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DNA is wrapped around proteins called histones, to form nucleosomes. Each nucleosome is a histone octomer composed of (H2A, H2B, H3, and H4) subunits with a 1.65 helical turn of 147 nucleotide bases. Nucleosomes then fold upon themselves to form chromatin.
Loosely packed Chromatin called euchromatin is assoicated with high gene expression whereas densely packed chromatin called heterochromatin is associated with transcriptional repression (gene silencing).
During metaphase stage of mitosis and meiosis chromatin becomes supercoilded resulting in the ability to see chromosomes under a microscrope. This is essential for the seperation of DNA between daughter cells.
Ribosomes translate (read) messenger RNA to produce specific polypeptide chains (proteins).
The Ribosome itself is made up rRNA which forms the structures which read the messenger RNA and add peptides to the polypeptide chain.
There are also a number of proteins associated with the ribosome which increase its stability and efficiency.
DNA is the medium which encodes the information that makes an organism what it is. DNA usually forms a double stranded structure and encodes genes and other regulatory elements.
RNA can act as either catalyst like proteins, a store of information like DNA, or both. mRNA is produced when the DNA of a cell is read by specific enzymes (RNA polymerase) and is then itself read by ribosomes to produce proteins. Hence earning its name of messenger RNA.