germline mosaicism

Full Definition

Germline mosaicism occurs when an individual has two or more genetically different cell populations within their germ cells (eggs or sperm), while their somatic cells remain genetically uniform. This phenomenon can result in multiple affected offspring from apparently unaffected parents, significantly complicating genetic counseling and risk assessment. Germline mosaicism explains cases where recurrence risks are higher than expected for de novo mutations and can affect inheritance patterns in families.

Usage

Usage note: Always lowercase except when beginning a sentence.

In Context

• "Germline mosaicism was suspected when the second child was born with the same de novo mutation." — Genetic counseling documentation
• "The family history suggested possible germline mosaicism in the unaffected father." — Clinical genetics report