clonality

Clonality describes the state of being genetically identical or derived from a single common ancestor. In biology, a clone is an organism or lineage produced by mitotic division or asexual reproduction, so that the descendants share an essentially identical genome at the time of origin, subject to later mutations.

Clonality occurs in many contexts. Plants commonly propagate clonally by runners, bulbs, or cuttings, yielding populations of genetically identical individuals. Some animal species reproduce asexually, forming clonal lineages. Microbial populations can also be clonal when they originate from a single cell, though mutation and selection generate diversity over time. In medicine, cancer routinely exhibits clonal expansion, where a founding neoplastic cell gives rise to a tumor composed of genetically related cells.

Detecting clonality relies on genetic markers and lineage tracing. Microsatellite markers, single-nucleotide polymorphisms, or copy-number data assess genetic identity among samples. Immunology uses rearrangements of immunoglobulin and T-cell receptor genes to distinguish clonal proliferations from reactive processes. In experimental biology, lineage tracing uses heritable labels to follow cell lineages.

Clonality has ecological and evolutionary consequences. Clonal populations can dominate in stable environments but often harbor reduced genetic diversity, potentially limiting adaptation and increasing vulnerability to disease. In oncology, clonal evolution and intratumor heterogeneity influence prognosis and treatment response.