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In genetics, the term dominant gene refers to the allele that causes a phenotype that is seen in a heterozygous genotype. Every person has two copies of every gene, one from mother and one from father. If a genetic trait is dominant, a person only needs to inherit one copy of the gene for the trait to be expressed. Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ...
This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...
An allele is any one of a number of viable DNA codings of the same gene (sometimes the term refers to a non-gene sequence) occupying a given locus (position) on a chromosome. ...
The phenotype of an individual organism is either its total physical appearance and constitution or a specific manifestation of a trait, such as size, eye color, or behavior that varies between individuals. ...
Heterozygotic cells are diploid or polyploid and have different alleles at a locus (position) on homologous chromosomes. ...
The genotype is the specific genetic makeup (the specific genome) of an individual, usually in the form of DNA. It codes for the phenotype of that individual. ...
Dominance/recessiveness refers to phenotype, not genotype. Consider sickle cell anemia as an example. The sickle cell genotype is caused by a single base pair change in the beta-globin gene: normal=GAG (glu), sickle=GTG (val). There are several phenotypes associated with the sickle genotype: 1) anemia (a recessive trait), 2) blood cell sickling (partially dominant), 3) altered beta-globin electrophoretic mobility (codominant), and 4) resistance to malaria (dominant). This example demonstrates that one can only refer to dominance/recessiveness with respect to individual phenotypes. Sickle-shaped red blood cells Sickle cell anemia (American English), sickle cell anaemia (British English) or sickle cell disease is a genetic disease in which red blood cells may change shape under certain circumstances. ...
A dominant gene when written in a genotype is always written before the recessive gene in a heterozygous pair. A heterozygous genotype is written Aa, not aA.
Codominance/ Incomplete Dominance - Further information: Incomplete dominance
In certain cases, a "blend" of genes will occur because neither of the two genes of a genotype are dominant over the other. As an example, in blood cells, the trait for blood type has three different alleles: type A, type B, or type i, with i being recessive. If a father passes a gamete with the allele of type A and the mother passes on type B, then codominance results, with the offspring being type AB since neither allele type dominates the other. It has been suggested that this article or section be merged with dominance relationship. ...
Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ...
An allele is any one of a number of viable DNA codings of the same gene (sometimes the term refers to a non-gene sequence) occupying a given locus (position) on a chromosome. ...
Incomplete dominance occurs when certain of the recessive gene appears within the phenotype of the organism, causing a blend in between both the dominant and recessive gene.
Dominant negative Most loss-of-function mutations are recessive. However, some are dominant and are called "dominant negative" mutations. Typically, a dominant negative mutation results in a protein that is structurally similar to the wild-type protein, but which has lost the normal function. Such proteins may be competitive inhibitors of the normal protein function. In genetics, the term recessive gene refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele). ...
In biochemistry there are three ways in which certain chemical substances may reduce or prevent the activities of enzymes: competitive, non-competitive and uncompetitive inhibition. ...
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