ISOLATED CHROMOSOMES

Abstract

Methods are described by which cells and nuclei are broken up, and whole isolated chromosomes in quantity are obtained free of other materials. Fish and chick erythrocytes, calf thymus, and mammalian liver are used. Chromosomes thus prepd. may be kept 3- 4 days in saline in the cold. These chromosomes show a definite morphology[long dash]constrictions, trabants, and clearly distinguishable hetero- and euchromatin. Specific chromosomes can be distinguished by their morphology. Coiling of chromonemata can be seen and coils can be relaxed by the same specific treatments known to produce this effect in chromosomes in intact cells. At least 2 chromonemata are coiled together. A drop of such a suspension of chromosomes smeared on a slide stains strongly with the Feulgen technique. These bodies thus isolated are, therefore, intact chromosomes and not merely unspecific nucleoprotein fibers.