What is central dogma and describe the packing of $DNA$ helix?

(N/A) Francis Crick proposed the Central Dogma in molecular biology, which states that genetic information flows from $DNA \to RNA \to$ protein.
In some viruses, the flow of information is in the reverse direction, that is, from $RNA$ to $DNA$.
Taking the distance between two consecutive base pairs as $0.34 \, nm$ $(0.34 \times 10^{-9} \, m)$, if the length of the $DNA$ double helix in a typical mammalian cell is calculated (by multiplying the total number of $bp$ with the distance between two consecutive $bp$, i.e., $6.6 \times 10^9 \, bp \times 0.34 \times 10^{-9} \, m/bp$), it is approximately $2.2 \, meters$.
This length is far greater than the dimension of a typical nucleus (approximately $10^{-6} \, m$).
In prokaryotes, such as $E. coli$, although they do not have a defined nucleus, the $DNA$ is not scattered throughout the cell. $DNA$ (being negatively charged) is held with some proteins (that have positive charges) in a region termed as 'nucleoid'. The $DNA$ in the nucleoid is organized in large loops held by proteins.
In eukaryotes, this organization is much more complex. There is a set of positively charged, basic proteins called histones. A protein acquires charge depending upon the abundance of amino acid residues with charged side chains. Histones are rich in the basic amino acid residues lysines and arginines. Both these amino acid residues carry positive charges in their side chains.