The Synthesis of Deoxyribonucleic Acid and Nuclear Histone of the X Chromosome of the Rehnia Spinosus Spermatocyte

Abstract

The X chromosome of the Rehnia spinosus (Orthoptera) spermatocyte exists in a vesicle separate from the rest of the nucleus during its replication. This chromosome is typically heterochromatic, and late replicating. After replication the chromosome vesicle fuses with the nucleus. Cytophotometric determination of DNA and histone during replication of the chromosome revealed two types of histone. One class increases in amount in proportion to the DNA. The second class remains constant as DNA doubles, and probably increases later. Autoradiographic studies of incorporation of amino acids indicates that histone labelling occurs during chromosome replication. However, a lag in amino acid incorporation suggests that DNA replication in the X chromosome, while accompanied, or closely followed, by complexing with histone, is not necessarily coupled with its synthesis.