What are nucleosomes ? What are they made of ?

Explanation

Under electron Microscope, chromation appears as "beads on string". These beads are known as Nucleosomes. A typical nucleosome: contains 200 bp of DNA double helix wrapped around a core of histone octamer having two copies of each of four types of histone proteins viz H2A, H2B, H3 and H4. H1 Histone lies outside the nucleosome core and seals the two turns of DNA by binding at the point where DNA enters and leaves the core. The DNA continues between two nucleosomes is called linker DNA.