Codominance n., <ˈkoʊˈdɑːmɪnəns> Definition: alleles that a gene pair in a heterozygote are fully expressed

Codominance Definition

Codominance is a form of inheritance wherein the alleles the a gene pair in a heterozygote are fully expressed. As a result, the phenotype of the offspring is a mix of the phenotype that the parents. Thus, the characteristics is neither leading nor recessive. Codominance in people is exemplified by people with form AB blood. A human inheriting the alleles IA and IB will have actually a type AB blood since IA and also IB are codominant and therefore will certainly be to express together. Other codominance instances are the white-spotted red flower in plants and the black-and-white-coated mammals.

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Etymology: the term codominance is the mix of co- method “together” and dominance. Variant: co-dominance.

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Alleles and Genes

An allele is a different of a gene. Alleles come in pairs. Each pair has own clues (locus) in the chromosome and controls the exact same trait. The allele that is expressed is described as dominant vice versa, the allele that is masking is explained as recessive.

Alleles and gene

In stimulate to understand codominance, an introduction of the basic concepts is essential. A gene is the fundamental, physical, and functional unit of heredity. It is made up of nucleotides responsible for the physical and heritable characteristics of an organism. It mentions the structure of a certain protein or of an RNA molecule.

A different of a gene is described as an allele. Alleles come in pairs. The pair that alleles rectal a comparable locus (I.e. A point out in the chromosome) and they regulate the same trait. The allele that is express or masks the impact of the other allele is explained as dominant. Vice versa, the allele whose effects are not manifested or are masked through the leading allele is defined as recessive.

Punnett Square

In bespeak to recognize if a characteristics is codominant, a tool called Punnett square may help. Punnett square helps to show all feasible allelic combine in a check cross. It determines the possible genotypes that the offspring. That is a diagram in grids and also letters to represent alleles. An uppercase letter (e.g. A) denotes a leading trait or genotype and also a lowercase denotes a recessive properties or genotype (e.g. a).

Read: Punnett Square – an interpretation and examples

Homozygosity and also Heterozygosity

The genotype is a major factor that determines the phenotype (physical or biochemical characteristics) of one organism. In the given example above, there might be three feasible genotypes: AA, Aa, and also aa. And based on the nature of these alleles, the condition may be homozygous or heterozygous. Homozygosity is the condition wherein the alleles on the locus room the same or similar (e.g. AA or aa). In contrast, heterozygosity is the problem wherein the alleles occupying the very same locus are various (e.g. Aa). AA genotype is homozygous dominant conversely, Aa, heterozygous dominant. The aa genotype is an example of homozygous recessive.


In a general sense, dominance pertains to the state of being “dominant” or “supreme”. In genetics, dominance pertains to a gene or allele expressed end the other genes or alleles. There are three major forms: complete dominance, incomplete dominance, and also codominance.

A codominance Punnett square reflecting a test cross in between a white-furred bull (WW) and also a red-furred cow (RR). All your offspring are heterozygotes (genotype RW), displaying both white and red fur. Codominance is an example of Non-Mendelian inheritance.

When an individual inherited two dominant alleles (e.g. AA) or inherits at least one leading allele (e.g. Aa), that individual will display the trait since of the presence of the dominant allele. In contrast, the individual doing not have the dominant allele (e.g. aa) method that the other trait will manifest because there is no dominant allele come mask it. This is what occurs in the complete dominance and also the resulting sample conforms to the Mendelian inheritance. (1, 2) The dominant allele will certainly be expressed when the recessive allele will certainly be suppressed. Hence, the heterozygous organism (Aa) will have a trait similar to the homozygous dominant (AA). Conversely, those that execute not conform exemplify the non-Mendelian type of inheritance.

Non-Mendelian Inheritance

In non-Mendelian inheritance, the result phenotype the the offspring is different from the phenotypes of either parent. Codominance and incomplete supremacy are examples. (2) In codominance, the alleles that a gene pair in a heterozygote are totally expressed. This results in offspring through a phenotype the is neither dominant nor recessive.

As because that the incomplete dominance definition, this type of inheritance occurs when the phenotype is intermediary to the phenotype that the parents. (2) The dominant allele is just partially expressed and also the resulting heterozygous offspring will display a phenotype that is intermediary to the phenotype that the parents. An instance of incomplete dominance is as soon as a male white flower parental is crossed with a woman red flower the offspring will certainly be a plant that will soon bear pink flowers.

Codominance is different from incomplete prominence in the method that the previous has both alleles manifesting the phenotypes whereas the last produces an intermediate phenotype.

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Below are several of the instances of codominance.

Type ab blood

In the ABO blood type system in humans, blood type AB is an example of codominance. It implies that both leading alleles are present and also expressed together. A genotype of IAIB would an outcome in H antigens with both N-acetylgalactosamine and also galactose.

Type ab blood of the ABO blood kind system is an example of codominance in humans. (3) The red blood cells have antigens on their surface. Among these antigens is the H antigen that is managed by 3 alleles: IA, IB, and also i. Both IA and also IB are dominant alleles that once expressed produce enzymes that modify the H antigen. IA an especially adds N-acetylgalactosamine’’ conversely, IB add to galactose to the H antigen. (4, 5) with ii alleles, thus lacking the dominant alleles, there would certainly be no such adjustments on the H antigen top top the red blood cells. A genotype of IAIA or IAi would result in H antigens through N-acetylgalactosamine top top the red blood cells – a characteristics indicating type A blood. A genotype of IBIB or IBi would an outcome in H antigens with galactose – a characteristics indicating kind B blood. A genotype the IAIB would result in H antigens with both N-acetylgalactosamine and galactose. This indicates form AB blood. Vice versa, a genotype that ii way lacking such modifications on the H antigen and also an clues of a form O blood. In codominance, blood form AB implies that both leading alleles space present and also expressed together.

Black and also white coat

In other animals, codominance is exemplified by a mix the coat color in a progeny of parents with various coat colors. For example, a cross in between a black-furred masculine dog and also a white-furred woman dog might produce offspring through a black-and-white coat. This method that the shade coat properties of the parents are codominant together both were expressed together in the progeny.

White-spotted red flower

Codominance is exemplified by a plant that bears flowers v two distinct shade phenotypes. For instance, a white-spotted red flower can be led to by a cross in between a red flower and a white flower. The alleles for the red and also white color phenotypes average that they are codominant.

Codominance vs Polygenic Inheritance

Take note that codominance is a different concept from polygenic inheritance. If both the them perform not conform to the Mendelian inheritance, they different in the means that in polygenic inheritance multiple genes are connected to produce cumulative effects. (6) In codominance, different alleles that a single gene affect the result trait. Instances of polygenic characteristics in humans are height, weight, skin color, and eye color.

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READ:Dominance – Tutorials

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Discover an ext types of non-Mendelian inheritance such together incomplete dominance and also codominance in this vid.

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