Question

Which of the following arrangement is correct ?

• A. DNA -> Nucleosome -> Solenoid -> Chromatin fibre -> Chromatid -> Chromosome
• B. Nucleosome -> Solenoid -> Chromatin fibre -> Chromatid -> DNA -> Chromosome
• C. DNA -> Chromosome -> Chromatin fibre -> Chromatid -> Solenoid -> Nucleosome
• D. DNA -> Solenoid -> Chromatin fibre -> Chromatid -> Chromosome -> Nucleosome

Answer 1

The correct option is D DNA -> Solenoid -> Chromatin fibre -> Chromatid -> Chromosome -> Nucleosome

DNA -> Nucleosome -> Solenoid ->
( 2nm) ( 10nm ) (30nm)
Chromatin fibre -> Chromatid ->
(300nm) ( 700nm)

Chromosome
(1400nm)


Diameter of DNA duplex is 2nm. It coils and form nucleosome that appears as beads on a string.

The beaded string is further coiled to form cylindrical coil or solenoid having 6 nucleosome per turn. The nucleosomal organization has 10nm thickness, which gets further condensed and coiled to produce a solenoid of a 30nm diameter.

This solenoid structure undergoes further coiling to produce a chromatin fibre of 300nm and then chromatid of 700nm.
Therefore option a) DNA -> Nucleosome -> Solenoid -> Chromatin fibre -> Chromatid -> Chromosome is correct