Thread: Epigenetics

In a lecture on genetics the lecturer mentioned briefly about epigenetics. She explained it was based upon differences between maternal & paternal genotypes and that the phenotype of the offspring would be determined by genomic imprinting...

What was she on about? What exactly is imprinting, how can it be switched on or off and what exactly does epigenetics explain/aim to discover???

Instead of typing all that in, you could have hit the Google button and searched for it, if it is anything to do with science you'll find an explanation on the web. we aqre happy to discuss even educate but yu should do a little research first.

You know i am very interested in this topic lately, but i too am still trying to figure it out. Basically epigenetics is individual to every single person on this planet. It has to do with the methylation of your DNA, either activating or deactivating a certain gene or genes based on methylation on certain sites on the strands. Based on your environment this epigenetic code will change, thus adapt. For instance, lets say you use a certain drug frequently, this may influence the plasticity or activity of a cell so that it may increase this methylation and thus change the expression patterns of lets say neuron DNA. Now what it is that i do not understand is the mechanism by which methylation of DNA occurs, in terms of the pathway more than the chemistry. Do transcription factors play a role? how does plasticity and DNA methylation co-exist, or is it that i have this concept completly wrong? please let me know cause i am self-reviewing. I am interested in how and if you can reverse this pathway, and thus manipulate DNA to have the proper expression patterns in specific cell types. I also am curious how this pathway relates to behaivoral changes due to prolonged illicit drug, therapeutic agent, and toxin exposure.

Megabrain: point taken but I really just want an excuse to discuss this because I know it's interesting!

Yeah Im not too sure about the mechanism of methylation but I think it may just be spontaneous, however, it couldnt be if there is a heritability factor involved. It only occurs to a low percentage of C-Gs on the double helix, I know that much!

What I know about epigenetics:

It is any alteration, above the level of DNA sequence, that is heritable. As was already mentioned, there is methylation of nucleotides, but it is not restricted to that. Alterations to histones, and other DNA associated proteins, can also be inherited. This includes - phosphorylation, methylation, ubiquitination, etc.

In Bacteria:

Methylation of the DNA is used as a primitive immune system agains invading bacteriophage. The bacteria contain restriction enzymes that will cut the DNA at specific sequences (eg - EcoRI). To protect themselves, the bacteria have methylases (eg - DAM) which add a methyl group onto a nucleotide so that the restriction enzyme will not recognize the sequence and "chop up" self DNA. An invading phage would usually lack the methyl group and its genome would be destroyed before it could truly infect the cell.

Also, newly replicated DNA would only have the original strand being methylated, this is called "hemi-methylated". After replication, there is enzymes that "scan" the DNA for mis-matches. When they encounter a mismatch, the enzyme will use the strand with the methyl group (this is the original template) as the 'correct' nucleotide and ensure that it is repaired.

In higher organisms:

Maternal and paternal imprinting is quite interesting. Last semester I learnt all about the mechanisms for it ... but I found it to be quite boring. Essentially, in males and females there is a differential methylation. This methylation remains in somatic cells, but in the germ lines it is removed so that a females germ line cells will only contain the female imprinting.[/u]