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the branch of cytology that studies the structure and functions both of the cell nucleus as a whole and of its substructures (chromosomes, nucleolus, nuclear membrane), using optical and electron microscopy, cytochemistry, and isotopic indicators (mainly autoradiography).

Karyology developed at the turn of the 20th century after the cell nucleus had been found to play the major part in heredity. The main achievements of the science include the establishment of the microscopic and submicroscopic structure and behavior of the nuclear elements, both during interphase and during the various forms of nuclear division (amitosis, mitosis, meiosis, endomitosis) and the determination of the structure and mechanisms of chromosomal reproduction (reduplication). The science of cytogenetics grew out of the studies of genetics and karyology. In close contact with cytogenetics, developmental biology, and molecular biology, karyology studies the regular mechanisms of the transformations and function of the chromosomes and the individual parts thereof during the development and differentiation of cellular systems. A current concern of karyology is the structure of chromosomes and chromosomal subunits (however, finding a method of constructing elementary chromosomal strands from nucleic acids and proteins is a concern of molecular biology).

The word “karyology” is sometimes taken to mean just one of the science’s traditional fields of study: the investigation of chromosomal sets (karyotypes). Comparisons of the karyotypes of the different cells of an organism and of organisms of a single species have revealed that the karyotype is constant within a given species. The theory of evolution, together with karyosys-tematics (karyotaxonomy), makes use of this principle to establish the degree of kinship between closely related species, to define twin species, and to isolate new species. Human karyology has been developing rapidly since the 1950’s and helping to reveal the chromosomal nature of a number of hereditary diseases and developmental anomalies in man. The international journal Caryologia (issued by the University of Florence since 1948) publishes articles on karyology, cytology, cytosystematics, and cytogenetics. In the USSR and abroad the findings of karyology are also published in many journals of cytology and genetics.


Rukovodstvo po tsitologii, vols. 1–2. Moscow-Leningrad, 1965–66.
Raikov, I. B. Kariologiia prosteishikh. Leningrad, 1967.