Allele vs Gene

Comparison chart

   Allele : Refers to a specific variation of a gene.   

  Gene:  A section of DNA that controls a certain trait.

Function

A gene is a stretch of DNA that codes for a polypeptide via an RNA chain. These coded chains lead to “traits” in an individual, such as eye color and blood type. A gene is the basic unit of heredity.

An allele is a variation of a gene. Genes come in many different forms, or alleles, that lead to the encoding of different RNA chains and, therefore, different traits.

Blood Group

Another example is blood types in humans. At the gene locus three alleles—IA, IB, and IO—determine compatibility of blood transfusions. An individual has one of the six possible genotypes (AA, AO, BB, BO, AB, and OO) that produce one of four possible phenotypes: "A" (produced by AA homozygous and AO heterozygous genotypes), "B" (produced by BB homozygous and BO heterozygous genotypes), "AB" heterozygotes, and "O" homozygotes.

It is now known that each of the A, B, and O alleles is actually a class of multiple alleles with different DNA sequences that produce proteins with identical properties: more than 70 alleles are known at the ABO locus. An individual with "Type A" blood may be an AO heterozygote, an AA homozygote, or an A'A heterozygote with two different 'A' alleles.

Wild and Mutant Alleles

"Wild" alleles are used to describe phenotypic characters seen in 'wild' population of subjects like fruit flies. While wild alleles are considered dominant and normal, "mutant" alleles are recessive and harmful. Wild alleles are believed to be homozygous at most gene loci. Mutant alleles are homozygous in a small fraction of gene loci and are considered infected with a genetic disease and more frequently in heterozygous form in "carriers" for the mutant allele. Mostly all gene loci are polymorphic with multiple variations of alleles in which the genetic variations mostly produce the obvious phenotypic traits.