The initial stage of packaging have the binding of the chromosomal DNA to histones. Whole, in chromosomes the ratio of the DNA to histones on a weight basis is around 1:1. There are five main types of histones called as H1, H2A, H2B, H3 and H4. Histones are very basic proteins; about 25 percent of their amino acids are lysine or arginine so histones have a vast number of positively charged amino acid side-chains. These positively charged groups therefore bind to the negatively charged phosphate groups of DNA. Not surprisingly giving their importance in packaging DNA the amino acid series of histones have been highly conserved in evolutio.