I've read that when a certain chakra nature is hereditary for a specific clan, MOST of the members have an affinity for that chakra nature. However, it has been stated that the Uchihas are known for their fire nature chakra. Does this mean that a majority of the Uchihas had fire nature chakra, or that they all have it?
"Affinity can at times be genetic, or at least common to a particular family; most members of the Uchiha clan have an affinity towards the Fire nature." (http://naruto.wikia.com/wiki/Nature_Transformation#cite_ref-Element_1-0)