Autosegregation of enzyme loci in agamospermous progenies of triploid plants of sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.) |
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Authors: | E V Levites S S Kirikovich |
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Institution: | 1.Institute of Cytology and Genetics,Siberian Branch of the Russian Academy of Sciences,Novosibirsk,Russia |
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Abstract: | The ratios of the phenotypic classes of glucosephosphate isomerase (GPI2) and malate dehydrogenase (MDH1 and MDH2) were studied
in agamospermous progenies of triploid sugar beet plants. The ratio of the phenotypic classes of these enzymes corresponds
to the calculations based on the assumption of polyteny of chromosomes carrying alleles of the enzyme loci accompanied by
the loss of extra copies of the alleles in the first division of a cell entering embryogenesis. An increase in the gene dosage
due to polyteny leads to the appearance in the progeny with a definite frequency of alleles that were absent in the original
parental plant. The notions of “meiotic autosegregation” and “mitotic autosegregation” characteristic of meiotic and mitotic
agamospermy are introduced, as well as the term locus polygenotype characterizing not only the allelic composition and the number of chromosomes, but also the number of chromatids carrying
alleles of the marker locus in the cell before its entry into embryogenesis. |
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