Epigenetics

[vineyridge]

I'm trying to learn about them and don't have the biochemical/genetic background to make much sense out of the scientese.

Could someone direct me to explanations that would make sense to the layperson? The part of epigenetics that keeps liver cells liver cells and skin cells skin cells isn't the part that would affect phenotype differences in identical twins. And that's the part that is of interest.

I've tried to comprehend several articles about the science but find them very heavy going.

[Bast]

I'm trying to learn about them and don't have the biochemical/genetic background to make much sense out of the scientese.

Could someone direct me to explanations that would make sense to the layperson? The part of epigenetics that keeps liver cells liver cells and skin cells skin cells isn't the part that would affect phenotype differences in identical twins. And that's the part that is of interest.

I've tried to comprehend several articles about the science but find them very heavy going.

Here is a very brief description of epigenetics:

According to researcher Susan L. Ewart College of Veterinary Medicine, Michigan State University, USA there are many ways in which genes and the environment interact. "The environment can have a direct impact on DNA, for example, ionizing radiation and reactive oxygen species directly damage exposed DNA, resulting in the initiation of DNA repair mechanisms, which may or may not be fully successful. More recently, it has become clear that the environment can also alter DNA in ways that do not interrupt the DNA strand or change nucleotide sequence. Termed "epigenetics," these mitotically or meiotically heritable DNA modifications result in changes in gene expression, as epigenetic changes typically make DNA sequence unavailable for transcription and thus modified genes are effectively "silenced." Epigenetic changes include DNA methylation, histone modifications (methylation, acetylation, phosphorylation, and ubiquitination), genomic imprinting, and X-chromosome inactivation" states Ewart.

http://www.scienceofmotion.com/documents/equinegenetics.html

[xfactor fan]

Ok, to translate the gene geek speak.

This refers to the fact that while Mendel's laws apply to gross chromosome assortment--you still get half your chromosomes from each parent, and if you are XX, you are female, and YX male. There are a few wrinkles in the system.

Apparently genes can hide, for lack of a better word in sections of the chromosome that are considered junk. Non coding--not functional. Something happens then Poof!! Genes that have never been seen before switch on and start working.

There's also the maternal/paternal fight, where each genome works to maximize the transmission of traits. For example, it is to the male benefit to have lots of large at birth offspring. No matter what it does to the birthing female. Females need to have relatively small easy to give birth to offspring that don't damage the reproductive tract, so they can have more offspring later.

The Discover magazine had couple of articles on this subject. One lab found mice that had been inbred for white coats for lots of generations, had unexpected coat colors show up when the feed was changed. Producing colored offspring. Was quite a shock to the researchers. Talk about fence jumpers! And yes, these mice with brown coats were the offspring of pure breeding white mice. And they could repeat the experiment and get the same results.

Another study has linked diet to type 2 diabetes. Folks that don't have a history, turn up diabetic,

Related to this question is inbreeding in harem species like horses. Given the breeding pattern, few males breed, most females breed, are large numbers of male donated genes being switched off? Thus preserving genetic diversity through the female lines? Historically there have been a couple of male bottlenecks Eclipse, and St Simon come to mind, plus of course our current stallion of doom the dread P.

The breed survived Eclipse, and it survived St Simon. It is likely to survive P. too.

If you've ever studied embryonic development, pretty much all embryos look alike. And human embryos undergo all sorts of stages, looking like amphibians, then reptiles then mammals. So clearly all those genes are present in each of us. So at some point the genes are switched on, then switched back off. And mostly we don't look like lizards, or have scales or fins or gill slits.

This differs from a mutation in that with mutation there is a change in the sequence of base pairs. Here there are no base pair substitutions, but genes that have been in storage suddenly start working.

Hope this helps.

[vineyridge]

Xfactor Fan, that's the first explanation that makes sense to this ignoramus. Thank you so much.

Seems to make breeding even more of a crapshoot, though. I wonder if modern humans will last long enough to understand all this fully and be able to exploit it.

[xfactor fan]

You are welcome.