No, you are not a mutant McGrath. "Nicotinic receptors" are not mutations at all, but specific proteins on the surface of nerve cells which are there to receive a vital chemical in the brain called acetycholine. This chemical, called a neurotransmitter, carries information from one nerve cell to another.
Certain types of acetycholine receptors also react with nicotine. In fact, it was through experiments with nicotine that they were discovered in the first place - hence the name "nicotinic receptors". They occur naturally in all humans and most animals - 17 specific genes have been linked to them so far. With repeated exposure to nicotine, these receptors increase in size and number.
Recent experiments with mice show that when the number of a specific type of nicotinic receptor is reduced through genetic alteration, the mice do not become addicted to nicotine. Under normal genetic conditions, mice become addicted to nicotine just as humans do.