Do all Uchihas have fire nature chakra?

Question

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)

Answer 1

Yes, all Uchiha have their natural affinity towards Fire. It is like a default setting, to put it in simpler terms. In the article you provided, it also states that:

In general, every person's chakra has an affinity towards one of the five basic nature transformations.

Being the descendants of Indra Ōtsutsuki it is logical to think that every Uchiha in the clan would hold a natural affinity towards the Fire element:

[Indra] could use Yin Release, and, in the anime, was shown skilled in the usage of Fire and Lightning Release since his childhood.

Also, from the wiki article on the Uchiha Clan which might suggest that only true Uchiha have that affinity towards fire:

They also have an especially potent chakra quality as well as a natural affinity for the fire nature transformation; Uchiha are not truly considered adults until they can successfully perform the Fire Release: Great Fireball Technique.

Answer 2

Ero Sennin's answer is very good. I would also like to add that the Uchiha all use the Goukakyuu no jutsu. The official wiki states that:

The Uchiha clan uses this technique as a "coming of age" rite

This is just further proof that that the Uchiha all have a fire affinity, or else, this would not be a thing.