Mendelian traits in humans

Mendelian traits in humans are human traits that are substantially influenced by Mendelian inheritance. Most – if not all – Mendelian traits are also influenced by other genes, the environment, immune responses, and chance. Therefore no trait is purely Mendelian, but many traits are almost entirely Mendelian, including canonical examples, such as those listed below. Purely Mendelian traits are a minority of all traits, since most phenotypic traits exhibit incomplete dominance, codominance, and contributions from many genes. If a trait is genetically influenced, but not well characterized by Mendelian inheritance, it is non-Mendelian.

Autosomal dominant

A 50/50 chance of inheritance.

Sickle-cell disease is inherited in the autosomal recessive pattern. When both parents have sickle-cell trait (carrier), a child has a 25% chance of sickle-cell disease (red icon), 25% do not carry any sickle-cell alleles (blue icon), and 50% have the heterozygous (carrier) condition.^[1]

If one parent has sickle-cell anaemia and the other has sickle-cell trait, then the child has a 50% chance of having sickle-cell disease and a 50% chance of having sickle-cell trait.^[1]

An example of the codominant inheritance of some of the four blood groups.

Examples

• Albinism (recessive)^[2]: 53
• Achondroplasia^[2]: 53
• Alkaptonuria^{[2]: 53, 263}
• Ataxia telangiectasia^[2]: 53
• Brachydactyly (shortness of fingers and toes)^[2]: 53
• Cataracts
• Colour blindness^[2]: 53 (monochromatism, dichromatism, anomalous trichromatism, tritanopia, deuteranopia, protanopia)
• Duchenne muscular dystrophy^[2]: 53
• Ectrodactyly^[3]
• Ehlers–Danlos syndrome^[2]: 53
• Fabry disease^{[citation needed]}
• Galactosemia^[2]: 53
• Gaucher's disease^{[citation needed]}
• Haemophilia
• Hereditary breast–ovarian cancer syndrome^{[citation needed]}
• Hereditary nonpolyposis colorectal cancer^{[citation needed]}
• HFE hereditary haemochromatosis
• Huntington's disease^[2]: 53
• Hypercholesterolemia^[2]: 53
• Krabbe disease^{[citation needed]}
• Lactase persistence (dominant) ^[4]
• Leber's hereditary optic neuropathy^{[citation needed]}
• Lesch–Nyhan syndrome^[2]: 53
• Marfan syndrome^[2]: 53
• Niemann–Pick disease^{[citation needed]}
• Phenylketonuria^[2]: 53
• Porphyria^[2]: 53
• Retinoblastoma^{[citation needed]}
• Sickle-cell disease^[2]: 53
• Sanfilippo syndrome^{[citation needed]}
• Tay–Sachs disease^[2]: 53
• Wet (dominant) or dry (recessive) earwax^[5]

Non-Mendelian traits

Most traits (including all complex traits) are non-mendelian. Some traits commonly thought of as Mendelian are not, including:

• Eye Color
• Psychiatric diseases
• Hair color
• Height^[6]

References

1. "Inheritance of Sickle Cell Anaemia". Sickle Cell Society. 13 July 2014. Archived from the original on 2018-03-27. Retrieved 2015-12-29.
2. Klug WS, Cummings MR, Spencer CA, Palladino MA (2012). Essentials of Genetics. Pearson. ISBN 978-0-321-80311-5.
3. Sowińska-Seidler A, Socha M, Jamsheer A (February 2014). "Split-hand/foot malformation - molecular cause and implications in genetic counseling". Journal of Applied Genetics. 55 (1): 105–115. doi:10.1007/s13353-013-0178-5. PMC 3909621. PMID 24163146.
4. Hollfelder N, Babiker H, Granehäll L, Schlebusch CM, Jakobsson M (April 2020). "The genetic variation of lactase persistence alleles in northeast Africa". bioRxiv 10.1101/2020.04.23.057356.
5. McDonald JH (16 September 2013). "Earwax". Myths of Human Genetics. Baltimore: Sparky House Publishing.
6. "Non-Mendelian Genetics". Untamed Science. Retrieved 2018-12-10.

Further reading

• Mange EJ, Mange AR (1999). Basic Human Genetics (second ed.). Sunderland (MA): Sinauer. ISBN 978-0-87893-497-3.
• Simpson SA (November 1999). "Basic Human Genetics". Heredity (Review). 83 (5) (2nd ed.): 635. doi:10.1038/sj.hdy.6886484.
• Speicher MR, Antonarakis SE, Motulsky AG, 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. S2CID 89318627.

External links

• OMIM Online Mendelian Inheritance in Man
• Myths of Human Genetics