כל מחמצת לא תאכלו
שמות יב – כ
Do not eat anything that has Chametz inside, even if the Chametz is not the main ingredient.
When there is an olives worth of Chametz mixed into the amount of "half a loaf", but the Chametz is the minority. For when the Chametz is the majority, this prohibition is not needed, the regular prohibition on eating Chametz applies. When there is less than an olives worth, it is prohibited by Rabbinical law only.
Males and females.
So we remember the miracles we saw in Egypt, and especially that Hashem took us out so quick that we needed to bake our dough as Matza.
In the 3rd perek of Psachim
If one eats it
He gets Malkos, but not Kareis.
According to the Ramban
Such a mixture does get Kareis, because it is included in the standard prohibition on Chametz. He explains that this Pasuk is not a separate prohibition, rather it comes to include Chametz that was made Chametz by an external catalyst, as part of the standard prohibition.