Mendelian traits behave according to the model of monogenic or simple
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
inheritance in which one gene corresponds to one trait.
Discrete
Discrete may refer to:
*Discrete particle or quantum in physics, for example in quantum theory
* Discrete device, an electronic component with just one circuit element, either passive or active, other than an integrated circuit
* Discrete group, ...
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
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
,
allele
An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule.
Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...
s 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
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...
. 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
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...
,
codominance,
genetic linkage
Genetic linkage is the tendency of Nucleic acid sequence, DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two Genetic marker, genetic markers that are physically near ...
,
environmental effects, and quantitative contributions from a number of genes (see:
gene interactions,
polygenic inheritance
A quantitative trait locus (QTL) is a locus (section of DNA) that correlates with variation of a quantitative trait in the phenotype of a population of organisms. QTLs are mapped by identifying which molecular markers (such as SNPs or AFLPs) co ...
,
oligogenic inheritance).
OMIM
Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of human genes and genetic disorders and traits, with a particular focus on the gene-phenotype relationship. , approximately 9,000 of the over 25,000 entries in 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 Genotyping is the process of determining differences in the genetic make-up (genotype) of an individual by examining the individual's DNA sequence using bioassay, biological assays and comparing it to another individual's sequence or a reference seq ...
, they were used as
genetic marker
A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can ...
s in medicolegal practice, including in cases of disputed
paternity.
Human traits with probable or uncertain simple inheritance patterns
See also
*
Polygenic inheritance
A quantitative trait locus (QTL) is a locus (section of DNA) that correlates with variation of a quantitative trait in the phenotype of a population of organisms. QTLs are mapped by identifying which molecular markers (such as SNPs or AFLPs) co ...
*
Trait
*
Gene interaction
*
Dominance
*
Homozygote
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mos ...
*
Heterozygote
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mos ...
References
External links
OMIM Online Mendelian Inheritance in ManINTERSNP- a software for genome-wide interaction analysis (GWIA) of case-control and case-only SNP data, including analysis of quantitative traits.]
GeneticInteractions.org
{{genarch
Human genetics
Classical genetics