Nucleus = site of storage for genetic material to be replicated/expressed. Often om studded w/ rb and attached to er. Nuclear lamina = dense meshwork (made up of lamins = intermediate filaments), lies on inner surface of nuclear envelope, disintegrates during mitosis and results in phosphorylation j mechanical support for envelopes and site of attachment of chromatin. Nucleus has major control j e. g. hela cells: contain 10,000,000 ribosomes: single nucleus has to import 560,000 proteins and import 14,000 rb subunits every minute. Proteins that enter nucleus have nuclear localization signal j stretches of positively charged aa j function as. Proteins that move out have nuclear export signals. l-gtp release w/ hydrolysis j needs accessory ran-gap1. Only about 5% of human dna encodes functional rnas and proteins chromosomes = made of dna and associated proteins (nucleoprotein) = chromatin. 2 types of proteins in chromatin: 1) histones = most abundant in chromatin, small basic proteins.