Question

Epigenetics centres on inheritable phenotype changes that do not involve alterations in the DNA sequence, indicating the influence of environmental factors. Based on content covered in lectures, discuss the mechanisms implicated in the inheritance of epigenetic information.

Answer 1

Epigenetics is the study of heritable changes in gene activity that do not involve in alterations to the genetic code.  Epigenetic changes alter the physical structure of DNA, for a example,a change is DNA methylation is the addition of a methyl group, or a "chemical cap," to part of the DNA molecule, it prevents certain genes from being expressed.Transgenerational epigenetic inheritance is the transmission of epigenetic markers from one organism to the next that is parent–child transmission that affects the traits of offspring without alteration of the primary structure of DNA means the sequence of nucleotides. Lifestyle includes different factors such as nutrition, behavior, stress, physical activity, working habits, smoking and alcohol consumption. Environmental and lifestyle factors may influence epigenetic mechanisms. DNA in the mother's egg cells were still present in the embryo after fertilization, even though other epigenetic marks are erased. "This indicates that the mother passes on her epigenetic marks to her offspring..Epigenetic modifications, such as DNA methylation, can contribute to alter gene expression in heritable manner without affecting the underlying genomic sequences.

The major epigenetic mechanisms include as DNA methylation and hydroxymethylation; histone protein posttranslational modifications, and noncoding RNA regulation; and RNA editing.

DNA methylation is a process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts to repress the entire gene transcription.

Cytosine hydroxymethylation was as another important epigenetic modification on DNA.Similar to methylation, hydroxymethylation replaces, at the C5-position in cytosine, the hydrogen atom by a hydroxymethyl group.

Histone post-translational modifications are covalent modifications of histones by phosphorylation on serine or threonine residues, methylation on lysine or arginine, acetylation and deacetylation of lysines, ubiquitylation of lysines and sumoylation of lysines.

A non-coding RNA (ncRNA) is a functional RNA molecule that is transcribed from DNA but not translated into proteins. Epigenetic related ncRNAs include miRNA, siRNA. In general, ncRNAs function to regulate gene expression at the transcriptional and post-transcriptional level.

RNA editing is a molecular process through which some cells can make discrete changes to specific nucleotide sequences within an RNA molecule after it has been generated by RNA polymerase. RNA editing may include the insertion, deletion, and base substitution of nucleotides within the RNA molecule.

These are the major mechanisms of epigenetic inheritance mechanisms.