What Is an Allele?
An allele is one of two or more versions of a gene that exist at the same location on a chromosome. Since a person inherits one copy of each gene from each parent, they typically have two alleles for every gene, one maternal and one paternal.
Alleles can be identical (homozygous) or different (heterozygous). Differences between alleles account for much of human genetic variation, including physical traits and, in some cases, disease risk. For example, different alleles of a single gene can determine blood type or influence the likelihood of developing certain hereditary conditions.
Related Definitions
- What Is a Gene?: the segment of DNA that alleles are versions of.
- What Is Genotype vs. Phenotype?: how your alleles relate to the traits you can see.
- What Is a Variant?: a difference in DNA compared with a reference.
- What Is a SNP (Single Nucleotide Polymorphism)?: a common single letter difference in DNA.
See Which Alleles You Carry
Whole genome sequencing reads 100% of your DNA, including both copies of more than 30,000 genes. Sequencing's Kit Bundles include a Whole Genome Sequencing kit and Next Gen Disease Screening, which analyzes your genome for more than 15,000 conditions. Bring your results to a doctor or genetic counselor to understand what your alleles mean for your health.
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Frequently Asked Questions About Alleles
What is an allele?
An allele is one of two or more versions of a gene that exist at the same location on a chromosome.
How many alleles does a person have for each gene?
A person usually has two alleles for every gene, one from each parent.
What is the difference between homozygous and heterozygous?
Homozygous means the two alleles of a gene are identical. Heterozygous means the two alleles are different.
How do alleles affect traits and health?
Differences between alleles account for much of human genetic variation, including physical traits and, in some cases, disease risk. For example, different alleles of a single gene can determine blood type or influence the likelihood of certain hereditary conditions.
Is an allele the same as a gene?
No. A gene is a segment of DNA that carries instructions. An allele is one version of that gene. People share the same genes but can carry different alleles.
Can DNA testing show which alleles I carry?
Whole genome sequencing reads 100% of your DNA, which includes both copies of each of your genes, so it can show which versions you carry. A doctor or genetic counselor can explain what a result means for your health.
References
This article is for education and is not a substitute for professional medical advice, diagnosis, or treatment. Talk to a qualified healthcare provider about your own health.