Subject: Re: Copy of a gene? Was: Re: Mephisto readdressed (was Allergenicity 
	and genetic modification))
From: Oz <Oz@upthorpe.demon.co.uk>
Date: Feb 02 1997
Newsgroups: sci.bio.food-Science,sci.bio.technology

In article <5d23cp$b5c@orm.southern.co.nz>, Brian Sandle
<bsandle@southern.co.nz> writes
>Oz (Oz@upthorpe.demon.co.uk) wrote:
>: In article <5cvej1$oe3@orm.southern.co.nz>, Brian Sandle
>: <bsandle@southern.co.nz> writes
>: >J Ralph Blanchfield (jralphb@easynet.co.uk) wrote:

<assuming you can figure it all out>

>: Yes, indeed. By reproduction. However there is, you must admit, little
>: evidence of human genes in bugs that consume humans. 
>
>I was talking about protein infectious agents - prions. Prions seem very 
>important in the brain. They come from the genes. I don't know if the 
>genes are still in them. Could you explain further what you mean? And of 
>course cancer has human genes in it. So does an overactive immune system 
>destroying joints in arthritis.

You are really very confused about the situation. You really ought to
read an elementary book on genetics.

Prions are produced by normal cells in the brain. Sometimes they
misfold, and when they do enzymes in the cell are unable to break them
down. Worse, the misfolded bunches of prions collect more normal prions
and make them misfold. Personally my current best bet is that it is
nothing more complicated than a polymerisation reaction. Some genotypes
produce slightly different prions to others and these may be more, or
less resistant to the polymerisation (or whatever) and indeed some prion
types may start polymerisation readily to give natural 'genetic' CJD.
Similarly for sheep and scrapie. So yes, we all have prions in our
brains, hopefully they have not started to misfold!

Cancer is nothing more (simplifies) than a human cell type that has
mutated such that it (typically) no longer recognises the bodies
commands to stop growing. Being a human cell, the human immune system
doesn't see it as foreign, or weakly so.

>: >: 5. The separated copy gene is inserted in one of the chromosomes of
>: >: the recipient plant or animal reproductive cell, ready to be passed on
>: >: to the next generation.
>: >
>: >I am even wondering whether creatures which change their resistance to 
>: >pesticides, etc, are able to mutate their own genes by some such process. 
>: 
>: Nature provides many ways for mutations to occur. It's happening all the
>: time. Nothing odd about this.
>: 
>: <snip>
>
>So the process is quite close? But will the natural process have a better 
>regulating system which takes into account many principles of dormancy, 
>&c?

What are you talking about? I think you have a problem over what is
actually happening. You just take a gene from organism A and insert it
into organism B. The modified organism can either

1) Die, because the gene is fatal for some reason.
2) Be unable to reproduce because the gene has mucked up one of the
steps in reproduction.
3) The gene may not be expressed. In other words the gene is there, but
is not active and joins all the other inactive junk in the DNA.
4) Be incorporated in the the genome of organism B.

The only similarity with a mutation is that the new/modified gene of the
modification has to go through the same selection procedure. Usually, of
course, they die. If not, a brand new gene doing something different is
made. This could be useful, not useful, make something safer of make it
more dangerous. The only thing about natural mutations is that they are
rarely subject to stringent safety tests, or indeed any tests at all.
You are, of course, aware that most plants are filled with nasty
chemicals (even food plants) none of which would begin to pass any of
the agrochemical safety tests at all.


>Ralph said that PCR copied human genes are no safer or more dangerous than 
>naturally produced ones. I say that inserting those genes into an animal 
>may engender the following danger:
>
>Bringing the recombinant product back to a human for use might reduce the
>protection which the species barrier gives against prion disease. A
>product with a human gene in it could look to the human organism like same
>species material and and same species material can much more readily
>infect with prion disease. 

No. As far as I can understand you.

>One of the arguments for wanting to do the cystic fibrosis control factor 
>transgenic work in New Zealand was that New Zealand sheep are scrapie 
>free.

Ho, ho. You mean that scrapie has not been positively identified in
them. Remember the swiss, where they had NEVER seen scrapie because they
didn't know what it was and didn't look for it. When the did, they found
it. Given that scrapie, even in the UK, is a very rare disease that
occasionally pops uo a case in a flock, one wouldn't particularly expect
the 'no care' sheep system in NZ to pick it up. Nothing inherently wrong
in that. Bear in mind that since scrapie has been a notifiable disease
in the UK we have been blessedly free of the disease. Go figure.

> I think it was rejected on the grounds that scrapie might come here 
>from the genetic material produced in Britain. Note that because cattle and 
>sheep have more similar genetic material than sheep and humans it has 
>been thought that feeding sheep brains to cattle started the mad cow disease.
>Once started it could then be transmitted much more readily from one cow 
>to the next. It does not need a complete gene likeness to cross.

What are you on about? Scrape is NOT some transfer of genes of anything
to anything. So how can it be transferred in this way?

>And CJD an Kuru starins may not be the only prion diseases. More subtle 
>things may be happening. The Hindus do not eat cattle.

There are a whole bunch of pathological prion types, from many different
animals. They are, quite frankly, normally of no consequence, humans
have been eating animals as a major part of their diet for millions of
years. Note the spectactularly low level of prion disease in humans,
about 1:1000,000 per person year.


>Of course once you think you know, or have learnt, then you aren't so 
>receptive to the new.

Not if you are a scientist. One lives to find that what one thought one
knew, is wrong, or only part of the answer. However this doesn't mean
you grab any stupid idea going about. It had better be a better
explanation for the behaviour, and answer questions previously
unanswerable than the old. It had better not have faults and things that
don't agree with reality either.

-- 
'Oz     "Is it better to seem ignorant and learn,
         - or seem wise and stay ignorant?"