Can anyone explain epigenetics?

Question

I came across some notes detailing hereditary traits that are transfered via RNA rather than DNA: a process denoted as epigenetics. This seems to shoot some holes in the central dogma of Mendelian genetics. Can anyone explain what epigenetics is?

Answer 1

Epigenetics is the study of epigenetic inheritance, a set of reversible heritable changes in gene function or other cell phenotype that occur without a change in DNA sequence (genotype). These changes may be induced spontaneously, in response to environmental factors, or in response to the presence of a particular allele, even if it is absent from subsequent generations

Epigenetics includes the study of effects that are inherited from one cell generation to the next whether these occur in embryonic morphogenesis, regeneration, normal turnover of cells, tumors, cell culture, or the replication of single celled organisms. Recently, there has been increasing interest in the idea that some forms of epigenetic inheritance may be maintained even through the production of germ cells (meiosis), and therefore may endure from one generation to the next in multicellular organisms..

hope this helps

Answer 2

It doesn't really create a problem. You can find the very scientific definition in the first answer and also at wikipedia.
The important things about epigenetics are the reversibility and the fact that the DNA sequence is not altered. To put it roughly in simple terms it is about how the state of expression of genes is inherited from one generation to the other.

In wikipedia you can read several examples. I will just highlight one to make things clear.
Imagine that you have a bacterial cell and one of its genes, let's call it gene A, needs some of its own product (protein A) to get activated (this is called a positive feedback loop). Under normal conditions the gene will not be expressed. Let's imagine that expression of gene A can also be activated by a transient signal. Upon such a signal, protein A will be formed activating further the expression of gene A . The daughter cells, since they will "inherit" protein A molecules during the cell division, will be committed to producing protein A even when the signal stops.
This way they "inherit" the pattern of gene expression of the parental cell. However there are mechanisms for reseting/changing the state of the system, so it is not necessary that all the progeny will have the same traits under all conditions.

Answer 3

The study of changes in gene silencing that occur without changes in the genes themselves. Many genes in the body are permanently turned off as part of normal development. But sometimes that process goes awry, turning off genes that should otherwise remain active. This field of study and its associated therapies aims to switch these genes back on. It is a new approach to the treatment of aging, inherited diseases and cancer. It can also be described as the study of heritable changes in gene function that occur without a change in the DNA sequence.
www.abc.net.au/science

Can also be described as the study of the processes involved in the unfolding development of an organism. This includes phenomena such as X chromosome inactivation in mammalian females, and gene silencing within an organism.
It also involves the study of heritable changes in gene function that occur without a change in the sequence of nuclear DNA. This includes the study of how environmental factors affecting a parent can result in changes in the way genes are expressed in the offspring.