genotype

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genotype

(jēn`ətīp'): see geneticsgenetics,
scientific study of the mechanism of heredity. While Gregor Mendel first presented his findings on the statistical laws governing the transmission of certain traits from generation to generation in 1856, it was not until the discovery and detailed study of the
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.

genotype (and phenotype)

the unique collection of genes an individual receives from both parents as a result of cell division (meiosis) and fusion of the ovum and sperm (fertilization). All these genes have the potential to determine, or help determine, characteristics of the individual, but not all will in fact exert an influence since they are received from both parents and the gene for a characteristic, e.g. eye colour, from one parent may be dominant over that from the other parent. The genotype therefore expresses genetic potential, and even though genes may not be expressed in the individual they will be passed on to the offspring.

While the genotype is the total genetic potential of the individual, the phenotype is the actual expression of the genes as the individual. The phenotype therefore describes the pattern of genes that have influenced the development of the individual, e.g. the gene for the individual's eye colour, but not for the eye colour not exhibited, though still carried in the genotype.

Genotype

 

the sum total of all the genes localized in the chromosomes of a given organism. In a broader sense, the genotype is the sum total of all the hereditary factors of the organism, both nuclear (genome) and nonnuclear, or extrachromosomal (that is, cytoplasmic and plastid hereditary factors). The term was introduced by the Danish biologist W. Johannsen in 1909.

The genotype is the carrier of hereditary information, transmitted from generation to generation. It is the system that controls the development, structure, and vital activity of the organism, that is, the sum total of all the characteristics of the organism—its phenotype. The genotype is an integral system of interacting genes, so that the expression of each gene depends on the genotypic environment in which it is located. For example, the red coloration of the blossoms in some varieties of the sweet pea arises only during the simultaneous presence in the genotype of dominant alleles of two different genes, whereas separately each of these alleles causes a white coloration of the blossoms. The interaction of the genotype with the complex of factors of the internal and external environment of the organism cause a phenotypic manifestation of characteristics. The coloration of the fur of rabbits of the so-called Himalayan line serves as an example of the influence of the environment on phenotypic manifestation of genotype. Although they have one and the same genotype, these rabbits when raised in cold temperatures have black fur; when raised in moderate temperatures they have the Himalayan coloration (white with black noses, ears, feet, and tail). When raised in hot temperatures they have white fur. The offspring of these three groups of animals inherit not one immutable coloration of fur but, rather, the ability to produce a particular coloring depending on environmental conditions. Thus, in a general sense, it is more correct to say that the genotype determines the inheritance not of concrete traits but of the norm of reaction of the organism to all possible conditions of the environment. Some genes are in an active state at certain times in an individual’s development, while other genes may become active at other times; therefore, in ontogenesis the genotype functions as a changeable mobile system.

The term “genotype” is sometimes used in a much narrower sense to denote simply groups of genes or even individual genes whose inheritance is being studied. For example, the splitting offspring of the monohybrid cross AA x aa are commonly said to have genotypes AA, Aa, and aa, and the possible differences based on other genes between corresponding individuals (or groups of individuals) is disregarded.

V. I. IVANOV

genotype

[′jē·nə‚tīp]
(genetics)
The genetic constitution of an organism, usually in respect to one gene or a few genes relevant in a particular context.
(systematics)
The type species of a genus.
References in periodicals archive ?
For these conversions, we used the LDLc distribution by APOE genotype for the specific population subsample in which the threshold was being estimated.
This finding lends itself to the conclusion that the interaction between TBI, OSA, and APOE genotype may be more complex than originally thought.
APOE genotype and an ApoE-mimetic peptide modify the systemic and central nervous system inflammatory response.
Green and his colleagues then randomized 162 asymptomatic adult children of people with AD from the Boston area to either receive a risk assessment based on age, family history, gender, and disclosure of APOE genotype or one based only on age, family history, and gender.
Kristine Yaffee, the primary author of this study, published in Neurology (2000;54:1948-53), doesn't suggest that women go out and have their APOE genotype tested just yet.
The research team developed graphics and language to facilitate communication of APOE genotype and numerical risk estimate.
However, a third study found no such effect based on APOE genotype in brain injury patients (Brain 2004;127:2621-8).
Atherotech provides clinicians with a single source for the VAP Cholesterol Test and more than a dozen cardiovascular and metabolic tests, including C-Reactive Protein (hsCRP), LpPLA2, apoE genotype, NT-proBNP, cystatin C, T3 and T4 when TSH is abnormal, plus gamma-glutamyl transferase (GGT), a recognized cardiovascular risk biomarker.
Of interest, clearance of TRLs is a function of the apoE genotype; patients with the E4 and E2 alleles, demonstrate slower clearance and increased concentrations of remnants as well as increased CVD risk (17), so there might be a differential association with apoE genotypes.
Cardiometabolic testing available through Atherotech includes C-Reactive Protein (hsCRP), LpPLA2, apoE genotype, NT-proBNP, Cystatin-C, T3 and T4 when TSH is abnormal, plus gamma-glutamyl transferase (GGT), a recognized cardiovascular risk biomarker.
APOE genotype as a risk factor for ischemic cerebrovascular disease: a meta-analysis.