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Electrophoretic Shift Mutants in Chinese Hamster Ovary Cells: Evidence for Genetic Diploidy
Michael J. Siciliano, Jeanette Siciliano and Ronald M. Humphrey
Proceedings of the National Academy of Sciences of the United States of America
Vol. 75, No. 4 (Apr., 1978), pp. 1919-1923
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/68125
Page Count: 5
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Electrophoretic shift mutants induced in Chinese hamster ovary (CHO) cells indicate that these cells are not extensively functionally hemizygotic. Therefore, effective haploidy is unsatisfactory as a general theory to explain the frequency of recessive mutants in this cell line. CHO cells were screened for electrophoretic shift variants of enzymes coded by ∼ 40 genetic loci. Clones isolated after exposure to ultraviolet radiation were examined by starch gel and Cellogel electrophoresis. Shift variants were recovered for enzymes representing 11 different loci. Variant clones were subcloned to demonstrate the heritability of the variations. Mutants at nine loci produced multiple-banded patterns consistent with the patterns expected of genes at loci represented twice (diploid). Chromosome localization of these diploid loci in other mammalian species where they have been mapped, suggests that they represent a random sample of CHO genes. Chromosome analysis of mutant subclones indicated that the variation did not take place in tetraploid cells. The data indicate that the quasi-diploid CHO cells appear only as functionally hemizygous as would be expected of a slightly hypodiploid cell line derived from an organism in which the haploid number is 11.
Proceedings of the National Academy of Sciences of the United States of America © 1978 National Academy of Sciences