[Nobody's Confidant (OP)]

There are many movies and video games about mutation making people zombies or making a person stronger...but is this possible?

Could you malform a number of cells to make it so your arm is super strong, at the loss of part of your humanity?

[rosy]

No. Will that do?

Sorry. I shouldn't be flippant. The cell is amazing, if you think people are complicated just you go away and read up on molecular cell biology. The existence of cells is soooo much more amazing than the existence of mammals (well, the existence of mammals once cells exist)!
Hmm, anyway...
All these films about people being zapped with radiation so that they suddenly get stronger (or whatever) are just so much utter drivel (tho' entertaining, the good ones..). If you zapped a group of cells with a lot of radiation, or chemicals, or whatever, they would almost certainly damage the DNA of some of the cells. One might in some way be altered so that it makes a muscle protein that's in some way better (stronger or whatever), but many more will be altered so that they can no longer function and the cells will die (or become cancerous).
As to losing some of their humanity... well, I guess if their brains got poisoned or whatever they might get some kind of brain damage resulting in personality changes, which might count (some types of brain damage can do pretty wierd things sometimes...).

[another_someone]

The problem, as I see it, is that it is not enough to make the arm stringer - if muscle is generating more energy, then the bones and the ligaments must be able to manage those extra forces, and the blood supply must be able to deliver fuel to the muscle in sufficient amount to maintain the muscle output, and take waste away from the muscle so the muscle does not poison itself.

Clearly, some increase in muscle bulk is possible to some extent - to the extent that has been shown with the use of illegal drugs used in sports.  Take it much beyond that and the rest of the body wont stand the strain.  If a muscle has enough strength to snap bone, then it will also snap the supporting bones on which it is anchored, unless those bones are also reinforced.

As for making people zombies - what do you regard to be a zombie?

http://en.wikipedia.org/wiki/3-quinuclidinyl_benzilate#Clinical_effects

The patient is often disoriented to time and place. Disturbances in judgment and insight appear. The patient may abandon socially imposed restraints and resort to vulgar and inappropriate behavior. Perceptual clues may no longer be readily interpretable, and the patient is easily distracted and may have memory loss, most notably short-term memory. In the face of these deficits, the patient still tries to make sense of his environment and will not hesitate to make up answers on the spot to questions that confuse him. Speech becomes slurred and often senseless, and loss of inflection produces a flat, monotonous voice. References become concrete and semiautomatic with colloquialisms, clichés, profanity, and perseveration. Handwriting also deteriorates. Semiautomatic behavior may also include disrobing (perhaps partly because of increased body temperature), mumbling, and phantom behaviors such as constant picking, plucking, or grasping motions ("woolgathering" or carphology).

How close is that to your definition of a zombie?

[Nobody's Confidant (OP)]

Pretty close, thanks.

Thanks people! I understand perfectly now!

[Quantum_Vaccuum]

You can become mutated by birth, so you can come out of your mom with 3 arms, or 1 working eye, but these mutations are very very rare, the normal mutations are like, decreased hair growth, or vise versa, or cross eyed mutation, like i had when I was born before I got eye surgery. But anyway, the helpful mutations don't normaly occur without weakining another part of your body, for example, you could have more strength and athletic skills, but become less smart and loose some learning ability