Chromosomal structures
Chromosomal Structures
Eukaryotic Chromosomes are composed of DNA, Histone and nonhistone proteins Histones:H1 H2A. H2B.H3.H4. The later 4 form nucleosomes(100 A) and thus called core histones. H1 plays a role in forming 300 A superhelix Histones are rich in basic amino acids Nonhistone proteins play a variety of functions
Eukaryotic Chromosomes are composed of DNA, Histone and Nonhistone Proteins • Histones: H1, H2A, H2B, H3, H4. The later 4 form nucleosomes (100 A) and thus called core histones. H1 plays a role in forming 300 A superhelix • Histones are rich in basic amino acids • Nonhistone proteins play a variety of functions
TABLE 1 1. 1 Some Molecular Characteristics of the Histone Proteins Found in Calf Thymus* Histone Basic/Amino Acids Molecular Weight Total Amino acid residues H1 54 23,000 224 H2A 14 13,960 129 H2B 1.7 13,774 125 1.8 15,273 135 2.5 11,236 102 .Note the small size of the histones; in addition, their predominantly basic amino aaid constitution ensures that they will be positively charged in physiological conditions
Nucleosomes H2B H4 H2A H3 Linker dnA Linker DNA
Scaffold: the structural backbone, can be revealed after mild treatment of the chromosome
Scaffold: the structural backbone, can be revealed after mild treatment of the chromosome