Dominant vs Recessive Allele: Difference and Comparison

Living organisms have a unique trait called genes responsible for the heredity transmission of traits between parents and offspring. A genre can be Dominant and recessive alleles are two contrasting forms of a gene that occupy the same locus or position on a chromosome. In genetics, dominance refers to the relationship between two alleles of a single gene, where the dominant allele overrides the expression of the recessive allele in heterozygous individuals.

Key Takeaways

1. Dominant alleles express their traits even when paired with a different one; recessive alleles only express their traits when paired with an identical one.
2. Dominant alleles can mask the presence of recessive alleles in an organism’s phenotype; recessive alleles remain hidden unless two copies are present.
3. Inherited traits are determined by the combination of dominant and recessive alleles from each parent, following Mendelian inheritance patterns.

Dominant vs Recessive Allele

The difference between Dominant Allele and a Recessive Allele is that a dominant allele can express itself even if one copy of the gene is present. In contrast, a recessive allele must be present in pairs in ogre to be defined.

Both genes and alleles are responsible for inheritance—an allele in a slightly varied form of a gene. A gene is inherited in pairs, one from each parent.

Alleles sometime cause observable changes in the genetic makeup of an organism. Such changes are called Phenotypic changes.

Genetic expression is dependent on such alleles. They may be more than two alleles for a given gene.

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Comparison Table

Feature	Dominant Allele	Recessive Allele
Expression	Always expressed in the phenotype (outward appearance) when present, either alone (homozygous) or paired with a recessive allele (heterozygous).	Only expressed in the phenotype when paired with another recessive allele (homozygous). Masked by a dominant allele in a heterozygous pairing.
Effect on Trait	Determines the trait that is exhibited in the organism.	Does not influence the trait’s outward appearance when paired with a dominant allele.
Notation	Represented by a capital letter (e.g., A, B, T).	Represented by a lowercase letter (e.g., a, b, t).
Example (Pea Plant Seed Color)	Green seed color (dominant trait)	Yellow seed color (recessive trait)
Genotype	AA (homozygous dominant), Aa (heterozygous)	aa (homozygous recessive)
Phenotype	Green seeds (dominant trait is expressed)	Yellow seeds (only expressed in homozygous recessive)

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What is Dominant Allele?

Characteristics of Dominant Alleles:

1. Phenotypic Expression: Dominant alleles determine the observable traits or characteristics of an organism, known as its phenotype. These traits may include physical features, biochemical properties, or physiological functions.
2. Genetic Interaction: Inheritance patterns involving dominant alleles follow specific genetic interactions. When an individual carries one or more dominant alleles for a particular trait, that trait will be expressed in the phenotype, regardless of the presence of recessive alleles.
3. Not Necessarily More Common: Dominant alleles are not inherently more prevalent in populations compared to recessive alleles. Their frequency depends on factors such as natural selection, genetic drift, and mutation rates specific to the gene in question.
4. Denoted by Capital Letters: In genetic notation, dominant alleles are typically represented by capital letters, while recessive alleles are denoted by lowercase letters. For example, in Mendelian genetics, the dominant allele for flower color in pea plants is represented by “P,” while the recessive allele is represented by “p.”

Implications of Dominant Alleles:

1. Mendelian Inheritance: Dominant alleles adhere to Mendel’s principles of segregation and independent assortment during inheritance. They contribute to the diversity of traits observed in offspring through the transmission of genetic information from parents to offspring.
2. Expression in Heterozygotes: Dominant alleles exert their effects in heterozygous individuals, where they mask the expression of recessive alleles. This dominance relationship determines the phenotypic ratio observed in offspring of crosses involving heterozygous parents.
3. Trait Stability: Dominant alleles often confer advantageous traits that contribute to the survival and reproductive success of organisms in their environments. Consequently, these alleles may be maintained in populations over successive generations through natural selection.
4. Medical Genetics: Understanding dominant alleles is crucial in medical genetics for diagnosing genetic disorders and predicting inheritance patterns. Dominant genetic disorders result from mutations in dominant alleles, leading to the expression of disease traits in individuals carrying the mutated allele, even if it is heterozygous.

