What is an allele?

What is an allele?

• A. The same version of every gene across individuals.
• B. A region of DNA that codes for a protein.
• C. An observable trait of an organism.
• D. A different version of a gene.

Answer: (D)

An allele is a different version of a gene. Alleles are the variant forms that a gene can take, often arising from slight changes in DNA sequence. In diploid organisms, you typically have two alleles for each gene, one from each parent, and these variants can influence how traits are expressed. This concept is what makes genetic variation possible among individuals. The other descriptions don’t fit: a gene region that codes for a protein describes the gene itself, not its variant form; an observable trait is the phenotype, not the allele; and saying there is the same version of every gene across individuals would ignore the natural variation that alleles represent.

An allele is a different version of a gene. Alleles are the variant forms that a gene can take, often arising from slight changes in DNA sequence. In diploid organisms, you typically have two alleles for each gene, one from each parent, and these variants can influence how traits are expressed.

This concept is what makes genetic variation possible among individuals. The other descriptions don’t fit: a gene region that codes for a protein describes the gene itself, not its variant form; an observable trait is the phenotype, not the allele; and saying there is the same version of every gene across individuals would ignore the natural variation that alleles represent.