Ok, I took "I guess" to mean you had some background on the subject and weren't just making assumptions out of thin air, so was wondering what you had read or whatever. That said, let's understand that epigenetics is about changes that occur to the genome at a germline level and within the developing embryo - we are talking about modifications that an individual accumulates through their lifetime that may effect their offspring.

Environmental factors do not automatically go hand in hand with epigenetic modifications. Epigenetics refers very specifically to two main process that control chromatin remodelling - histone modifications and DNA methylation status.

Epigenetic control does not change the genes you were born with.

For a quick beginners guide, perhaps you would find Wiki useful?

http://en.wikipedia.org/wiki/Epigenetics

The lactase gene you talk of (I'm guessing you have Asian parentage?) - this is not an example of epigenetic control, it's simply down to SNP's (genetic polymorphisms) within a population? Unless I'm thinking of something else? In what way has environmental effects in your lifetime caused this? You would have been born with it?

Finally - yes and no. Cancer is a very complicated subject and yes environment factors play a role, such a exposure to carcinogenic compounds giving rise to cancers. However, if I was exposed to a carcinogen, and then developed cancer due to a somatic cell mutation, this has absolutely nothing at all to do with epigenetics but everything to do with environment. The terms "epigenetics" and "environmental effects on genes" are not the same and are not interchangable - make sense?

This of course is purely my opinion based on the fact that I study this stuff for a living and hold a PhD in the subject. teehee

perhaps in terms of frequency but is it not also true that by outcrossing we run the risk of introducing a delterious gene to a previously unaffected population ...

perhaps in terms of frequency in the original affected population but is it not also true that by outcrossing we run the risk of introducing a delterious gene to a previously unaffected population ...

Yes, absolutely Bijou. This is why we need to talk specific examples and not as mass generalisations.

This would be entirely dependent on, for example, the transmission method of the specific gene, is it inherited in a dominant or recessive fashion, or otherwise, is it X-linked.....we need to question penetrence, signalling pathways involved, linkage, other gene effects on expression, the list goes on. OF course is the mutation somatic? Etc etc etc!

So many variables and absolutely why we cannot make sweeping statements like crossbreeds are healthier than pedigrees or vice versa. Inbreeding depression is just but one example I was explaining for genetic fitness - it is in no way whatsoever the be all and end all of the story.

All we can do is make comparisons between specific populations or, specific individuals.

Glad we are on the same wavelength here.

ahh ...but meanwhile decisions about breeding need to be made and the practicalities are that it is safer to breed with what you know about your breed and your lines - for example the bitch I'm planning to breed next has a dog in her pedigree that if doubled up on may produce monorchidism ...there appears to be no epilepsy, good hips and eyes, great temperaments and excellent construction and type, so I only need to focus on looking for a stud dog that always produces entire males...simples !

However if I outcrossed to a different breed whose background and lines I did not know as much about I am effectively working 'blind'...why would I run the risk of introducing problems into my lines that are not currently there ?

Yours is the theory ...mine is the reality....

No need to say "aaahhh" like you have somehow caught me out - rather rude tbh

Where do I say that breeders should not keep breeding?

Mine is also reality, in fact im pretty sure i have already cited quite a number of real life examples have i not?

I see this went downhill quick *sigh*

I wonder if you realise how rude you come across sometimes?

Anyway... environmental factors do have an impact on your epigenome (that's what Epigenetics is all about):

http://www.time.com/time/magazine/ar...2313-2,00.html

Perhaps I was speaking a bit too broadly in my original post.

My own personal viewpoint is that environmental factors do and can dictate matters of health where sometimes 'bad' genes can be attributed as a cause (such as cancer).

What exactly did i say that was rude?

Your first sentence. Not really in the spirit of amicable discussion imo.

Where i explained my mistake in interpreting the wording of your post? It certainly wasn't meant to sound rude - it was an explanation of why i replied asking you for information.

I think you are being rather over-sensitive, but in any case i apologise if you feel that way, it's certainly not intentional i assure you.