 

What is Recessive Allele?

Characteristics of Recessive Alleles:

1. Expression in Homozygotes: Recessive alleles are only expressed in the phenotype when present in the homozygous state. In heterozygous individuals, the presence of a dominant allele typically suppresses the expression of the recessive allele.
2. Phenotypic Masking: Recessive alleles are often “masked” by dominant alleles in heterozygous individuals, resulting in the dominant phenotype being observed. This masking effect is a fundamental aspect of genetic interactions between alleles.
3. Genetic Interaction: Inheritance patterns involving recessive alleles follow specific genetic interactions, particularly in the context of Mendelian genetics. Recessive traits may remain hidden across generations and become apparent only when two carriers of the recessive allele produce offspring homozygous for that allele.
4. Denoted by Lowercase Letters: In genetic notation, recessive alleles are typically represented by lowercase letters. This convention distinguishes them from dominant alleles, which are represented by capital letters. For example, in Mendelian genetics, the recessive allele for flower color in pea plants is represented by “p,” while the dominant allele is represented by “P.”

Implications of Recessive Alleles:

1. Mendelian Inheritance: Recessive alleles adhere to Mendel’s principles of segregation and independent assortment during inheritance. They contribute to the diversity of traits observed in offspring, especially when two heterozygous carriers of a recessive allele produce offspring.
2. Expression in Homozygotes: Recessive alleles manifest their effects prominently in individuals homozygous for the allele. This expression pattern is critical for understanding the inheritance of genetic disorders caused by recessive alleles, as affected individuals typically inherit two copies of the mutated recessive allele.
3. Genetic Disorders: Many genetic disorders are caused by mutations in recessive alleles. These disorders often exhibit a recessive inheritance pattern, where affected individuals inherit two copies of the mutated allele, leading to the expression of the disorder’s phenotype.
4. Population Genetics: Recessive alleles contribute to the genetic diversity within populations. They may persist at low frequencies in populations, particularly if they confer deleterious traits in homozygotes but provide a selective advantage in heterozygotes (known as heterozygote advantage or overdominance). Understanding the distribution and dynamics of recessive alleles is essential for population genetics and evolutionary biology.

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Main Differences Between Dominant and Recessive Allele

1. Expression in Phenotype:
   • Dominant Allele: Expressed in the phenotype when present in either homozygous or heterozygous condition.
   • Recessive Allele: Expressed in the phenotype only when present in the homozygous condition.
2. Masking Effect:
   • Dominant Allele: Masks the expression of the recessive allele in heterozygous individuals.
   • Recessive Allele: Can be masked by the presence of a dominant allele in heterozygous individuals.
3. Genetic Notation:
   • Dominant Allele: Typically represented by capital letters in genetic notation.
   • Recessive Allele: Typically represented by lowercase letters in genetic notation.
4. Expression in Homozygotes:
   • Dominant Allele: Can be expressed in both homozygous and heterozygous conditions.
   • Recessive Allele: Only expressed in the phenotype when present in the homozygous condition.
5. Inheritance Patterns:
   • Dominant Allele: Follows dominant inheritance patterns, influencing the phenotype in both homozygous and heterozygous states.
   • Recessive Allele: Follows recessive inheritance patterns, requiring homozygosity for expression in the phenotype.
6. Frequency in Populations:
   • Dominant Allele: Not necessarily more prevalent in populations compared to recessive alleles.
   • Recessive Allele: May persist at low frequencies in populations, especially if deleterious in the homozygous state but providing advantages in heterozygotes.

References

1. https://abt.ucpress.edu/content/ucpabt/53/2/94.full.pdf
2. https://www.nature.com/articles/ng842z

Last Updated : 07 March, 2024