Demystifying Allele Definition: What You Need to Know

Demystifying Allele Definition: What You Need to Know


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  • Source: Microbioz India

  • Date: 12 Mar,2024

In addition to knowing about genetics, you must also know about alleles. Below is a brief on all you need to know about alleles.

What are Alleles?

Alleles are different forms of the same gene that are situated at the same place in the chromosome. Every person gets two alleles for each gene, one from each parent.

Types of Alleles:

  1. Dominant Allele: The expression of this allele is its phenotype when it is carried by one individual and hides that of recessive allele; for example Aa form. Capital letters are often used to indicate dominant alleles (e.g., A).
  2. Recessive Allele: You can only see traits arising from this allele if an individual carries two copies of it. Dominant allele hide recessive ones in genotyopes. They are usually marked by small letters (e.g., a).
  3. Co-dominant Alleles: In heterozygous individuals, both alleles appear completely expressed in the phenotype and neither allele dominates over another thus both represent an average resulting into co-dominance as seen in blood type genetics such as AB;
  4. Incomplete Dominance: When heterozygous express traits averaging between those observed homozygotes; e.g pink flowers obtained after crossing red flower with white flower as shown in snapdragon flower color.

Key Concepts:

  1. Genotype: It refers to a specific combination or arrangement of alleles that make up organism’s genetic composition.
  2. Phenotype: This reflects observable traits due to genotype plus environmental factors acting on an organism.
  3. Homozygous: Having similar versions of one particular gene throughout an individual (AA or aa).
  4. Heterozygous: Those having two dissimilar alleles for any given gene on their chromosomes like Aa

Inheritance Patterns:

  1. Mendelian Inheritance: Described through Gregor Mendel’s proposals including segregation and independent assortment.
  2. Non-Mendelian Inheritance: Traits that do not adhere to mendelian genetics and these include pleiotropy, incomplete dominance, codominance, polygenic inheritance, sex-linked traits.


  1. Genetic Disorders: This will enable identification of genetic disorders and patterns of diseases.
  2. Selective Breeding: By manipulating alleles in plants or animals, breeders can control what qualities are passed on.
  3. Medical Treatments: Personalized medicine and gene therapy research relies on understanding alleles well enough


Understanding genetics and inheritance is all about alleles. Dominant genes Recessive genes How they are inherited These three things are more complicated than they appear at first when looking at the variety of characteristics that organisms have.


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