The problem with this 'metaphysical inheritance' is that we as normal people cannot model it since there is no real-world data to support it. As such, that is not scientific!

All val have a mini Valinor in their head. When the Val mate the mini-brain-valinor get to do so psionically as well and their progeny gets into the new baby. Occasionally the pregnancies don't align properly and you get a regular human being born.

The act of mating somehow stimulates the vals psionically active parts which trigger a change in the appropriate cells?

In my continuing thought experiments on the subject, trying to reconcile the text with what has to be the intent (Dominant instead of Recessive), I came across an interesting idea:

We know that the vassal families (Balin, Gracchi, etc) tend to be the repository of any human born of two Vals, and that the Vals (when they can't mate with other Vals) tend to breed with their chosen vassel family/families in order to increase the likelihood of producing a Val.

Do the Vals pass on their physical traits to the Vassals?

For example: Two val'Tensens have a human child, who is then 'given over' to the Balin's. Does this resulting human typically share all the normal val'Tensen traits (silver or blond hair, hawkish nose, overbearing sense of self righteousness) or is it common that they have a different look?

I ask this because--assuming my Dominant theory is correct for the genetics of the Val--it could still rationalize why the Vals tend to interbreed with their Vassals. If the Vassal family carries the PHYSICAL traits of the Val family in question, this could be related to the ability to produce a Val even though it is linked to a dominant inheritable trait. I posited before that the "Val Gene" was simply a transcription factor which 'made dominant' various genes in a normal human which would otherwise not be expressed or would be poorly expressed, so if both sides of the family had the val-linked genes, perhaps this would help in the breeding of another val?

This also brings up a logical extension of this: What happens when a Val breeds with a member of a Vassal Family NOT sworn to their Val line? What happens when a val'Tensen makes a baby with--say--a Gracchi? Would it be like any other Val-Human pairing, or would the inclusion of the val'Assante' genes in the Gracchi bring up the possibility of a val'Assante' being born of the pair? If the "Val Gene" is simply a transcription factor which would activate any gene with the proper promotor element for Val-ness, it is conceivably possible that a val'Assante' could be born (assuming the Gracchi's have the same general appearance and genetics as a val'Assante').

That said, this could be. . . gotten around by having different Transcription Factor genes for EACH of the Val families, which would mean that the specific gene combination from a val'Assante' wouldn't work with an inherited Transcription Factor from--say--a val'Dellenov. This would likely yield a Human, though one who could in theory produce a Val child if the right combination is made with another human, or be lethal (let's face it, the Val's don't always get along. . . ). I am coming to like THIS theory because it could also explain some stuff with inter-breeding between Val lines:

Say a val'Abebi has a putrification fetish and decides to get it on with a val'Mordane. We know from canon that when two different Vals have kids (unless one of them is a val'Sungha) there appears to be a 50/50 chance that the Val will be of one line or the other. Perhaps in this situation you have the Val-line based on which TF gets inherited (this could be complicated if both parents are Homozygous Dominant, implying that they have two-copies of their Gene. . .), COMBINED with the presence of the appropriate Val-line genes. As such, it is theoretically possible that the resulting child will have a full set of Abebi AND Mordane genes, but if they inherit ONLY the Abebi TF gene they will only express those genes (and have the skin-tone, build, powers, etc) and the Mordane genes will simply become silenced by lack of the TF.

Another idea is based on the ill-understood science of gene-silencing, where humans can simply shut off specific genes by chemically modifying them so that they cannot (easily) be transcribed. Maybe each "Val Gene" carries a type of Gene-Silencer protein as well which effectively acts as an immune-system to 'reject' the other Val's physical genes? This could also be applied to the complicated issue of Two "Pure" Vals breeding, where the presence of two different (dominant) "Family TF"'s would silence each-other's genes, killing the embryo before it develops, necessitating that only Heterozygous Vals of different families being able to breed with one another.

Okay, brainstorm mostly abated. Thank you for your indulgence. . .

Addendum:

If we go with my present theory (Dominant, family-specific transcription factor with individual family traits regulated by promotors keyed to that transcription factor but otherwise poorly expressed in normal humans), this could also explain (from a genetic basis) the val'Holryns. What if their "family transcription factor" is able to transcribe the "Power Genes" of the different families (if not the physical traits)? This is somewhat harder to rationalize as I believe it has been said that a Holryn (Emman) and a Holryn (Assante') could have a Holryn (Tensen), but it is a possibility.

Yes I would assume there is a tendency for vassal families to take on some of the characteristics of the val families they interbreed with. Along with their own "base" characteristics, and anyone else breeding into the family in consistent numbers.

Marriages between a val family and the vassals of different val family should be rare IMO for cultural reasons. I believe most high level marriages are arraigned to one degree or another. Obviously PCs can claim what they like about their backgrounds. Not really sure what to make of your genetic analysis ... but as a practical matter somewhat of a mute point given that it should be rare. As a theory I find it interesting.

