Random thought: If a gene were discovered which was thought to (through whatever mechanism) be responsible for people holding racist views, what do you think the reaction to that would be?
Pretty sure it's scientifically impossible; I'm more interested in the philosophical mindfuck it gives me when I contemplate it. For example, I'd assume there would be people who would push for this knowledge to be used for eugenics in some form or another, but they'd likely be the same people who had the gene in the first place.
I'm also half-wondering if Petermac or someone will pop in and say "Actually, one was found, and [FIB with info]." 
I've not heard of one, but I think racism almost certainly has a strong genetic component and that it arises from a fairly fundamental aspect of animal psychology. When you strip away all the culturally-derived fluff, what you're left with is basically a kinship recognition and response system, which you'll find in any social species, from ants and bees to antelope and bonobos. These systems work by assessing the relatedness of other organisms and then producing a behavioral response, which is usually some form of aggression towards members of the same species that are too distantly related, or that are members of a different colony or herd.
Humans are a lot more nuanced than other species, and can recognise both genetic relatedness and political relatedness arising from group memberships (family/tribe/nation/race/religion) in fine-grained detail, and their higher cognitive functions give them more control over their instincts, but they still have this system in their heads that tweaks their emotions and twists their perception according to it's assessments of self and other, and subject to as much individual variability as other mental functions.
Speaking from personal experience, if I'm walking along the street and I see someone coming towards me who looks African or Asian, it makes me feel even more uncomfortable than I usually feel when I see people walking towards me. Sometimes I even feel a chill and a sudden squirt of adrenaline, but there's no rational reason for it; I'm not afraid of them or have any hatred towards them that might explain it, and it's something I noticed about myself back when I was a kid. I used to feel inwardly embarrassed at myself for reacting that way, but as far as I'm able to tell, it's just my kinship recognition and response system pulling my strings and trying to get me to howl and throw poo from the treetops. It's similar to the stomach flutter that I get (or used to get, at any rate) on seeing women that I was attracted to; same sudden squirt of adrenaline, but a different emotional response coming from a different but similarly ancient and fundamental pattern recognition and response system that's wired according to a different set of genetic instructions.
, and quacks like a 