So, while all tert genes are inheritable for the purposes of FR's gameplay, some of them don't really make sense as 'genes'. Here, in my not-at-all-qualified-and-really-just-making-this-up-as-I-go opinion, are which of these contentious genes are genetic and which aren't.
Runes
While pretty, this gene is usually purposely applied through the effects of a spell, and occasionally manifests as a side-effect of a dragon's personal magic reserve. Some propose that genetics might affect how likely you are to spontaneously manifest it, but overall it's not genetic.
Gembond
This is a disease caused by the venom of the onyx cobra. However, it's actually a virus in the venom, and can infect a dragon's offspring. And as viruses altering DNA is one of the ways in which genetics can change, sure, let's call this genetic.
Opal
Some get this confused with gembond, but this one's not a virus, just a mutation that causes scales to fuse together and creates hard patches of skin. Genetic.
Firefly
This is just bug-attracting pheromones. Genetic.
Blossom
This is actually an example of two creatures working in symbiosis. The flowers get to use their roots to draw valuable nutrients from the gaoler's bloodstream, while the gaoler gets to look pretty. The needs of the plants are low enough that the dragon isn't harmed, though having it removed is quite painful. Not genetic.
Braids
This is about as genetic as genetic as your family's ancient braiding technique that's been passed down since time immemorial can be. So, not at all. Not genetic.
Skeletal
This is a weird one. Only the part of the gene attached to the banescale's chest is actually part of the dragon. The rest is just matching bone armour they craft so as to not look silly. Anyways, the chest part is still genetic.
Filigree
This gene is artificially made by carefully pouring hot metal onto the scales and letting it fuse to them and even if you do have scales this still seems like a horrible idea and if you don't why would you even do this!? Not genetic.
Runes
While pretty, this gene is usually purposely applied through the effects of a spell, and occasionally manifests as a side-effect of a dragon's personal magic reserve. Some propose that genetics might affect how likely you are to spontaneously manifest it, but overall it's not genetic.
Gembond
This is a disease caused by the venom of the onyx cobra. However, it's actually a virus in the venom, and can infect a dragon's offspring. And as viruses altering DNA is one of the ways in which genetics can change, sure, let's call this genetic.
Opal
Some get this confused with gembond, but this one's not a virus, just a mutation that causes scales to fuse together and creates hard patches of skin. Genetic.
Firefly
This is just bug-attracting pheromones. Genetic.
Blossom
This is actually an example of two creatures working in symbiosis. The flowers get to use their roots to draw valuable nutrients from the gaoler's bloodstream, while the gaoler gets to look pretty. The needs of the plants are low enough that the dragon isn't harmed, though having it removed is quite painful. Not genetic.
Braids
This is about as genetic as genetic as your family's ancient braiding technique that's been passed down since time immemorial can be. So, not at all. Not genetic.
Skeletal
This is a weird one. Only the part of the gene attached to the banescale's chest is actually part of the dragon. The rest is just matching bone armour they craft so as to not look silly. Anyways, the chest part is still genetic.
Filigree
This gene is artificially made by carefully pouring hot metal onto the scales and letting it fuse to them and even if you do have scales this still seems like a horrible idea and if you don't why would you even do this!? Not genetic.