An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous. Though the term allele was originally used to describe variation among genes, it now also refers to variation among non-coding DNA sequences.
To play the media you will need to either update your browser to a recent version or update your Flash plugin
"Allele" is the word that we use to describe the alternative form or versions of a gene. People inherit one allele for each autosomal gene from each parent, and we tend to lump the alleles into categories. Typically, we call them either normal or wild-type alleles, or abnormal, or mutant alleles.
Leslie G. Biesecker, M.D.
Chief and Senior Investigator, Genetic Disease Research Branch; Head, Human Development Section and Physician Scientist Development Program
Dr. Biesecker's research focuses on the clinical and molecular delineation of human malformation syndromes. Currently, his laboratory is working on two classes of disorders, classic multiple congenital anomaly syndromes and segmental overgrowth disorders. The goals of his research program are to improve the medical care of patients affected by these disorders, provide generalized knowledge about the broad field of birth defects, and better understand basic mechanisms of normal and abnormal human development. Dr. Biesecker's group studies several multiple congenital anomaly syndromes, including Pallister-Hall syndrome, McKusick-Kaufman syndrome, Bardet-Biedl syndrome and Lenz microphthalmia syndrome.