Some genes specify the production of proteins, while others specify the production of RNA. In either case, It sometimes occurs that one copy of a gene, even being transcribed as quickly as the RNA polymerase molecules can work, cannot produce enough of its product to satisfy the needs of the cell. Due to the process of gene amplification, certain genes exist in more than one copy within a single cell. Histone proteins, around which the DNA double helix is wound in the nucleosomes, must be produced in large numbers. In a given cell, the combined weight of the histones is equal to that of the cell's DNA. Each major type of histone, of which there are five, accounts for 0.5 to 1% of the total cell protein. In order to produce histone proteins at a high enough rate, the cells of multicellular organisms contain between 50 and 500 copies of...