if a particular trait doesn't exist the person will not be able to develop the ability associated with that talent. This explains why Thorne Hagan is unable to completely master the water spell. It also explains how the "human" Maryse and Deryni Duncan were able to have an X' deryni son. It's likely she was an X' Deryni but didn't have many talents – she had the key, but not the contents. Or, she may have had some skills, but no way to recognize them as more than Borderer Second Sight, and certainly no training.

To expand the analogy, consider the possibility that one or more of the boxes hold containers that require an additional key to access their contents. This would prevent deryni with the X' or Y' key from using the trait it contains. Thus, only deryni with the additional keys for the various healing talents can learn to heal.

Additionally, just as each box in the set of post office boxes has its own key, many traits have individual keys. A person lucky enough to have the correct series of keys and traits can develop the abilities associated with them. This explains the development of "rogue" talent like Warin and Derry.  It also accounts for the "second sight" in the border folk. 

During the post-interregnum persecutions, many deryni denied their abilities, and blended into the general population. The blocking talent that some healers were able to perform made it possible to hide even from the testing methods designed to detect deryni. The blocked deryni, and their descendants, interbred with the non-deryni through the next 200 years. This meant that, by King Kelson's time, many people had some deryni blood.


I like this as a good analogy for the variation in Deryni abilities for different characters. I strongly believe there are several genes (post-office box's) that allow for many different skill levels within the Deryni population and there is one gene/key that lets you get into those different box if they have stuff in them.  And I like also your explanation of second sight and Warren de Grey, that under certain combinations that One gene/key is not always necessary.

I read the X and Y article many times. and I know that KK has since changed her mind on that idea as her story grew. She said she found it too limiting. In our modern age of technology, so much more has been discovered about genetics, which had only been guessed at in the 1970-80's. The easiest thing to say is that the sex-linked genetics theory was the "Medieval" way of looking at the problem and the modern view has taught us there is so much more to it than just one Gene and the X chromosome.

I do like your idea that Maryse could have been a carrier of the X Deryni gene because of the 200 years of diverse inheritance. So that is a good explanation. but I really would like to think that the Haldane gene affects more than just the males. For the sake of all the Haldane queens who will inherit the throne in the future, I hope that gene is not discovered on just the Y gene.
May your horses have wings and fly!


I do remember the article as an appendix to one of the original novels. I liked the idea of a genetic basis for Deryni abilities, and I did wonder whether KK was going to expand on it or follow a more supernatural explanation.


KK's officially abandoned the X-linked, Y-linked idea, but I still like playing with it.

My newest theory is that the Y' can happen in women, but it has to be carried on both chromosomes in the pair.