Histones are proteins rich in lysine and arginine residues and thus positively-charged.
For most of the life of the cell, chromosomes are too elongated and tenuous to be seen under a microscope. These duplicated chromosomes are called dyads . When first seen, the duplicates are held together at the centromere . While they are still attached, it is common to call the duplicated chromosomes sister chromatids , but this should not obscure the fact that each is a bona fide chromosome with a full complement of genes. Staining with the trypsin-giemsa method reveals a series of alternating light and dark bands called G bands .