Essay !12 - Epigenomics Code : KSI0024

Genomics Essay # 12- Epigenomics

Sangin Kim

 

<The DNA is not your destiny>

Epigenomics is the study of the complete set of epigenetic modifications on the genetic material of a cell, known as the epigenome. Epigenetic modifications are reversible modifications on a cell’s DNA or histones that affect gene expression without altering the DNA sequence. Epigenomic maintenance is a continuous process and plays an important role in stability of eukaryotic genomes by taking part in crucial biological mechanisms like DNA repair. Two of the most characterized epigenetic modifications are DNA methylation and histone modification.

 

The first epigenetic modification to be characterized in depth was DNA methylation. As its name implies, DNA methylation is the process by which a methyl group is added to DNA. The enzymes responsible for catalyzing this reaction are the DNA methyltransferases (DNMTs). While DNA methylation is stable and heritable, it can be reversed by an antagonistic group of enzymes known as DNA de-methylases. In eukaryotes, methylation is most commonly found on the carbon 5 position of cytosine residues (5mC) adjacent to guanine, termed CpG dinucleotides.

In eukaryotes, genomic DNA is coiled into protein-DNA complexes called chromatin. Histones, which are the most prevalent type of protein found in chromatin, function to condense the DNA; the net positive charge on histones facilitates their bonding with DNA, which is negatively charged. The basic and repeating units of chromatin, nucleosomes, consist of an octamer of histone proteins and a 146 bp length of DNA wrapped around it. Chromatin packaging of DNA varies depending on the cell cycle stage and by local DNA region. The degree to which chromatin is condensed is associated with a certain transcriptional state. Unpackaged or loose chromatin is more transcriptionally active than tightly packaged chromatin because it is more accessible to transcriptional machinery. By remodeling chromatin structure and changing the density of DNA packaging, gene expression can thus be modulated.

 

References

1. https://www.youtube.com/watch?v=zcJPXISDxkM

2. https://www.youtube.com/watch?v=D9CzvalZ2zY

3. https://www.youtube.com/watch?v=Udlz7CMLuLQ

4. https://www.youtube.com/watch?v=LWQfe__fNbs

5. https://en.wikipedia.org/wiki/Epigenomics