How is the chromosome structured through the packaging of the $DNA$ helix? Describe in detail.

(N/A) Taking the distance between two consecutive base pairs as $0.34 \, nm$ $(0.34 \times 10^{-9} \, m)$,if we calculate the length of $DNA$ in a typical mammalian cell with a double-helical structure by multiplying the total number of base pairs by the distance between two adjacent pairs,i.e.,$6.6 \times 10^9 \, bp \times 0.34 \times 10^{-9} \, m/bp$,it is approximately $2.2 \, m$. This length is much greater than the dimensions of a typical nucleus (approximately $10^{-6} \, m$).
In $Escherichia \, coli$ $(E. \, coli)$,the length of $DNA$ is $1.36 \, mm$ with $4 \times 10^6 \, bp$.
Although $E. \, coli$ lacks a well-defined nucleus,the $DNA$ is not scattered throughout the cell. The negatively charged $DNA$ is held in a specific region with the help of some positively charged proteins,which is called the nucleoid.
In the nucleoid,$DNA$ is organized in large loops held by proteins.
In eukaryotes,this organization is much more complex. It involves a set of positively charged proteins called histones.
Proteins acquire their charge based on the abundance of amino acids with charged side chains.
Histone proteins are rich in the basic amino acids lysine and arginine,both of which carry a positive charge in their side chains.
An organized unit of eight histone molecules is called a histone octamer. The negatively charged $DNA$ wraps around the positively charged histone octamer to form a structure called a nucleosome.
Nucleosomes constitute the repeating unit of a structure in the nucleus called chromatin,which appears as 'beads-on-string' under an electron microscope.