language-icon Old Web
English
Sign In

Genotype

The genotype is the part of the genetic makeup of a cell, and therefore of any individual, which determines one of its characteristics (phenotype). The term was coined by the Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1903. The genotype is the part of the genetic makeup of a cell, and therefore of any individual, which determines one of its characteristics (phenotype). The term was coined by the Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1903. Genotype is one of three factors that determine phenotype, along with inherited epigenetic factors and non-inherited environmental factors. Not all organisms with the same genotype look or act the same way because appearance and behavior are modified by environmental and growing conditions. Likewise, not all organisms that look alike necessarily have the same genotype. One's genotype differs subtly from one's genomic sequence, because it refers to how an individual differs or is specialized within a group of individuals or a species. So, typically, one refers to an individual's genotype with regard to a particular gene of interest and the combination of alleles the individual carries (see homozygous, heterozygous). Genotypes are often denoted with letters, for example Bb, where B stands for one allele and b for another. Somatic mutations which are acquired rather than inherited, such as those in cancers, are not part of the individual's genotype. Hence, scientists and physicians sometimes talk about the genotype of a particular cancer, that is, of the disease as distinct from the diseased. An example of a characteristic determined by a genotype is the petal color in a pea plant. The collection of all genetic possibilities for a single trait are called alleles; two alleles for petal color are purple and white. Any given gene will usually cause an observable change in an organism, known as the phenotype. The terms genotype and phenotype are distinct for at least two reasons: A simple example to illustrate genotype as distinct from phenotype is the flower colour in pea plants (see Gregor Mendel). There are three available genotypes, PP (homozygous dominant), Pp (heterozygous), and pp (homozygous recessive). All three have different genotypes but the first two have the same phenotype (purple) as distinct from the third (white). A more technical example to illustrate genotype is the single-nucleotide polymorphism or SNP. A SNP occurs when corresponding sequences of DNA from different individuals differ at one DNA base, for example where the sequence AAGCCTA changes to AAGCTTA. This contains two alleles : C and T. SNPs typically have three genotypes, denoted generically AA Aa and aa. In the example above, the three genotypes would be CC, CT and TT. Other types of genetic marker, such as microsatellites, can have more than two alleles, and thus many different genotypes. Penetrance is the proportion of individuals showing a specified genotype in their phenotype under a given set of environmental conditions.

[ "Gene", "Caliciviridae Infections", "ADRA2B Gene", "Glutathione S transferase GSTT1", "Ningxiang pig", "Glecaprevir / pibrentasvir" ]
Parent Topic
Child Topic
    No Parent Topic