What is inside a chromosome?

We have already studied the definitions of chromosome, genome, and DNA in the previous blogs. Now, let us have a look on what is there inside the chromosome.

Each human cell contains 46 chromosomes except eggs and sperms, and which is present inside the nucleus. 23 chromosomes come from the father and other 23 chromosomes from the mother. The DNA associated with histone proteins are wrapped inside the structure called chromosome and it is replicated in the time of cell division. These chromosomes are visible under microscope only during the cell division! 

Why the DNA packaging is so important? Chromosome has plethora of genetic information which stored in DNA. If the DNA present in a cell uncoil, it comes to six feet long!

 Related Terms:

• Histone - These are the proteins which helps the DNA packaging inside the cell's nucleus. Moreover, which helps the DNA to condenses in chromatin. These proteins are rich in lysine and arginine. 
• Nucleosome - It is the repeating unit of chromatin. DNA along with histone proteins form nucleosome. The core histones such as H3, H4, H2A and H2B form H3-H4 tetramer and H2A-H2B dimer. The negatively charged DNA wraps around the positively charged histone octamer. As an outcome, the nucleosomes are stabilized. 
• Chromatin - Nucleosomes packed together to form chromatin. The chromatin loops fold around each other to form chromosome.
• Centromere - The structure which holds the sister chromatids together. Each chromosome has two p and q arms which held together by centromere.
• Telomeres - The repetitive sections of DNA present at the end of each eukaryotic chromosome, which plays a vital role in chromosome replication and maintenance. Telomeres protect the chromosome from becoming impaired. During each cell division, some part of telomeres may lose in some of the cells. If the telomeres completely gone, the cell dies.

References:

• The Jackson Laboratory. (n.d.). Minute to Understanding: What is a chromosome? https://www.jax.org/news-and-insights/minute-to-understanding/what-is-a-chromosome.
• What is a chromosome? (2016, January 25). Yourgenome. https://www.yourgenome.org/facts/what-is-a-chromosome.
• NHGRI. (2019, March 9). Chromosomes Fact Sheet. Genome.Gov. https://www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet.

Thank you!