Spiralization of Chromosomes

Spiralization of Chromosomes 

the shortening and thickening of chromosomes during cell division. Spiralization promotes the normal separation of chromosomes to the poles of a cell. It is caused by an increase in the diameter of the coiled nu-cleoprotein threads—chromonemata—that comprise the chromosome, as well as by a shortening of the coil pitch. It was first described in 1880 by the Russian scientist O. V. Baranetskii, who studied the periodicity and reversibility of spiralization during the cellular cycle in spiderworts.

In some protozoans the spiral structure of chromosomes is preserved even during interphase. The number of coils in the spiral of a chromonema is constant for each chromosome, while the direction of coiling within sister chromatids and within chromosome arms may be clockwise or counterclockwise. The rate of spiralization is different in different parts of a chromosome, depending on the structural and functional characteristics of the parts. This results in regular changes in the morphology of chromosomes during various stages of mitosis or meiosis.

REFERENCES

Prokof’eva-Bel’govskaia, A. A. “Mikroskopicheskoe stroenie khromosom.” In Rukovodstvo po tsitologii, vol. 2. Moscow-Leningrad, 1966.
“Differentsial’naia spiralizatsiia i khromosomnyi analiz.” Tsitologiia, 1974, vol. 16, no. 3.
Ohnuki, V. “Structure of Chromosomes,” part 1: “Morphological Studies of the Spiral Structure of Human Somatic Chromosomes.” Chromosoma, 1968, vol. 25, issue 3.

A. B. IORDANSKII