[The quantity of associated acrocentric chromosomes in human lymphocytes passing through 1st, 2d and 3d mitoses in culture].

The reproductive ability of lymphocytes of peripheral blood with the usage of 5-bromine-deoxyuridine has been studied in 8 healthy children at the age of 5-6 years. Single second mitoses occurred in 48 hour cultures (6.5%), in 72 hour cultures the frequency of the first, second and third mitoses was equal, in 96 hour cultures the third mitoses dominated. Consequent divisions of lymphocytes were accompanied by a decrease in associative acrocentric chromosome, in average by 25%, within one mitotic cycle, while in mitoses of a given ordinal number the frequency of associations did not depend on the duration of cultivation. The fixation of the culture at the 48th hour of cultivation makes it possible to take into account the frequency of associations of acrocentric chromosomes without calculation of the ordinal number of mitosis because of an significant amount of second mitoses at this time, and of a sufficient value of the mitotic index (4.6 +/- 0.5%) necessary for cytogenetic analysis.