INCORPORATION OF 5-IODODEOXYURIDINE INTO DNA OF PLANT CELLS

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Abstract
Incorporation of 5-iododeoxyuridine into the DNA of root tip chromosomes of Vicia faba is demonstrated by Tritium label introduced with the iodinated analogue is detectable exclusively over nuclei of interphase cells and specifically over chromosomes in dividing cells. No grains are found over nucleoli. The number of grains per nucleus is approximately halved after one division cycle and quartered after 2 divisions. Incorporation of the iodinated analogue was demonstrated by use of an I131 label. CsCl density gradient centrifugation of extracted native DNA, following 24 hr treatment with IUdR, reveals a new heavier component attributable to replacement of thymine methyl groups by iodine. The degree of thymidine replacement by IUdR in the IUdR-containing strands was calculated to be about 22%, and slightly greater (28%) if FUdR was included in the treatment solution.