De novo mutation

A genetic change that first arises in an individual rather than being inherited from a parent. It may occur in a parental egg or sperm, after fertilization, or in both.

Germline mutation: A genetic change in an egg, sperm, or their precursor cells that can be passed to offspring. A mutation in a parental germ cell can be present in a child without appearing in either parent's body cells.
Rare disease: A disease affecting a small proportion of a population, often defined by a jurisdiction-specific prevalence threshold. De novo variants account for some rare disorders, especially when a condition is severe and dominant.
Inherited mutation: A genetic change passed from a parent to offspring through an egg or sperm. Unlike a de novo mutation, an inherited mutation is already present in a parent's transmitted genetic material.
Variant of uncertain significance: A genetic variant for which available evidence is insufficient to determine whether it causes disease. A variant can be confidently identified as new while its clinical significance remains uncertain.
Mosaicism: The presence of genetically distinct cell populations within one individual, descended from a single fertilized egg. A mutation arising after fertilization may affect only some of the individual's cells.
Autosomal dominant inheritance: An inheritance pattern in which one altered copy of a gene can cause a trait or disorder. A dominant disorder can appear in a child through a new variant despite no affected parent.
Somatic mutation: A genetic change arising in a non-reproductive cell that is passed to descendant cells but usually not offspring. A somatic mutation may be new within a person but differs from a germline mutation transmissible to children.
Penetrance: The proportion of people with a particular genotype who show the associated trait or disorder. A new disease-associated variant may not produce symptoms because penetrance can be incomplete.
Mutation rate: The frequency at which new genetic changes arise over a specified amount of biological replication or time. Mutation rates help estimate how often new variants arise in gametes and embryos.
Genetic counseling: A process that helps people understand genetic conditions, testing, inheritance, and reproductive choices. Counseling uses the variant's likely origin to discuss recurrence risk for future pregnancies.

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