Quote Originally Posted by AssertnFailure
That is indeed an interesting point...one that I had never really thought of much myself...
However an ability should not have to be passed down for it to be qualified as a bloodlimit. Perhaps it may be a little over-analyzing, but it seemed Haku's mother did not expect Haku to inherit her bloodlimit, even though it was a bloodlimit. Even more credible, perhaps, is the point that not all uchihas are capable of unlocking the Sharingan. So even if your parents are both uchihas, you still might not inherit their abilities. Just as the shodaime Hokage's kids didn't inhert his ability.

You could even go farther to observe a more rapid mutation/evolution effect occuring with the chakra characteristics of decendents. This happens to such a degree that certain abilities might only exist within single generations, and then could immediately be lost again through dominant/recessive relationships between their abilities and the abilities of their spouses. Considering the immense variety of distinctly unique jutsus out there, this would pretty much have to be certain.

Finally, Sandaime Kazekage's iron jutsu is a characteristic of his own natural chakra. This is why Sasori is able to harness the ability just by possessing sandaime's body. If the body makes all the difference, then what else could it be than genetic?
You make some incredibly valuable points. First off Haku's mother did not expect him to inherit her abilities because he was not a pure blood for lack of a better term, she apparently had not even considered the possibility that Haku might be able to inherit her bloodline limit without his father also possessing it.

The Uchiha’s bloodline limit seems to be in another league when compared to others. With the Hyuuga and Kaguya clans it appears that their Kekkei Genkai is a given and is automatically acquired by their children from either or both parents. The Uchiha’s abilities appear to necessitate both parents to be Uchiha’s similar to sickle cell anemia and many other genetic diseases but the offspring are only born with the potential to awaken the Sharingan. The awakening itself has special requirements, after the initial awakening there appear to be other requirements for each tomoe as evidenced by Sasuke in his battles with Haku, Lee and Naruto respectively. When the Sharingan is finally fully awakened then there are other special requirements that need to be met before the Mangekyo Sharingan can be acquired. The Sharingan also seems to be the only doujutsu that allows the user to turn it off when not in battle and the eye then returns to a “normal” state.

Kekkei Genkais as well as the Sandaime Kazekage and the Shodai Hokage’s abilities are all the result of genetic mutation and eventual evolution a subject which immensely interests me as I myself suffer from a yet to be named illness that appears to be the result of random genetic mutation within my family although I posses no superhuman abilities or positive side effects.