Difference between Incomplete Dominance and Codominance: Understanding genetic inheritance is crucial in many fields such as agriculture, animal breeding, and human genetics. However, the genetics of traits can get complicated as there are different patterns of inheritance beyond simple dominance and recessiveness.
Two important alternative patterns are incomplete dominance and codominance. Both patterns involve heterozygotes that are neither fully dominant nor recessive. With incomplete dominance, the phenotype of the heterozygote is intermediate between the two homozygotes. Codominance, on the other hand, results in the heterozygote exhibiting both phenotypes simultaneously. While these genetic concepts may sound intimidating, both simply refer to situations where two alleles interact in an offspring to create multiple phenotypes rather than just one or the other parental versions. Distinguishing between incomplete dominance, where the phenotype is a blended combination of the two alleles, versus codominance, where both alleles are fully expressed simultaneously in heterozygotes, will help clarify misconceptions and allow you to apply these genetic patterns to real-world examples.Difference Between Incomplete Dominance and Codominance | ||
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Feature | Incomplete Dominance | Codominance |
Definition | Neither allele is completely dominant; results in an intermediate phenotype in heterozygotes. | Both alleles are fully expressed in heterozygotes, leading to the simultaneous presence of both phenotypic traits. |
Phenotypic Expression | Blend of traits in heterozygotes; no dominant or recessive allele. | Simultaneous expression of both alleles; no blending of traits. |
Example in Humans | Wavy hair in offspring of a straight-haired and curly-haired parent. | AB blood type in the ABO blood group system. |
Genetic Inheritance Pattern | No clear dominant or recessive allele; unique phenotypic outcome. | Both alleles are equally dominant, coexisting without dominance. |
Allele Interaction | Alleles interact to produce an intermediate phenotype. | Both alleles independently and fully contribute to the phenotype. |
Genetic Symbolism | Represented by superscript letters (e.g., RW for wavy hair). | Represented by both alleles' symbols (e.g., IAIB for AB blood type). |
Phenotypic Ratio in Offspring | 1:2:1 for homozygous dominant:heterozygous:homozygous recessive. | 1:2:1 for homozygous A:heterozygous AB:homozygous B in blood type. |
Overall Outcome | Phenotypes show a spectrum or range of traits. | Phenotypes display both traits simultaneously without blending. |
Genetic Diversity | Contributes to genetic diversity through intermediate phenotypes. | Enhances genetic diversity by maintaining distinct phenotypic traits. |
Common Examples | Flower color in snapdragons; coat color in some animals. | ABO blood group system; coat color in certain animals. |
Organisms Affected | Observed in plants, animals, and humans. | Observed in various organisms, including humans and animals. |