Iowa Institute of Human Genetics

  • View Glossary Terms

  • V

    Variable expression (variable expressivity):

    Variation in phenotype or clinical features among individuals who share the same gene alteration. Can occur within families or among families.

    Variant (sequence alteration, or mutation):

    An alteration of the nucleotide sequence from the reference genome. Alterations may be benign (polymorphisms), pathogenic (mutation), or of unknown significance.