Mendelian traits in humans

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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]
Heredity of phenotypic traits: Father and son with prominent ears and hair whorl.
An example of the codominant inheritance of some of the four blood groups.

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.

Genes that do not follow Mendelian genetics include the human Y chromosome which is passed virtually unchanged from father to son. Similarly, the mitochondrial DNA (mtDNA) comes only from the mother and is given to both male and female children. Epigenetic modifications, linked genes, and duplicated genes elsewhere in the genome will also lead to a non-mendelian inheritance of traits.

Examples[edit]

These traits include:

Questionable traits[edit]

May be Mendelian but there is conflicting evidence:

Non-Mendelian Traits in Humans[edit]

Physical Mendelian Traits in Humans[edit]

Blood group inheritance[edit]

Blood from the ABO system is not mendelian because multiple alleles are required from each parent (co-dominant). However the Rhesus factor is truly mendelian because only one allele is inherited from each parent. Rh factor is an antigen on the red blood cell of many people's blood. A positive Rh factor is dominant (presence of antigen) and a negative Rh is recessive (lack of antigen).[14]

United States Blood Type Frequency[15]
Blood Type and Rh United States Frequency % of U.S. Population
O+ 1 in 3 37.4%
O- 1 in 15 6.6%
A+ 1 in 3 35.7%
A- 1 in 16 6.3%
B+ 1 in 12 8.5%
B- 1 in 67 1.5%
AB+ 1 in 29 3.4%
AB- 1 in 167 0.6%
The United States has a heavily skewed distribution of blood types. The majority of the population has a positive Rh factor, with most of these people bing A and O blood types.

Blood groups that children may inherit from their parents.[16][17]

Blood Type Inheritance
Father's Blood Type
Mother's Blood Type A B AB O
A A or O A, B, AB, or O A, B, or AB A or O
B A, B, AB, or O B or O A, B, or AB B or O
AB A, B or AB A, B, or AB A, B, or AB A or B
O A or O B or O A or B O

See also[edit]

References[edit]

  1. ^ a b "Inheritance of Sickle Cell Anaemia – Sickle Cell Society".
  2. ^ "Myths of Human Genetics: Earwax".
  3. ^ Sanfilippo syndrome
  4. ^ "OMIM Entry – 304300 – CYANIDE, INABILITY TO SMELL".
  5. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  6. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  7. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  8. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  9. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  10. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  11. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  12. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  13. ^ kazilek (2010-07-20). "Human Traits". askabiologist.asu.edu. Retrieved 2018-11-29.
  14. ^ "Human Blood: Rh Blood Types". www2.palomar.edu. Retrieved 2018-11-30.
  15. ^ "Blood Type Frequency - Lancaster General Health". www.lancastergeneralhealth.org. Retrieved 2018-11-30.
  16. ^ "ABO inheritance patterns". Inheritance patterns of blood groups. Australian Red Cross Blood Service. Retrieved 30 October 2013.
  17. ^ "ABO blood group system". Abobloodtypes.webnode.com. Retrieved 2015-02-02.

Further reading[edit]

External links[edit]