Alleles

[curious dave] wrote, in part:

You can talk about specific allele frequencies, though– F’rexample, Asian people tend to have the allele for hard earwax, whilst Europeans tend to have soft.

I have a fondness for whenever Davo says “F’rexample.” (I think I might steal that for my own devious uses, if it’s all right with you, Davo.) And of course you brought up excellent points about our antiquated ideas of race as a term of any usefulness in the age of modern science.
[Sarea] asks in response in another note:
And what does the above noter mean about "Asian people tend to have the allele for hard earwax". What’s allele?
Cos I’m asian (not pure anyway) but still an asian. And I am curious to know what he meant.
That’s a great question! I was quite ignorant of the word allele and its meaning until the embarrassing age of 20, I’m afraid to say. The story of my miserable childhood is another long tale altogether, and one I won’t delve into tonight, but let it suffice to say I was home schooled and didn’t learn anything about biology until college.
So I encountered allele for the first time in an Introduction to Human Origins class, from which I still possess the textbook a decade later. I suppose I could just as easily Google the answer and quote you verbatim from Wikipedia, but this is more fun.
The textbook in question, Understanding Physical Anthropology and Archaeology by Turnbaugh, Jurmain, Kilgore, and Nelson (8th ed., Wadsworth, 2002), states:
A gene is a segment of DNA that directs the production of a specific protein or part of a protein. Furthermore, the location of a gene on a chromosome is its locus (pl., loci). At numerous genetic loci, however, there is more than one possible form of the gene, and these variations of genes at specific loci are called alleles. Therefore, alleles are alternate forms of a gene that can direct the cell to produce slightly different forms of the same protein and, ultimately, different expressions of traits.
So, to use Davo’s example, there is presumably a specific genetic locus whose alleles that dictates the hardness or softness of earwax in humans. The allele frequency for hard earwax is higher with Asian people, and allele frequency for soft earwax is higher for Europeans.
Another example is from Gregor Mendel: plant height in garden peas is controlled by two different alleles at one genetic locus. The allele that determines that a plant will be tall is dominant to the allele for short.
According my book, currently, more than 4,500 human traits are known to be inherited according to simple Mendelian principles. Mendelian traits are controlled by alleles at one genetic locus. F’rexample, several blood group systems, such as ABO, function this way.
The reason why the word allele should have major significance, if you’re still reading by this point, is that it is involved in the definition of evolution. Simply put, evolution is a change in allele frequency from one generation to the next. This particular concept was one of the most significant ideas that I ever learned and it changed my life.
Actually, the idea of evolution through the process of natural selection is one of the most important ideas humankind has ever had. Thank you very much, Mr. Darwin and Mr. Wallace.