Please explain packaging of dna helix?

Solution:


DNA are very long molecules of information which needs to be packed inside a tiny cell, so it uses specialized group of proteins-histones. Eight histone proteins come together to form a nucleosome core particle which coil the DNA tightly to reduce there size so as to fit them in the cell.

The first level of packaging involve the nucleosome to which the DNA is tightly wound around it where H1 linker brings it more closer to it where the length of the fibre becomes 11 nm. The second level involves very tightly packaging of the DNA fibre where the diameter becomes 30 nm.  It is also called as solenoid model in which they are coiled and arranged in a zigzag pattern. he next level involves the packaging of 30 nm fibres which are anchored by the scaffold proteins and form a 300 nm structure of the fibre. Finally the fibre become 700 nm and 250 nm width structure and called as a chromosome (highly condensed state). 


 

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