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Allele Definition

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An allele is an essential term of genetics. Gene is the structural unit of the chromosome, which carries heredity from one generation to another. The alleles are the pair of genes, which is located in a specific area of the chromosome. On this page, we are going to define allele and discuss what is the meaning of allele.

Allele Definition - There are different variants of genes present in a chromosome. An allele is a variant of the gene, which locates in a chromosome's specific location as a pair of genes. 

In the human chromosome, alleles are present in pairs and maintain the same trait. Therefore, humans are diploid organisms. Two similar alleles are present in each genetic locus, where one allele is inherited from each parent. Also, an allele can be two or more variants of a gene at one genetic locus. But all the alleles maintain the same trait at a genetic locus of the chromosome.

Alleles Meaning In Biology

Now, we will discuss alleles meaning. The word allele comes from the Greek word 'allos'. An allele is the modern formation of that word. The word 'allos' means other. In biology, an allele means different varieties of a gene. The alleles present in a particular genetic locus maintain the same trait. Though alleles are present in a locus as a pair, they can also be found in more than two numbers. In the human chromosome, alleles are present in a pair only to carry the heredity.

Genotype of Allele

Alleles are located in a particular location of the chromosome. The chromosome is the central unit of an organism. All the alleles present in an organism build its genotype. Genotype can be of two types depending on the similarity of the alleles. 

When a pair of alleles are the same, they build homozygous genotypes. When the pair of alleles in a location are not similar, they build heterozygous genotypes. In the case of homozygous genotype, the allele is not dominant or recessive. But the heterozygous genotype includes one dominant allele. The dominant allele overrules the features of the recessive allele.

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Example of Allele

Now, we will be discussing some examples of alleles. Here, we are taking the example of a pea plant. The alleles for the colour of the flower build heterozygous genotype, where the purple allele is dominant, and white is recessive. For the height of the plant, tall is the dominant allele, and short is recessive. For the pea colour, the dominant allele is yellow, and the recessive allele is green. In these three cases, the dominant alleles overrule the recessive alleles' feature in the case of heterozygous genotype. Also, the eye colour and hair colour of human organisms can be observed as the example of alleles.

Difference Between a Gene and an Allele

There are some fundamental differences between gene and allele. The differences between a gene and allele are given below in a tabular form.

Subject

Gene

Allele

Definition

It is a hereditary information unit made up of DNA and consists of genetic information to transmit characteristics.

An allele is a variation of the gene. 

Genetic Locus

They are located at a specific genetic locus, consisting of two copies, each of the parents.

The two copies at the specific genetic locus are called alleles.

Interrelation

A gene may contain different alleles.

An allele is present inside the gene upon which the character of a person is dependent.

Solved Examples

1. Give an Example of an Allele.

Solution: The genetic locus of each gene that consists of two alleles for different characteristics can be seen in the pea plant. In an experiment, it was seen that, for colour, the plants are purple due to the dominant allele and white due to the recessive allele. In height, they are tall due to the dominant allele and short due to the recessive allele. Like these, the other traits are governed by the dominant alleles in the specific genetic locus. 

Conclusion

Biology is a vital subject of the Class 10 curriculum. The students should read all the chapters of biology sincerely. In Class 10, the biology syllabus contains introductory chapters of some important conceptual topics. The students should read all the chapters for their future convenience. These chapters will help them in higher studies. Genetics is a vital part of biology. The students can easily learn the primary concept of genetics in Class 10 from this page. 

FAQ (Frequently Asked Questions)

Q1. What is Allele in Biology?

Ans: The different forms of the same gene is known as an allele. The physical appearance of the phenotype of an organism is affected by the alleles. The genes with various forms are located in the same position or on the genetic locus in the chromosome. Humans have one allele inherited from each parent: having two alleles on each genetic locus, thus making them diploid organisms. Depending on the type of the two alleles, they are categorized as homozygous and heterozygous, which is also known as the gene's genotype. If the two alleles are the same, then it is homozygous, and if the alleles differ, then it is heterozygous. Out of the two alleles, one is dominant, and one is recessive. An organism with a specific heterozygous locus that carries two different types of alleles will show the dominant one's characteristic.

Q2. What are Multiple Alleles?

Ans: When many variations of a gene are present in a population, multiple alleles exist. Though human organisms are diploid, some alleles are present in the human chromosome with more than two variations. Multiple alleles are the result of spontaneous mutation. 

For example, the human eye colour and blood group system are examples of multiple alleles. More than two variations of human eye colour are caused by the pigmentation of the iris and the frequency of light scattering. Different variants of the human blood group are caused by red blood cell type, plasma and antigens of the red blood cell.