The Fine Structure of Chromosomes in Pollen Mother Cells of Tradescantia reflexa

Abstract

Studies were made on the fine structure of chromosomes by using both ultrathin sections and whole mounts of chromosomes in the pollen mother cells of Tradescantia reflexa. Chromatin threads of 100Å, 300Å, 1000Å and 3000Å were seen in the chromosomes. The 300Å-chromatin thread seems to be the basic thread of the chromosome. The 1000Å-chromatin thread consists of at least four 300Å-chromatin threads and the 3000Å-chromatin thread (chromonema) is formed by coiling of 1000Å-chromatin thread.
The 300Å-chromatin thread is formed by coiling of a 100Å-chromatin thread, consisting of DNA-histone complex. The DNA double helices may be encircled with, or embedded in histone. The constitution of the DNA-double helices enveloped in histone is discussed.