ABSTRACT
This chapter reviews what is known about histone gene organization, messenger RNA structure, protein and deoxyribonucleic acid (DNA) sequences, and regulation of histone mRNA levels. It shows how this might fit into an evolutionary scheme for histone genes with emphasis on the data needed to fill in the model. Histones are the basic proteins which package the DNA in eukaryotic chromosomes. The gene organization described covers only some of the histones in each species. Selective pressure has maintained close linkage of histone genes in all species studied thus far. The histone genes provide an excellent opportunity to study the changes in nucleotide sequences that can occur without altering the protein sequence. A number of sequences of histone genes from a diverse set of species have been determined and in several cases independent genes from the same species have been sequenced. There are a number of different histone gene sequences known from different species.
