Unlike most of the human traits used in classrooms to demonstrate simple genetic principles, wet vs. dry earwax actually is controlled by a single gene with (only) two alleles. The two alleles are W (for wet) and D (for dry). The W allele is dominant, so heterozygote (W;D) individuals have wet earwax, and individuals with dry earwax are all (D;D) recessive homozygotes.
This SNP can also be used to distinguish Asian ancestry.
NCBI Coffebreak Introductions:
- Ear wax (title: Don't put anything smaller than your elbow in your ear)
- Sweat (title: Roses, Noses and Underarms: how one variation in our DNA influences underarm perspiration (and ear wax)
Earwax is also used to explain heredity in the Green Brothers Crash Course Biology #9 YouTube video.