Not everything that is hereditary is a gene, and many genetic characteristics are defined by several genes. As an example, something relatively simple as eye color in humans are defined by 6 gene pairs - that is what generates the variety of eye colors that we know and love - honey, hazelnut, blue, green, brown, black and all the combinations in between.

Something as complex as a werewolf transformation cannot possibly be determined by ONE gene. Even if it was, each gene can be dominant or recessive, so there are 3 possible combinations for each gene, producing at least 3 potential different fenotypes (AA, Aa, aa).

If lycantropism was a gene, there would be potentially 3 different expressions - Werewolf, half-werewolf , not werewolf. The magic folk from Harry Potter seems to follow this rule more closely, as you have magic folk, muggles (non-magic) and squibs (children of magic folk with limited or no magic at all -  but even that is fickle)

But it seems that all descentants of werewolves are potentially werewolves.

Werewolf in TDV universe is a family curse. Somebody and all their descentands were cursed, for some reason I hope we learn someday. Generational curses are mentioned even in the Bible 

God warns that He is “a jealous God, punishing the children for the sin of the fathers to the third and fourth generation of those who hate me.”

It sounds unfair for God to punish children for the sins of their fathers. However, there is more to it than that. The effects of sin are naturally passed down from one generation to the next. 

One is born with their DNA. You inherit one of each DNA pairs from your father and your mother. A copy of them is in every single of your cells - but in each cell only the genes necessary for that cell's form and fuction are active. All the other are dormant.

Although it is theoretically possible to change the DNA somebody was born with, it has not been achieved so far, and poses considerable challenge. 

Scientists are trying to engineer nanobots that act as virus that would deliver the new code to all the cells of a certain organ. That would be useful, for example, to teach pancreas cells in diabetic people to produce insulin - but we are FAR AWAY from these.

I don't believe that either Vampirism or Licantropism in TVD is genetic - even if characters mentioned that it is. I have seen absolutely no evidence of this.

With vampires it's the blood that makes them different, with werewolves what if not genes? Of course they haven't gone into it so it can be anything but I doubt it's the blood because that would be too close to vampires so I'm leaning towards genes until they say anything else on this matter. Case of point:

Katherine mentions in that episode I wrote about earlier that all the Lockwoods all carry the werewolf gene but not all are werewolves because some become dormant or something of the like. We know that George Lockwood was a werewolf so we have to assume either of his parents had the gene but if they werewolves or not we can't say.

You also have to kill someone to trigger it which I think every since the 1900 or so there are far more people with the gene lying dormant, rather than actual werewolves.

In the end though the creators can defend their earlier mistakes with whatever magic ho-ho they can whip up so I doubt any of this necessary.

Well Klaus is geneticly a witch and a werewolf so that means the baby will be part of both species. However Klaus' vampire side could be passed along, and if it is the baby won't be part vampire it will be part dhampir, because vampire means being dead and dhampirs are alive. However Hayley is a member of a subspecies of werewolf (posibly the original pack), so the result of this the baby would be two types of werewolf, part witch and could have a vampiric side. But I think the baby could just be the 2 types werewolf and part witch, but could be turned someday by Klaus.

While his mother was a witch I don't think you can assume Klaus was one before she turned him into a vampire. Not that we have any proof that he wouldn't as the Bennet life for example have passed down linearly, but then there has always been an obvious set up who was going to be a witch (like Grams then Abbie then Bonnie).

Tia Serena@Okay, let me rephrase it. It's a curse that is bound by a gene. You kill the link, you kill the curse.

I just think that the baby will be like every other werewolf, seeing  as it was Klaus's werewolf side that conceived the baby, and Hayley is obviously a werewolf. It will just carry the gene

No, I don't think so. The curse is bound by a gene or something the body, the moon causes the transformation similar to how the Sun burns vampires.

 Yes, me too. It makes no sense that it will become a vampire or a witch for that matter but vampire traits is possible (given the fact we know now). Knowing Klaus however he'll want his child to at least kill once so that he can transform, I don't think Klaus wants his child as a human, either hybrid or werewolf.