OK So in this novel, Anna is created to produce an exact match of white blood cells for her older sister Kate. Anna feels like her sole purpose is to provide for her sister: that her parents don't even love her.
This brings up a pretty sad point about medical science. Is it wrong to conceieve a child as a donor? I'd say yes.

I read this book as well. I think it is a really tough issue. I mean, on one hand, you have a dying child, and it's got to be pretty hard to just sit and watch your kid die. But, the child born to be a donor is still a person with rights. And if the first child died, they might feel as though their parents no longer want them because they don't serve a purpose anymore. And they might not feel as if they are truly wanted or loved. So in the long run, I don't think it is fair to the child to have them born just to be a donor for another one.

Suppose it's possible through some manner of genetic manipulation for a child with no higher brain functions, thus essentially no consciousness or mind, to be conceived. Would it be immoral for such a child to be raised and cared for solely to serve as an organ bank?

If you want to take it a step further, consider a clone (presuming cloning technology is such that clones are conceived without any of today's unfortunate side-effects) of the child in question that is identical in every way, save the lack of any higher brain functions. The clone is, again, essentially spare parts for the original child.

Still immoral?

Well, yeah. If you have a kid just to save the other, it's almost like saying that they DO love the other more. Of course, if the younger one, the one born to be a donor, loved the older very much and WANTED to donate, yeah! That's awesome!