As we know DNA is basically composed of four nucleotides -
adenine, thymine, guanine and cytosine and these nucleotides are
joined in various sequences that are highly important for
determining the genetic information that they encode.
Eukaryotic cells encompass large quantity of genetic
information and if the amount of DNA present in these cells are
left unpacked it`s highly impossible to fit it inside these cells
let alone the nucleus.
Therefore DNA gets organized into a highly compact structure by
coiling around histone cores resulting in the formation of
nucleosomes. These nucleosomes are further wrapped around each
other to condense into chromatin fiber. The chromatin fiber
condenses to form chromosomes.