Chapter CHST1, Problem 1RQ

What are the major mechanisms of epigenetic genome modification?

Summary Introduction

To review:

The major mechanisms of the modification of epigenetic genome.

Introduction:

Epigenetics is a branch of genetics, which studies the changes in the body that are heritable. These changes do not change the DNA (deoxyribonucleic acid) of the organism. The traits that are of epigenetic origin are stable and inherited mitotically as well as meiotically. Thus, these changes bring about changes in the gene expression, without modifying the DNA.

Explanation of Solution

The genome is similar in all the cells of an organism. On the other hand, the epigenome is specific for a cell or varies from cell-to-cell. The traits within the epigenome are transferred to the daughter cells through mitosis and to the offspring by meiosis. The various mechanisms of epigenetic genome modification are described as follows:

1. DNA methylation or demethylation- During transcription, the DNA is methylated at the cytosine. When this methylation or demethylation is reversible, it leads to epigenetic genome modification.

2. Chromatin remodeling- Chromatin is the dense and compact form of DNA, which is bound by the histone proteins. This structure, present within the nucleus is known as a nucleosome. The histone molecule is made up of smaller subunits, which gives it an octameric structure. When the chemical groups are changed attached to the histone proteins, it can lead to epigenetic genome modification.

3. Noncoding RNA (ribonucleic acid) molecules-based gene expression regulation- The micro RNA (miRNAs) and long noncoding RNAs (lncRNAs) are produced during transcription besides mRNA (messenger RNA). The miRNAs control the pattern formation within the developing embryos, physiological processes, and time of development. On the other hand, the lncRNAs bring about epigenetic changes by modifying the chromatin enzymes.

Conclusion

Thus, the epigenetic genome can be modified by three mechanisms, which are reversible DNA methylation or demethylation, chromatin remodeling, and regulation of gene expression by the noncoding RNAs.