Solenoid Structure Related to Chromatin Fiber

Chromatin is a complex of DNA and proteins that form the genetic material of eukaryotic cells. It is organized into a hierarchical structure to fit into the small space of the nucleus. The solenoid structure is related to the organization of chromatin fiber.

What is a Solenoid Structure?

A solenoid structure is a helical structure formed by a DNA molecule wrapped around a histone octamer. The histone octamer is made up of two copies of four different histone proteins: H2A, H2B, H3, and H4. The DNA molecule is wrapped around the histone octamer two times, forming a nucleosome. The nucleosomes are then further coiled into a solenoid structure, which is a compacted form of chromatin fiber.

Role of Solenoid Structure in Chromatin Organization

The solenoid structure plays a crucial role in the organization of chromatin fiber. It helps to compact the DNA molecule into a small space, thereby allowing it to fit into the nucleus of the cell. It also helps to regulate gene expression by controlling access to the DNA molecule. The solenoid structure can be remodeled by chromatin remodeling complexes to allow or restrict access to the DNA molecule.

Conclusion

In conclusion, the solenoid structure is related to the organization of chromatin fiber. It is formed by the wrapping of DNA around a histone octamer and further compaction of nucleosomes. The solenoid structure plays a critical role in the regulation of gene expression and the organization of chromatin in the nucleus.

The solenoid defines the packing of DNA as a 30nm fibre of chromatin and results from the helical winding of at least five nucleosome strands. The nucleosomes resemble beads on a string, are further compacted into a helical shape via the NH2 terminal protein interactions of the octameric histones, called as a solenoid. DNA packed into solenoids, unlike DNA in nucleosome form, is not transcriptionally active. With more packing, solenoids are able to become increasingly more packed, forming chromosomes. At this point, solenoids coil around each other to form a loop, followed by a rosette, then a coil, and at last, two chromatids. The end result is the metaphase chromosome. The completely condensed chromatin has a diameter of up to 700 nm.