Eukaryotic chromosome structure

Eukaryotic chromosome structure refers to the levels of packaging from the raw DNA molecules to the chromosomal structures seen during metaphase in mitosis or meiosis.

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In eukaryotes the chromosomes are found packaged within a nuclear membrane, unlike the case in prokaryotes. This membrane consists of a DNA double helix bound to an octamer of core histones (2 dimers of H2A and H2B, and a H3/H4 tetramer). Together, the DNA bound around this histone core forms what is known as the nucleosome. About 147 base pairs of DNA coil around 1 octamer, and ~20 base pairs are sequestered by the addition of the linker histone (H1), and various length of "linker" DNA (~0-100bp) separate the nucleosomes. Packaging of DNA is facilitated by the electrostatic charge distrubution: phosphate groups cause DNA to have a negative charge, whilst the histones are positively charged. Most eukaryotic cells contain histones (with a few exceptions) as well as the kingdom archea, a protist group