# Myths of Human Genetics - Author: **John H. McDonald** - Document Tags: [[ear wax]] - [URL link](https://udel.edu/~mcdonald/mythearwax.html)  ## Highlights - the allele for wet earwax is dominant over the allele for dry earwax ([View Highlight](https://read.readwise.io/read/01hwygb1kvh22mszwsxea37c87)) --- - You can do a Google Images search for "earwax" if you want to get grossed out, but I'd rather look at kittens ([View Highlight](https://read.readwise.io/read/01hwygc9x7khmbvf3mx8a4nbgg)) --- - Wet earwax is sticky and yellowish brown to dark brown in color, while dry earwax is crumbly and gray to tan ([View Highlight](https://read.readwise.io/read/01hwygcq4vyfa7ex9pc2yrhn3m)) --- - The allele for wet earwax has a G at site 538 of the coding region, which causes a glycine at position 180 in the amino acid sequence; most dry alleles have an A at site 538, coding for arginine ([View Highlight](https://read.readwise.io/read/01hwyge374r9dpve6c37rhpvg5)) --- - There is another, less common allele, a deletion of 27 nucleotides in exon 29, that also causes dry earwax ([View Highlight](https://read.readwise.io/read/01hwygeb1bj77caqtg66aqpefj)) --- - The allele for dry earwax has frequencies close to 100% in people from northern China and Korea, is intermediate in people from Japan, southern Asia, and the Americas, is uncommon in Europe, and is almost completely absent in Africa ([View Highlight](https://read.readwise.io/read/01hwygg0d70q10d6c5ynhsenw5)) --- - There are very few polymorphisms in the human genome that show this much difference in allele frequency between one geographic area and another ([View Highlight](https://read.readwise.io/read/01hwyggbptfcyx9qvf86vt60qx)) --- - with dry earwax individuals having a relative fitness about 1 percent higher than wet earwax individuals ([View Highlight](https://read.readwise.io/read/01hwygh3qp8d8k8g02sxb73dgx)) --- - Wet earwax is associated with warmer areas in Europe, Asia and the Americas (Ohashi et al. 2011), so there seems to be something about cooler climates that favors the dry earwax allele. ([View Highlight](https://read.readwise.io/read/01hwyghfp02gg2xcc9dw9rwcfw)) --- - Earwax and body odor ([View Highlight](https://read.readwise.io/read/01hwyght8fdjje5f9nncp0c1ef)) --- - There are two kinds of sweat glands: eccrine sweat glands, which are found throughout the skin, and apocrine sweat glands, which are found in the armpits and groin ([View Highlight](https://read.readwise.io/read/01hwygkbdaj3j3hqa1j8dess35)) (Tags: [[sweat glands]]) --- - Apocrine sweat contains proteins and lipids; when bacteria on the skin metabolize apocrine sweat, they produce body odor. The earwax glands (ceruminous glands) are a form of apocrine gland. ([View Highlight](https://read.readwise.io/read/01hwygjw8yqcj7tsmx18ck6yxf)) --- - wet earwax has long been associated with greater body odor ([View Highlight](https://read.readwise.io/read/01hwygmk5sn3pzhsr6tkgw4hj4)) --- - found that several compounds that are precursors for body odor are absent or in lower concentrations in sweat from people with the dry earwax genotype. ([View Highlight](https://read.readwise.io/read/01hwygnfa9cf5fp4qvwrbcng4q)) --- - did not find a significant difference in the frequency of wet earwax. ([View Highlight](https://read.readwise.io/read/01hwygqghe7fp8nezm4450yajm)) --- - found that women with dry earwax were less likely to produce colostrum (the breast milk produced around childbirth), and those who did produced smaller volumes than women with wet earwax. ([View Highlight](https://read.readwise.io/read/01hwygt5et6ez2e1tdcfk03hgv)) ---