Abstract
Though the chromatid is the functional unit of the chromosome, the pollen-tube chromosomes of Tradescantia show aberrations, following irradiation in very early prophase, which are interpreted in terms of ^-chromatid breaks and rearrangements. Breaks of Va-chromatids include exchange breaks and rotation of a single piece of a broken -chromatid. Further evidence of quadripartite structure is the presence of 4 very thin strands in stretched portions of the chromosome.
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