Chromatin – what makes up our DNA? 9th September 2024 – Tags: chromatin, Chromosome, DNA, proteins
When we come across scientific literature describing the subject of genetics and cellular structure, we can notice the term chromatin. Despite the name being very similar to chromosomes, it is a separate unit. What is chromatin and what is its purpose? How can we perform analyses on chromatin?
What is chromatin?
Chromatin is a complex of DNA and proteins that together form chromosomes in the nucleus of eukaryotic cells. At the beginning of research, it was said to be just a colored substance contained in the cell nucleus, but later it was characterized as proteins attached to DNA. In summary, it is a genetic material or macromolecule containing DNA, RNA and related proteins that form chromosomes in the nucleus of a eukaryotic cell.
Chromatin functions in the cell nucleus:
• Protection from DNA damage
• Tightly packing DNA so it can fit into the cell
• Control of DNA replication and gene expression
• Support for the DNA molecule to allow the cell cycle – meiosis and mitosis – to proceed
Chromatin structure:
The structure of chromatin resembles the arrangement of beads on a string, with each nucleosome containing DNA, which is then surrounded by eight proteins called histones. The complete structure depends mainly on the phases of the cell cycle, as cells undergo various structural changes during cell division.
Chromatin analysis methods:
• Chromatin Immunoprecipitation Sequencing – a process used to study protein interactions with DNA
• Formaldehyde-assisted isolation of regulatory elements – a method used to control the sequence of those DNA fragments that are associated with regulatory activity
• DNase I hypersensitive site sequencing – a process used to recognize the position of monitored regions, mainly based on whole genome sequencing
• Transposable accessible chromatin sequencing assay – a method used to study chromatin accessibility
• DNA Footprinting – a technique used to identify DNA binding protein
• Micrococcal nuclease sequencing – a method used to study nucleosomes by digesting chromatin
Chromatin and chromosomes:
Despite their rather similar names, the two forms of DNA packaging described differ from each other in many aspects.
• Presence in the cell – This protein is present throughout the cell cycle, and the chromosome is best visible during cell division
• Visualization method – This protein is visible under an electron microscope, and the chromosome under a light microscope
• Appearance – This protein has a long and narrow shape visible in the cell nucleus, while the chromosome is more complex and thicker, visible during cell division
• Pairing – This proteins does not occur in pairs, but the chromosome does
• Visibility – This protein can be seen during the interphase of the cell nucleus, and the chromosome during the M phase of the cell cycle
• Function – This proteins helps DNA replicate, and the chromosome acts as a transmitter of genetic information
• Condensation – This protein is insufficiently condensed, while the chromosome is a condensed molecule
