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Genetics: glossary of terms

Benjamin A Raby, MD, MPH
Robert D Blank, MD, PhD
Section Editor
Anne Slavotinek, MBBS, PhD
Deputy Editor
Jennifer S Tirnauer, MD


One of the greatest obstacles clinicians experience in reading about and understanding genetics is the extensive use of technical language and jargon. It should be noted that genetic terms are frequently used imprecisely in published clinical literature. The following is a compilation of some of the most important technical terms.

A more extensive discussion of terms can be accessed in standard genetics reference texts [1]. In addition, a guide for the conventions regarding the proper names of genes and alleles in humans can be found at www.genenames.org/guidelines.html.

Glossaries of epidemiological terms and terms that apply to systematic reviews and meta-analyses are presented separately in UpToDate. (See "Glossary of common biostatistical and epidemiological terms" and "Systematic review and meta-analysis", section on 'Glossary of terms'.)


Allele — An allele is one of a series of alternative forms (genotypes) at locus, or a specific region of a chromosome. At the DNA level, different alleles have different base sequences.

Allele frequency — The proportion of chromosomes in a population harboring a specific allele. "Minor allele frequency" typically refers to the less common variant at a biallelic locus and is usually used to refer to the frequency of a single nucleotide polymorphism (SNP).


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Literature review current through: Jan 2017. | This topic last updated: Mon Jan 23 00:00:00 GMT+00:00 2017.
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