Conversation on the way to school yesterday morning:

Me: "I better not find out you've grown yourself a pig brother and stolen his eyeballs."

My 11-year-old: "I'd rather have two hearts. Can you live with two hearts?"

My 4-year-old from the back seat: "Oink, oink, oink."

Me: "You already have a pig sister. I better not catch you harvesting her organs."

On our morning commute, we learned about the debate over hybrid embryos — which can produce 99 percent humans. You lose 1 percent of your humanity by being implanted into a cow or rabbit egg, I guess.

Hold the flames. I'm joking. At this point, the issue is whether to use hybrid embryos to create stem cells, not to create Minotaurs, and while it might be opening Pandora's box, it could also end up saving lives.

I'm all for saving lives, but I have to confess that the possibilities — though fascinating — can be troubling, as well.

For instance, while my son got caught up in the definition of "egg," then started speculating about the potential for bizarre combinations of animal and people, I ended up brooding over the term "savior sibling."

The prospect of making a baby to save another child bothers me. I'm not saying I wouldn't consider it if one of my children had a life-threatening genetic disorder — and therefore support the research — but a child has to be a child, not the packaging for DNA.

Is that child going to be loved if it's not 100 percent human and fails to save its sibling's life?

There are times when I've watched my kids struggle in their educations and I've wondered whether I'd be willing to "rewire" their brains if there was a way to make learning easier. If I could download algebra straight into my sixth-grader's head, would I do it? He'd probably like it, just as he'd prefer to be taller, but I'm pretty darn fond of my perfectly imperfect children and wouldn't want to be fooling around with who they are.

Healthwise, though, I've vaccinated my children, given them medication and bought them glasses. I would go further than that if I needed to.

It's the next step that makes me uncomfortable. If we could make them healthier, why not stronger? If we could make them stronger, then why stop before we could also make them smarter, or more attractive?

Maybe I'm just too old-fashioned. We choose our partners. We pick how we raise our children. As best we can, we decide what to expose them to.

I just hate to think that somehow we might someday be giving up the opportunity to have the children we're meant to have in favor of the children we want to have. I'm sure that many experienced parents would agree with me that it comes out to the same thing in the end, anyway.

Then again, I'm working with the options that are available to me.

If my son has a different set of choices, I could end up grandmother to a chimera of his fancy.