What does disomic mean?
Disomic is a technical adjective from genetics meaning "having two." Specifically, it describes a cell, organism, or breeding line in which there are exactly two homologous copies of a given chromosome — the normal, balanced condition for that chromosome within an otherwise variable landscape. The term earns its keep in polyploid plants such as wheat, where many chromosomes are present but still behave as orderly pairs, so geneticists speak of "disomic inheritance" to signal that alleles segregate as if the plant were a simple diploid. Its opposite numbers — monosomic (one copy), trisomic (three), and the broader term aneuploid (an abnormal total) — give it a precise place in a family of counting words. Though essentially unknown outside cytogenetics and plant-breeding literature, disomic illustrates how scientific English builds exactness from Greek roots, and it is indispensable wherever researchers must state unambiguously that a chromosome count is normal rather than deficient or excessive.
adjectiveHaving or relating to two copies of each chromosome in a cell; used chiefly in genetics to describe cells or organisms with the normal diploid number for a particular chromosome.
- (Genetics) Describing a cell, line, or organism that possesses exactly two homologous copies of a given chromosome, i.e. the normal condition for that chromosome.
- (Genetics) Describing inheritance in which alleles segregate according to normal pairing of homologous chromosomes, as opposed to polysomic inheritance.
"In wheat genetics, disomic inheritance indicates that each gene is carried on a pair of homologous chromosomes."
"The disomic addition line carried a single pair of chromosomes from the wild relative."
"Because the species is allopolyploid, its genes show disomic rather than tetrasomic segregation."
Bread wheat survives as a hexaploid only because its chromosomes pair up neatly in threes of disomic pairs — lose that orderliness and it becomes sterile.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of disomic
Disomic derives from the Greek prefix di- (or dis-), meaning "twice," combined with soma, meaning "body" — the same root that gives us chromosome, literally "colored body." The word was coined in the early twentieth century alongside related terms such as monosomic and trisomic as cytogeneticists learned to count and classify chromosome complements under the microscope. It shares its -some element with somatic and chromosome, all pointing back to the Greek notion of a bodily structure.
How disomic is actually used
Strictly technical vocabulary confined to cytogenetics, plant breeding, and medical genetics; rarely encountered outside the scientific literature. It carries no figurative or colloquial use and no evaluative connotation.
Easily confused with disomic
"Diploid" describes a whole organism or cell carrying two complete sets of chromosomes, while "disomic" more narrowly describes the presence of exactly two copies of a specific chromosome or chromosomal segment.