heterozygote

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heterozygote

biology

Also known as: heterozygous allele

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June 29, 2026

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A heterozygote is an organism that has two different genes, or alleles, for a specific trait. This is in contrast to a homozygote, which has identical pairs of genes for a trait.1

When an organism is heterozygous for a trait, the genes for that trait are different. For example, if one allele (R₁) codes for red flowers and another (R₂) codes for white flowers, a heterozygote (R₁R₂) might display an intermediate trait, such as pink flowers. This phenomenon is known as incomplete dominance. In other cases, like the human MN blood group system, both alleles in a heterozygote can be expressed, resulting in the presence of both antigens (codominance).2

The concept of heterozygosity is fundamental to understanding genetics and how traits are inherited.3

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human genetic disease
Autosomal dominant inheritance
It manifests itself in the heterozygote (designated Aa), who receives a mutant gene (designated a) from one parent and a normal (“wild-type”) gene (designated A) from the other. In such a case the pedigree (i.e., a pictorial representation of family history) is vertical—that is, the disease passes from one generation…
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It manifests itself in the heterozygote (designated Aa), who receives a mutant gene (designated a) from one parent and a normal (“wild-type”) gene (designated A) from the other. In such a case the pedigree (i.e., a pictorial representation of family history) is vertical—that is, the disease passes from one generation…
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allele
…different, the organism’s genotype is heterozygous. A dominant allele will override the traits of a recessive allele in a heterozygous pairing. In some traits, however, alleles may be codominant—i.e., neither acts as dominant or recessive. An example is the human ABO blood group system; persons with
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…different, the organism’s genotype is heterozygous. A dominant allele will override the traits of a recessive allele in a heterozygous pairing. In some traits, however, alleles may be codominant—i.e., neither acts as dominant or recessive. An example is the human ABO blood group system; persons with
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homozygote
In a heterozygous organism, or heterozygote, the genes for a specific trait are different.
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In a heterozygous organism, or heterozygote, the genes for a specific trait are different.
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consanguinity
Homozygosity and heterozygosity
In genetics an allele that is carried at the same position in both of a pair of chromosomes is called homozygous. An allele may be rare in the general population, but, if the parent possesses it, it is transmitted from parent to child with…
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In genetics an allele that is carried at the same position in both of a pair of chromosomes is called homozygous. An allele may be rare in the general population, but, if the parent possesses it, it is transmitted from parent to child with…
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