Alleles and Loci

alleles (short for allelomorphs)   Each gene is able to occupy only a particular region of chromosome, its locus. At any given locus there may exist, in the population, alternative forms of the gene. These alternatives are called alleles of one another.

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locus   The position on a chromosome occupied by a gene (or a set of alternative alleles). For instance, there might be an eye-colour locus, at which the alternative alleles code for green, brown, and red.

Dawkins didn't see how the concepts translated to memetics (see Another View), but I think I do, at least in some very simple cases. The trick is to look for memes that are incompatible with one another, that can't coexist.

• Strategies for a given situation are alleles. If you're involved in an iterated prisoner's dilemma, you can cooperate all the time, or play “tit for tat”, but you can't do both, you have to have one strategy. In other words, you can turn the other cheek, or retaliate—see The Thought. Alternative strategies are also mentioned in Some Memes for Oni.
• Beliefs about a given subject are alleles. Regarding abortion, for example, you can be pro-choice, or pro-life, or hold some more nuanced view, but you can't do more than one at the same time.

In addition to individual memes, you can look for clusters of memes that are incompatible with one another. At some point, though, as the clusters get larger and larger, they start to look less like different alleles competing for the same locus and more like different organisms competing for the same ecological niche.

Anyway, whether alleles or organisms, beliefs about the fundamental nature of the universe are my favorite example of incompatible clusters. In the Western tradition, such beliefs have tended to reduce to beliefs about God—you're either some variety of theist, or an atheist. In the Eastern tradition, though, there are incompatible clusters for the same locus that just don't say anything about God one way or the other, like Buddhism and Taoism.