Mendelian traits behave according to the model of monogenic or simple gene inheritance in which one gene corresponds to one trait. Discrete traits (as opposed to continuously varying traits such as height) with simple Mendelian inheritance patterns are relatively rare in nature, and many of the clearest examples in humans cause disorders. Discrete traits found in humans are common examples for teaching genetics.
Mendelian model According to the model of Mendelian inheritance, alleles may be dominant or recessive, one allele is inherited from each parent, and only those who inherit a recessive allele from each parent exhibit the recessive phenotype. Offspring with either one or two copies of the dominant allele will display the dominant phenotype.
Very few phenotypes are purely Mendelian traits. Common violations of the Mendelian model include incomplete dominance, codominance, genetic linkage, environmental effects, and quantitative contributions from a number of genes (see: gene interactions, polygenic inheritance, oligogenic inheritance).Dobzhansky T. (1970): Mankind evolving: The evolution of the human species. Bantam Books, New York, ; .Hadžiselimović R. (2005): Bioanthropology - Biodiversity of recent man. Institute for Genetic Engineering and Biotechnology (INGEB), Sarajevo, . (in Bosnian).
OMIM (Online Mendelian Inheritance in Man)OMIM-http://www.omim.org/ is a comprehensive database of human genotype–phenotype links. Many visible human traits that exhibit high heritability were included in the older McKusick's Mendelian Inheritance in Man. Before the discovery of genotyping, they were used as genetic markers in medicolegal practice, including in cases of disputed paternity.
Human traits with probable or uncertain simple inheritance patterns
Dominant Recessive ReferencesLow heart rateHigh heart rate Widow's peak Straight hair line Facial dimples No facial dimples Ability to taste PTC, "Taster" Unable to taste PTC, "Nontaster" Unattached (free) earlobe Attached earlobeClockwise hair direction (left to right)Counter-Clockwise hair direction (right to left) Cleft chin Smooth chin Freckles No freckles Wet-type earwax Dry-type earwaxRoman nose No prominent bridgeMarfan syndromeAverage body proportions and connective tissueHuntington's diseaseNo nerve damageNormal mucous liningCystic fibrosisPhotic sneeze reflexNo light-induced sneeze reflexForged chinReceding chinWhite forelock presentNo white forelockLigamentous angustusLigamentous LaxityAbility to eat sugarGalactosemiaTotal leukonychia and Bart pumphrey syndromePartial leukonychiaAbsence of fish-like body odourTrimethylaminuriaPrimary hyperhidrosisLittle sweating in handsLactase persistenceLactose intoleranceProminent chin (V-shaped)Less prominent chin (U-shaped)Acne proneClear complexion
See also Polygenic inheritance Trait Gene interaction Dominance Homozygote Heterozygote
References
External links OMIM Online Mendelian Inheritance in Man INTERSNP - a software for genome-wide interaction analysis (GWIA) of case-control and case-only SNP data, including analysis of quantitative traits.] GeneticInteractions.org