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the presence in the nucleus of certain somatic cells of giant multifilamentous (polytene) chromosomes, which are hundreds of times larger than normal chromosomes. Polyteny leads to substantial increase in ploidy of the nuclei (up to 32.768N in Chironomus). Polyteny was first described in 1881 by the French cytologist E. Balbiani. Polytene chromosomes are observed in the cells of larvae of a number of Diptera (Chironomus, Drosophila), in Protozoa, and in some plant cells. Polyteny is the result of repeated replications of chromosomes without subsequent divsion of the cell or its nucleus. Giant chromosomes are characterized by specificity of location of the cross-bands, which permits compilation of chromosome maps and study of the functional activities of each band or group of bands.
REFERENCESLobashev, M. E. Genetika, 2nd ed. Leningrad, 1967. Swanson, C, T. Merz, and W. Young. Tsitogenetika. Moscow, 1969. (Translated from English.)
M. M. ASLANIAN