An allelle is the alternative form of genes that contribute to human genetic variation.
Explanation:
Any change in the DNA sequencing which leads to the difference between individuals is called genetic variation.
A trait is the characteristic feature which is passed on from one generation to another.
Different forms of traits expressed by different individuals are characterized by genes present in the DNA. The variant or alternative form of genes which leads to such genetic variation is called an allele. This produces the characteristic differences among humans.
Alleles are found in pairs and can either be recessive or dominant depending upon the genotypes (heterozygous or homozygous).
Characteristics like color of the eye or hair, the height of an individual, length or shape of the nose, and various other specific characteristics are expressed by these alleles
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