Question

define epigenetics and give some examples of what and how it can alter "genetic" information/control

Answer 1

Epigenetics is simply the changes in phenotype with out a change in genotype causing alteration in how cells read the genes.

External modifications in DNA that turn genes on or off with out affecting DNA sequences.

Epigenetic changes alter the physical structure of DNA leads to unusual gene expression.Some of them are given below

☆DNA methylation

Involves the addition of a methyl group, or a "chemical cap," to part of the DNA molecule, which prevents certain genes from being expressed.

Molecules of carbon and hydrogen chemically bind to cytosine, one of the four nucleotide bases in DNA.

Consequence of DNA methylation is the silencing of gene expression.If certain regions of the DNA around genes are methylated that is, if all cytosines carry methyl groups their activity is diminished.

☆Histone protein modification

DNA is packaged around histone proteins, and it forms nucleosomes helping the DNA to organise its structure.

Tails of the histone protein project out from the coils, which is then accessible to local enzymes that can easily modify some of the amino acids in these tails.

Histone modifications leads to the addition of specific marks on individual amino acids. Modifications forms unique combination that modulates the way the DNA is structured.

DNA is either tightly packed making it inaccessible to the machanisms needed to read and express its gene or packed loosely that open its access to the DNA for gene expression.

Histone modifications is significant in determining the gene activity.

☆ Non coding RNAs

Play an important role in the regulation of gene activity because they can target specific mRNA and prevent their translation into proteins.

So make an additional level of regulation not only on the Gene's of DNA but also r on the intermediate RNA molecule resulting from the initial phase of gene expression ie transcription.

Epigenetic changes leads to different disorders such as mental retardation associated disorders, immune disorders, neuropsychiatric disorders and pediatric disorders and many types of cancers.