Mendelian traits in humans
Mendelian traits in humans concerns how, in Mendelian inheritance, a child receiving a dominant allele from either parent will have the dominant form of the phenotypic trait or characteristic. Only those that received the recessive allele from both parents, known as zygosity, will have the recessive phenotype. Those that receive a dominant allele from one parent and a recessive allele from the other parent will have the dominant form of the trait. Purely Mendelian traits are a tiny minority of all traits, since most phenotypic traits exhibit incomplete dominance, codominance, and contributions from many genes.
The recessive phenotype may theoretically skip any number of generations, lying dormant in heterozygous "carrier" individuals until they have children with someone who also has the recessive allele and both pass it on to their child.
These traits include:
- Wet (dominant) or dry (recessive) earwax - dry is found mostly in Asians and Native Americans
- Albinism (recessive)
- Brachydactyly (shortness of fingers and toes)
- Blood type
- Lactase persistence (dominant)
- Sickle-cell disease
May be Mendelian but there is conflicting evidence:
Traits previously believed to be Mendelian
- Eye color
- Hair color
- Morton's toe
- Tongue rolling
- Ability to taste phenylthiocarbamide (dominant) - largely determined by a single gene, TAS2R38, with two common alleles, though there are 8 possible haplotypes Because it is not a trait where the dominant tastes and the recessive cannot, but rather a continuous gradient in ability to detect PTC, it is not a real example of a simple mendelian trait. This is best exemplified by the fact that two non-tasters (recessive trait) can, in fact, have a child that can taste PTC (dominant trait). 
- Widow's peak (allele)
- Detached (dominant) or attached (recessive) earlobes
- Hitchhiker's thumb (recessive)
- Human genetic variation
- Human genetic clustering
- Human inbreeding in royal blood lines
- Kim, U. K., E. Jorgenson, H. Coon, M. Leppert, N. Risch, and D. Drayna. 2003. Positional cloning of the human quantitative trait locus underlying taste sensitivity to phenylthiocarbamide. Science 299: 1221-1225
- McDonald, J.H. 2011. Myths of Human Genetics. University of Delaware. http://udel.edu/~mcdonald/mythptc.html
- Mange, Elaine J.; Mange, Arthur R. (1999). Basic Human Genetics (second ed.). Sunderland (MA): Sinauer. ISBN 0-87893-497-9. Lay summary (16 October 2010).
- Speicher, Michael R.; Antonarakis, Stylianos E.; Motulsky, Arno G., eds. (2010). Vogel and Motulsky's Human Genetics: Problems and Approaches. Heidelberg: Springer Scientific. doi:10.1007/978-3-540-37654-5. ISBN 978-3-540-37653-8. Lay summary (4 September 2010).