Epigenetics: Unraveling the Complexities of Mutational How it Impacts Gene Expression
What is Epigenetics?
Mutational refers to changes in gene expression or cellular phenotypes caused by mechanisms other than changes in the underlying DNA sequence. These epigenetic modifications regulate how genes are expressed and can be passed from cell to cell as cells divide, and in some cases between generations. The term "mutational" was coined by developmental biologist Conrad Waddington in the 1940s to describe a branch of biology that studies how individuals with identical genetic information develop different phenotypic traits.
DNA Methylation
One of the main Epigenetics mechanisms is DNA methylation. DNA methylation involves the addition of a methyl group to cytosine nucleotides within DNA. In mammals, this occurs most commonly at cytosine-guanine dinucleotide (CpG) sites. The addition of a methyl group to CpG sites often inhibits gene transcription by preventing transcription factors and RNA polymerase from binding to the promoter region of genes. DNA methylation plays a key role in cellular differentiation, X-chromosome inactivation, genomic imprinting, and silencing of parasitic DNA. Abnormal methylation patterns have been linked to diseases such as cancer.
Histone Modifications
Another major epigenetic modification mechanism involves chemical changes to histone proteins. Histones are basic proteins that DNA wraps around to form chromatin and pack into our cells. Histone tails can become chemically modified through processes like acetylation, methylation, phosphorylation, ubiquitination, and sumoylation. These histone modifications alter the accessibility of DNA to transcription factors and gene expression machinery. For example, histone acetylation tends to relax chromatin structure and promote gene transcription, while histone methylation can either enhance or repress transcription depending on which amino acid residues are methylated.
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