The Meanest Mom: DNA means nothing when it comes to parenting.
The instinct to describe Maria as the "adopted daughter" of Steven and Mary Beth Chapman (instead of just "the daughter") demonstrates that despite its increasing prevalence, adoption is still a mixed signifier: Parents who adopt are "heroic" and "courageous," while the children that they bring into their homes are "lucky" and "fortunate."
Until you have been touched by adoption, you do not realize that it's the other way around. For this reason, I find it strange and unfortunate that the first adjective that comes to many people's minds when describing a child born in China, Russia, Guatemala or Taiwan is "adopted." Most of us don't think twice about describing our neighbors' son as "Jim and Pam's adopted son from Guatemala," but we would never in million years describe another friend's daughter as "Allison, who was conceived in her parent's bedroom." How a child enters into a family is irrelevant. What is important is that he/she is there.
Persistent use of the term demonstrates that for most population, there is an important difference between "adopted" and "biological" child. The difference is, in part, superficial -- based on skin color or nationality. But there's also something else that is deeper and more insidious: The notion that a parent can't fully love someone who doesn't share half of his or her DNA. I wonder how these people feel about their spouses.