The human genome is abut 3 x 1019 base pairs long. At 0. 34 nm per base pair, that"s 102 cm. Human dna must be condensed about 10,000 - fold to fit inside the nucleus. Despite being condensed, dna must remain available for replication, repair and gene transcription. Eukaryotic dna is condensed with the help of specialized proteins. Eukaryotic proteins involved in condensing dna (bacteria use different proteins) Highly conserved among eukaryotes, reflecting their important function. Two copies each of histones h2a, h2b, h3 and h4. The double helix wraps around the histone octamer 1. 7 times (146 base pairs) Histone octamers with dna are called nucleosome core particles. Core particles are linked by stretches of dna 3-80 base pairs long. A nucleosome consists of a core particle and one adjacent linker region. Structure still controversial - many different packing patterns. Dna has been compacted by a factor of about 100.