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Codominant

Biology  Codominance  Codon

codominant
the expression of both of two different alleles in a heterozygote
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ...


Codominant alleles
Codominant alleles occur when rather than expressing an intermediate phenotype, the heterozygotes express both homozygous phenotypes. An example is in human ABO blood types, the heterozygote AB type manufactures antibodies to both A and B types.

Codominant alleles: pairs of alleles that both affect the phenotype when present in a heterozygote.
Locus: the particular position on homologous chromosomes of a gene.
Homozygous: having two identical alleles of a gene.

How are codominant alleles represented?
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Codominant alleles any two alleles which are both expressed in the phenotype of a heterozygous organisms.
Codon a triplet of bases in messenger RNA (mRNA) that codes for a particular amino acid during the synthesis of proteins.

D. ~, complimentary
E. dominant, recessive
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An example of a codominant trait occurs in certain types of calves (cow's young). Some calves are known as "blue roans" for their appearance of both blue and grey hairs.

Inherited translocations are passed through generations in a codominant fashion. Since one copy of each chromosome remains normal, both parent and progeny with such a translocation are heterozygous , or "balanced" carriers.

Thus, the heterozygote (A1/A2) and both homozygotes (A1/A1 and A2/A2) are all distinguishable from each other and A1 and A2 would be considered to be "codominant".

An isoenzyme whose synthesis is controlled by codominant alleles of one gene.
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A and B are codominant. Both alleles make antigens when present in the same individual. A and B are both dominant to O. If a person's phenotype is type AB, you know their genotype is AB. If a person is type O, you know their genotype is OO. But if a person is type A, they can be AA or AO.

An isoenzyme whose synthesis is controlled by codominant alleles of one gene.
Related Terms:
Isoenzyme (isozyme)
Multiple forms of an enzyme whose synthesis is controlled by more than one gene. See also alloenzyme.

At the molecular level, the two alleles are codominant as both normal and abnormal (sickle-cell) hemoglobins are synthesized.
About one in ten African-Americans has sickle-cell trait.

The alleles are black and orange but they are codominant.
Example.
XBXB = black female ...

See also: See also: What is the meaning of Dominant, Alleles, Phenotype, Allele, Homozygous?

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