Difference Between Allele and Genotype

The key difference between allele and genotype is that the allele is one of the variant forms of a gene located at the same genetic locus of a chromosome while genotype is the genetic constitution of a particular trait.

Genetics is the study of genes and hereditary patterns in organisms. Chromosomes are the structures that contain the genetic information of an organism. Therefore, in eukaryotes, there is a specific number of chromosomes present in the genome. Each chromosome has thousands of genes that are specific regions of the chromosomes. In fact, genes are structural units in genetics that store genetic information to produce proteins. Each gene has two copies descending from each parent.

Similarly, an allele is a variant of a gene or form of a gene. Moreover, each gene has two forms of alleles that determine the characteristic encoded by the gene. Hence, genotype is the genetic makeup of an organism which is determined by the distribution of alleles in different genes.

CONTENTS

1. Overview and Key Difference
2. What is an Allele
3. What is a Genotype
4. Similarities Between Allele and Genotype
5. Side by Side Comparison – Allele vs Genotype in Tabular Form
6. Summary

What is an Allele?

An allele is a variant form of a gene. Each has two forms of the gene inherited from its father and mother. The allele distribution varies from organisms to organism eventhough it is situated in the same gene locus on a chromosome. Some organisms inherit the same allele of the gene from both parents, whereas some inherit the two different forms of alleles. Likewise, each gene has its own alleles. These alleles determine the characteristic of the gene. Therefore, each characteristic such as hair colour, skin tone, physiological processes, etc, is a result of the allelic distributions in an organism.

Alleles can be either dominant or recessive. When the dominant alleles are present, they express the dominant phenotype masking the recessive allele phenotype. In addition, depending on the presence of the dominant and recessive alleles, genes are further classified as homozygous and heterozygous. The homozygous condition occurs when two similar alleles are present in the two chromosomes; either two dominant alleles ortwo recessive alleles. In contrast, the heterozygous condition is when, alternative forms of the two alleles are present in a particular gene, where one allele is dominant, and the other is recessive.

What is a Genotype?

Genotype is the genetic makeup of an organism. It refers to the complete set of genes in an organism. Therefore, the genotype of an organism varies based on the allelic distribution of an individual organism. Thus, the product of each pair of allele in a gene represents the genotype of that particular gene. Therefore, in a single locus of a chromosome, three types of genotypes can be observed. This is based on the alleles of the particular gene.

The three types of genotypes are;

• Homozygous dominant, where both the alleles are of the same form and are dominant (AA).
• Homozygous recessive, where both the alleles are of the same form and are recessive (aa).
• Heterozygous, both alleles are of different forms (Aa).

The expression of the genotype is known as the phenotype. Therefore, the observed characters are phenotypes of the respective genotypes determined by the allele distribution.

What are the Similarities Between Allele and Genotype?

• Allele and genotype are important definitions in Genetics.
• Both were first introduced by Mendel’s experiments.
• Furthermore, these two concepts are dependent on each other
• Also, both deal in terms of DNA and chromosomes.

What is the Difference Between Allele and Genotype?

Allele is one of some alternative forms of the same gene that is responsible for determining contrasting characteristics. On the other hand, genotype is the total genetic constituent of an organism which results in the external appearance of a particular trait. Therefore, this is the key difference between allele and genotype. Also, allele can be either dominant allele or recessive allele while the genotype can be homozygous dominant, homozygous recessive or heterozygous. Therefore, it is also a difference between allele and genotype.

Summary – Allele vs Genotype

Allele and genotype are two important concepts in Genetics. Allele is a variant form of a gene. Gene has two alleles that inherited from each parent. Alleles situate in the same genetic locus of the chromosome. On the other hand, genotype is the genetic composition of a particular trait or an organism. Genotype varies according to the distribution of the alleles in a gene. This summarizes the difference between allele and genotype.

Reference:

1. “Allele.” Nature News, Nature Publishing Group. Available here  
2. “Genotype.” Nature News, Nature Publishing Group. Available here  

Image Courtesy:

1.”Gene Loci and Alleles”By Keith Chan – Own work, (CC BY-SA 4.0) via Commons Wikimedia  
2.”SimpleGenotypePhenotypeMap”By Alphillips6 – Own work, (CC BY-SA 4.0) via Commons Wikimedia