Well blood i'd think is ok......no one really wants someone elses blood unless they NEED it.....so that means they are in critical condition... (some athletes used to store their blood, then before a game, have the blood re-injected so they are able to carry more oxygen......but they use their own blood.....i'm going off topic....there was a point to that)
The only reason i've heard people question if donating organs is wrong is that we are suppose to return to the earth when we die. Sooo if you give your heart away to someoen, you can't return it to the earth. But I've heard that this is not somethign to worry about and its ok.
I'm biased i guess towards genetic engineering being ok, because i do some of that.
But in all honesty...lets say a plant..you can breed a plant to get the result you want, but you have to wait maybe 50 years of constant breeding.......or you can try genetic engineering....and in a few months you find out if it worked or not. Now on the chemical level, the genetic engineered plant and the plant that was bred for the desired result will be identical. You'll only be able to know if its engineered if someone told you it was.
Some say only god can decide about things in nature....well i say if he was going to prevent the result from happening naturally, the genetic engineering will also fail.
Also we are told that every disease has a cure, but we have to find it....and well, genetic engineering could cure some of the diseases...so it think that fits the description.
and i'm unsure about cloning....i'm mixed on my own personal feelings.