On the last point of "non essential" traits I have always maintained that they blend normally. A val Assante always has grey eyes and blonde hair ... but if a member of the house moved to the Hinterlands and started a family among the Vanomir I believe you'd eventually find blonde haired grey eyed hinterlanders who don't otherwise look all the much like their Coryani cousins. Or maybe the line would die out without lots of infusions from the Coryani stock. I maintain the reason the val families all look the same internally is because of inbreeding and not because some characteristics are so dominant they over ride everything else.

I believe if a val Abebi (very dark skin) and a val Mordane (very pale skin) got together and have a kid then the skin tone of the child would be lighter than his/her val Abebi parent and darker than their val Mordane parent.

My 2 cents

I missed a topic on genetics for a month or so. Oh well, time to add something about genetics.

You have a decent understanding about "dominant" and "recessive" genes, but you are excluding something I best call "dormant" genes. A dormant gene is basically an instruction block that does not function without the proper environment. Without proper conditions, the cells can't produce the proper RNA construction over that area, but it does survive reproduction.

If you have watched "Jurassic Park", all of the lab produced dinosaurs are female when hatched. The story says that in order to get the dinosaur DNA they had to be "complete", they used DNA from a species of frog. Supposedly one of the traits of the frog is that it can change gender if the environment is absent of one. In order for this to occur, the frog's DNA must have instructions for the male reproductive system present in order to construct it. The instructions are present, but they remain dormant until an environmental factor is present.

For the Vals, you can say there are two types of humans. One type of human is generic human, not containing the extra Val chromosome. The other type of human has a Val chromosome present, but the environmental factor needed to operate that chromosome was absent. Without a Val parent, it is impossible for the chromosome to activate, thus remaining dormant. The engine requires a jump start in order to work.

This case opens the possibility that an "extinct" Val family could be genetically backed-up in some human family, presently unused due to lack of the Val "spark" to cause the gene to work. It would require some strange luck in order to return, as long as that lucky human bloodline didn't die out. Val families don't want to willingly take risks for their divine aura to fade out, but there are those black sheep.

this seems to be a decent explanation of what happened with the val'Emman faimly from the 3.5 campaign and their family was locked away in the guise of another one and unlocked by environmental factors

In regards to the ability to change sex, the whole process goes a fair bit beyond "Dormant Genes", which I've mostly covered in the whole concept of Transcription Factors and Promotors (selectively activated genes).

There are two primary methods of sex-determination in animals in the real world: Chromosomal Sex Determination, and Temperature-sensitive Sex Determination (though there are a few that are more complicated). Humans use an XY-sex determination system where XX is female and XY is Male, with abberations of this system leading to many chromosomal disorders (such as Downs Syndrome). There are other variations of this system, such as the ZW-method which tends to work opposite to the XY system (ZZ = Male, ZY = Female); as well as the X0 system where XX is female and X (nothing else) is male. In terms of Temperature Sensitive sex determination--which I believe is seen with Ss'ressen (and maybe ssanu and troglodytes)--where during incubation an enzyme is produced based on the temperature of the environment while the egg is incubating. There are a few other systems that don't quite fit into these categories (such as that found in Clownfish) which are not well known as to the cause, or in the instances of the Platypus which is just BONKERS complicated.

In the case of the frogs which can change their sex, it appears that those species contain a hybrid XY system AND a ZW system, and somehow (not well understood) is able to activate their other set of sex chromosomes to become the opposite sex (or hermaphroditic). While this is a good theory as to how the Val/Human differentiation works, it is generally shown that individual species who do not share the same method of sex-determination CANNOT reproduce, which would suggest that either the Humans in Arcanis are a completely different species to us (using a different system of genetics to us), or that the Vals are merely "Human +" and have additional genes that humans cannot have or cannot express.

It IS possible that it is, as you say, an additional chromosome which causes the Vals. In Humans, I cannot think of a single instance of an extra chromosome giving a POSITIVE benefit (Down's Syndrome, Edward's Syndrome, Warkany Syndrome all cause a variety of physical and mental defects). That said, we do not have any examples of something like the Vals, and it is possible that the Valinor's actually managed to add a whole extra chromosome that (through divine awesomeness) were able to make it in such a way to be genetically stable within a human (and Elroii?. . . and somewhat Ss'ressen). In this case, the chromosome would pass on probably similar to other trisomy disorders (which is to say, not uniformly) and pass all the Val Family's traits with it. The problem is: What happens with two Vals who both pass on this 'extra chromosome'? What if they are from different families? It is the same general discussion as I mentioned in a previous one about possible lethal genotypes.

I'd like to subscribe to this theory, but as far as I'm aware there are NO examples of science ever discovering or adding an extra chromosome beyond a trisomy of an existing chromosome. As such, the results cannot be predicted, and I cannot say it is even possible.