Difference Between Incomplete Dominance and Codominance
Difference between Incomplete Dominance and Codominance: Incomplete dominance and codominance are both non-Mendelian inheritance patterns involving the expression of alleles.
Krati Saraswat24 Jan, 2024
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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 Overview
Codominance and incomplete dominance represent two distinct patterns of genetic inheritance. Codominance occurs when neither allele in a heterozygous individual completely masks the expression of the other allele. In contrast, incomplete dominance is characterized by a dominant allele that does not entirely suppress the effects of a recessive allele. Incomplete dominance contributes to genetic diversity by generating intermediate phenotypes, and its occurrence is not limited to specific organisms, encompassing plants, animals, and humans. The blending of traits provides a spectrum of phenotypic outcomes, fostering variability within populations. To delve deeper into these terms, continue reading below.
Difference Between Incomplete Dominance and Codominance in Tabular Form
Understanding the difference between incomplete dominance and codominance is crucial for students studying genetics. These concepts not only play a vital role in genetic inheritance, but also have real-world applications in medicine and agriculture. Below table shows the difference between incomplete dominance and codominance:| Difference Between Incomplete Dominance and Codominance | ||
|---|---|---|
| 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. |
What is Incomplete Dominance?
Incomplete dominance occurs when two true-breeding parents are crossed, resulting in intermediate offspring. Also known as partial dominance or intermediate inheritance, this phenomenon involves alleles that are not expressed as strictly dominant or recessive. In incomplete dominance, the dominant allele is expressed in a reduced ratio, and the resulting phenotype is a blend of both alleles. Incomplete dominance can also be termed semi-dominance and partial dominance, reflecting the shared expression of both alleles without complete dominance of one over the other. This lack of complete dominance leads to a phenotype that is a combination of the parental traits, generating a third phenotype. Homozygous organisms possess two identical alleles for a specific gene, while heterozygous organisms have two different alleles. The dominant allele masks or suppresses other alleles, while the recessive allele is suppressed and does not manifest in the offspring. Multiple alleles refer to two or more alleles for the same gene. In terms of gene interaction, incomplete dominance results in an intermediate or different phenotype. For example, in roses, the allele for red color is dominant over the allele for white color, but heterozygous flowers exhibit a pink color. The mechanism of incomplete dominance occurs because neither allele is completely dominant, leading to a phenotype that combines both traits. Gregor Mendel's experiments on pea plants initially established the laws of inheritance, but subsequent research on other plants revealed variations, particularly in the F1 generation, where traits appeared intermediate. The Snapdragon flower serves as an example of incomplete dominance in a monohybrid cross. The F1 generation produced pink flowers from the cross of true-breeding red and white flowers, and self-pollination resulted in an F2 generation with a ratio of red, pink, and white flowers. Examples of incomplete dominance extend to humans, where traits like hair texture can exhibit intermediate forms when individuals with different alleles mate. Animals, including chickens, cats, rabbits, dogs, and horses, also display incomplete dominance in traits such as coat patterns and spots. In plants, the Carnation flower exemplifies incomplete dominance, with a cross between white and red flowers producing pink offspring. Overall, incomplete dominance highlights the nuanced interactions between alleles, resulting in phenotypes that reflect a combination of parental traits.What is Codominance?
Codominance is a phenomenon where both alleles or traits of genotypes are expressed simultaneously in the offspring. Unlike in cross-breeding with dominant and recessive alleles, codominance lacks a hierarchy between the alleles. Instead, both alleles persist, forming a blend of their characteristics that contributes to the phenotypic expression during breeding. Codominance is often characterized by the simultaneous presence and expression of both alleles in the offspring, leading to a phenotype that differs from the genotypes of homozygotes. The resulting phenotype is distinct from that of homozygotes, and codominance is frequently observed in both animals and plants, particularly in instances involving color differentiation. In humans, a notable example of codominance is evident in blood types. Codominance entails a combination of allelic expressions, showcasing the coexistence of both alleles in the offspring. It is essential to note that, in both incomplete dominance and codominance, the parent alleles persist in the heterozygote, and neither allele exerts dominance over the other. This absence of dominance allows for the unique expression of both alleles in the progeny. Keep exploring the fascinating world of genetics and science by enrolling yourself in NEET online coaching by Physics Wallah . With personalized coaching from expert educators and access to interactive study material, this online platform provides the best learning experience for students preparing for competitive exams like NEET. Don't let doubts or confusion hold you back from achieving your academic goals.Difference Between Incomplete Dominance and Codominance FAQs
What is Incomplete Dominance?
Incomplete dominance is a genetic inheritance pattern where neither of two alleles is dominant, resulting in an intermediate or blended phenotype in heterozygous individuals.
What is Codominance?
Codominance is a genetic inheritance pattern where both alleles in a heterozygous individual are fully expressed, leading to the simultaneous presence of both phenotypic traits without blending.
How does Incomplete Dominance differ from Complete Dominance?
In complete dominance, one allele is entirely dominant over the other, resulting in a clear dominant and recessive phenotype. In incomplete dominance, there's a blending of phenotypes in heterozygous individuals.
Can you provide an example of Incomplete Dominance in humans?
An example of incomplete dominance in humans is the expression of wavy hair when a straight-haired individual mates with a curly-haired individual, resulting in wavy-haired offspring.
What is an example of Codominance in blood type?
The ABO blood group system is an example of codominance. The presence of both A and B alleles results in the AB blood type, where both antigens are expressed simultaneously.
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