Human genome about 3 x 10^9 base pairs long. Human dna must be condensed by about 10,000 fold to fit inside nucleus two copies of each chromosome per cell about 2m of dna in each cell. Best analogy for most fundamental unit of packaging of dna double helix: ball of twin no because can"t get at first bit of twin, string of beads, spool of thread, bowl of spaghetti, telephone. Despite dna being condensed, dna must remain available for replication, repair, and gene transcription. Eukaryotic dna condensed with help of specialized proteins chromatin. Bacteria condense dna but in a different way. Primary eucaryotic proteins involved in condensing dna (prokaryotes use different proteins) small proteins contain fewer than 200 aa rich in lysine and arginine residues (+ charged to interact with negatively charged dna) Lysine and arginine can become protonated and be positively charged at physiological ph ideally suited to interact with negatively charged phosphate of.