But, MP, the difference is that a mouth cell is a mouth cell which has the functions of a mouth cell.
A fertilized ovum is a new individual whose sole purpose and reason for being is continued development and birth.
It was created from the union of two gametes (do I remember my HS/college biology correctly?) whose purpose is union with its opposite to form a new human being.
That fertilized ovum, if left in its "natural habitat", a woman's uterus, fully develops and is born.
That mouth cell might become another person through the artificial and unnatural method of cloning.
Some serious and relevant distinctions.
I do not have to win a debte to state that life begins at conception or that abortion is wrong. However, since you cannot say when life begins, is your conscience clear that killing a zygote, embryo, fetus or whatever stage it may be or label it may have is not taking human life? Are you totally at peace with that?
Not all conceptions result in babies when something goes wrong. But conception is the way God designed human beings to come into the world is it not? It's not the stork that brings them, that's for sure.
I think Helen and From the Right both made good points.