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Dominance vs. Codominance: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on January 16, 2024
Dominance is when one allele masks the effect of another in a heterozygote, while codominance involves both alleles being fully expressed.

Key Differences

Dominance occurs in genetics when an allele effectively overshadows the expression of another allele, leading to a specific phenotype. Codominance, on the other hand, is a scenario where both alleles in a heterozygous combination are equally expressed, resulting in a phenotype that shows both traits distinctly.
In dominance, the dominant allele's trait is the only one observed in the organism's phenotype, while the recessive allele's influence is masked. Codominance differs as it allows both alleles to contribute to the phenotype, resulting in a mixed or blended manifestation of both traits.
An example of dominance is brown eyes over blue eyes in humans, where the allele for brown eyes masks the effect of the blue eye allele. In codominance, an example would be the AB blood type in humans, where both A and B alleles are equally expressed.
The concept of dominance is crucial in understanding Mendelian genetics and the inheritance of traits, whereas codominance provides insights into more complex genetic interactions and inheritance patterns.
Dominance simplifies the prediction of offspring traits, codominance offers a more nuanced view of genetics, showcasing the diversity and complexity of genetic expression.

Comparison Chart

Expression in Phenotype

One allele masks the other
Both alleles equally expressed

Example in Humans

Brown eyes over blue eyes
AB blood type

Genetic Inheritance

Follows Mendelian patterns
More complex inheritance

Phenotypic Result

Single trait observed
Blend of both traits


Simplifies trait prediction
Shows genetic diversity

Dominance and Codominance Definitions


Dominance is the genetic mechanism where one allele masks the expression of another.
In flower color, red is often dominant over white.


Codominance is the genetic situation where two different traits are fully displayed.
In some flowers, red and white petals are codominantly expressed.


Dominance pertains to the overshadowing effect one allele has in a gene pair.
In birds, the gene for long feathers is dominant over short feathers.


Codominance is when neither allele in a gene pair masks the other.
In certain fish species, both spotted and striped patterns are codominantly expressed.


Dominance is the prevalence of one allele's trait over another.
In pea plants, the allele for tall stems is dominant over short stems.


Codominance pertains to the equal representation of two genetic traits.
In certain birds, black and white feather colors are codominantly expressed.


Dominance refers to the primary influence one genetic variant has over another.
In cats, the allele for black fur is dominant over the allele for white fur.


Codominance refers to the simultaneous expression of both alleles in a heterozygote.
Human blood type AB exhibits codominance of A and B alleles.


Dominance is the superior manifestation of one trait in heterozygous pairings.
In human hair texture, curly is dominant over straight.


Codominance occurs when two alleles are equally expressed in an organism.
In cattle, red and white fur show codominance, resulting in roan coloring.


The condition or fact of being dominant.


A heterozygous condition in which both alleles at a gene locus are fully expressed in the phenotype.


The state of being dominant; of prime importance; supremacy.


(genetics) A condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other.


Being in a position of power, authority or ascendancy over others.


(physiology) The superior development of or preference for one side of the body or one of a pair of organs; such as being right-handed.


The property of a gene such that it suppresses the expression of its allele.


Predominance; ascendency; authority.


Superior development of one side of the body


The state that exists when one person or group has power over another;
Her apparent dominance of her husband was really her attempt to make him pay attention to her


The power or right to give orders or make decisions;
He has the authority to issue warrants
Deputies are given authorization to make arrests


What is dominance in genetics?

Dominance is when one allele's trait overrides another's in a heterozygote.

How does dominance affect inheritance?

It simplifies predicting traits, as dominant alleles are more likely to be expressed.

What is codominance?

Codominance occurs when both alleles in a heterozygote are fully expressed.

What's a common example of dominance?

Brown eyes being dominant over blue eyes in humans.

Can dominance be partial?

Yes, in incomplete dominance, traits blend rather than one completely masking the other.

Does dominance imply superiority?

No, it's purely about genetic expression, not trait quality.

Can codominance occur in humans?

Yes, the AB blood type is a result of codominance.

Is codominance common?

It's less common than dominance but occurs in many species.

How does codominance differ from dominance?

In codominance, both alleles contribute to the phenotype, unlike dominance where one allele overshadows the other.

How do dominance and codominance affect genetic diversity?

Dominance can mask genetic variation, while codominance can reveal it.

Is codominance predictable like dominance?

It can be predictable, but the patterns are more complex.

Are dominance and codominance mutually exclusive?

Yes, a gene pair can exhibit either dominance or codominance, not both simultaneously.

Can environment affect dominance and codominance?

Yes, environmental factors can influence the expression of genes.

How do dominance and codominance relate to genetic disorders?

Both can play a role in the inheritance and expression of genetic disorders.

What are some examples of codominance in animals?

Roan fur in cattle and certain patterns in flowers.

Does dominance always mean one allele is more common?

No, dominance refers to expression, not frequency.

Can codominance occur in plant traits?

Yes, it's often seen in flower color and leaf patterns.

Can codominance lead to new traits?

Yes, it can result in phenotypes that are a mix of both alleles.

How do dominance and codominance play a role in evolution?

They contribute to genetic variation, which is essential for natural selection.

Is it easier to study dominance or codominance in genetics?

Dominance is generally simpler to study due to more straightforward patterns.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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