Chromatin

Chromatin is a genetic material or a macromolecule comprising of DNA, RNA, and proteins which result in the formation of chromosomes within the nucleus of eukaryotic organisms is termed as chromatin. This chromatin is located within the cell nucleus. The main functions of this material include:

  • Preventing the DNA damage.
  • Tightly packing of the DNA to fit into the cell.
  • Control the DNA replication and gene expression.
  • Support the DNA molecule to permit the process of cell cycle – meiosis and mitosis.

Chromatin

The structure of a chromatin or the so-called nucleosomes resembles the arrangement of string on beads when observed under the light microscope in its elongated method. Each nucleosome comprises of DNA, which is wrapped with eight proteins termed histones. Later, these nucleosomes are enfolded into 30 nm coiled named solenoid. Therefore the presence of additional histone proteins helps in supporting the chromatin structure.

Chromatin Structure

The structure of chromatin is governed by a number of factors. The complete structure mainly depends on the phases of cell cycle. They undergo various structural changes during cell cycle or division. During cell division, the structure of the chromatin and chromosomes are visible under a light microscope, which changes their shape while the DNA is duplicated and divided into two cells.

There are 3 stages in chromatin group:

  1. Nucleosomes are formed by the wrapping of DNA around the histone proteins
  2. Multiple histones wrap into a 30 nm fiber consisting of the nucleosome.
  3. Higher-level DNA packaging of the 30 nm fiber into the metaphase chromosome.

Methods used to Analysis Chromatin:

  • Chromatin Immunoprecipitation Sequencing – A process mainly used for analyzing the interactions of the protein with DNA. The binding sites of DNA combined proteins are identified by the Chromatin Immunoprecipitation and parallel DNA sequencing.
  • Formaldehyde-Assisted Isolation of Regulatory Elements Sequencing-A method mainly used to control the sequences of those DNA regions of the genome, which are related to the regulatory activity.
  • DNase I Hypersensitive Sites Sequencing  – It is mainly used for recognizing the position of monitoring regions, mainly based on the genome-wide sequencing, which is sensitive to cleavage by DNase I.
  • Assay for Transposable Accessible Chromatin Sequencing– A technique mainly used for studying the accessibility of chromatin. ATAC-seq is an opposite method to MNase-seq. Tn5 transposase is used for synthetic transposition into the available regions of the genome.
  • DNA footprinting – A technique mainly used for identifying the DNA-binding protein.
  • Micrococcal Nuclease Sequencing–A method mainly used for studying about the nucleosomes by digesting chromatins. This sequence mainly uses micrococcal nuclease enzyme for identifying the position of the nucleosome throughout the genome.

Difference between Chromosome and Chromatin

The table below shows the main difference between the chromatin and chromosome.

Chromosome Chromatin
Chromosomes are condensed Chromatin Fibers. Chromatin is composed of a nucleosomes-a complex of DNA and proteins.
Chromosomes are compact, thick and ribbon-like. Chromatin fibers are long and thin.
A chromosome is paired. Chromatin is unpaired.
Distinctly visible during cell division. Found throughout the cell cycle.
Visible in light microscope Visible in electron microscope

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A dominant diploid sporophyte is found throughout the life cycle of ___