Bitter taste gene discussion

Ever since they passed around that little tab in school to see if one could taste bitter, I've been curious about this. I wasn't there that day, and never got a chance to do it. The first time I tasted tonic water and grapefruit, I thought my mouth was going to turn inside out. Others love both. That never seemed to go along with my love for broccoli and tolerance for Brussels's sprouts.

So, I got my 23 and Me results, and so it now makes perfect sense. The results are what one would expect from my raw data. Unfortunately, it did not test for Stevia. As hard as I've tried to switch from Splenda, I cannot get over that taste just like the author of this article who said,

quote:

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I love a good, dark roast, cup of coffee, and Brussels sprouts and cabbage taste great. It turns out that I can’t taste the bitter compound in them, but the majority of people can. On the other hand, I have yet to find a brand of stevia that I like because of the awful aftertaste. It turns out that I am genetically more sensitive to the bitter taste of steviol.

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Can this account for the vast difference in the way people taste beer? Are there other foods/drinks this applies to? I had no idea umami was another taste.