David Hare-Scott > writes
>
>"Oz" > wrote in message
>> David Hare-Scott > writes

>> >I cannot see anywhere that he/she substantiates such a comparison.
>> > There is
>> >NO attempt to evaluate the risks of either technique so I cannot see how
>> >anyone can say one is more risky than the other.
>>
>> Actually that is incorrect.
>
>Sorry where are the evaluations of risk of the two techniques are the
>quantitative comparison of them?

Oh, its quite clear. Inserting a single known gene with a precise action
means you know what the effect will be (pretty much), whilst inserting a
whole bunch of genes, most of which do unknown things, clearly meas you
don;t know what the result will be.

>> >What do I think of the relative risks? As I pointed out to start of the
>> >thred with Genetic Engineering (GE) and Selective Breeding (SB) are both
>> >Genetic Modification (GM). That does not say anything about their
>relative
>> >safety. GE involves direct transfer of genetic material including that
>from
>> >totally unrelated species. SB is the alteration of the frequency of
>> >selected genes in the target population by breeding from organisms
>showing
>> >favoured characteristic(s). In GE genes are directly modified, in SB
>> >existing genes are selected in favour of others, there is no alteration
>of
>> >the genes themselves.
>>
>> Of course that's not quite right. In GE genes are not modified,
>
>Ok I didn't express this very well but it doesn't alter my point that one is
>direct manipulation of genes and the other of their frequencies in the
>population.

Not necessarily, genes from related plants can be deliberately
introduced to obtain pest or disease resistance. Many food plant
families contain highly toxic relatives with excellent disease
resistance. This is a standard technique as is using primitive varieties
from all over the world.

>And I want to know why my tomatos can't be made to taste like
>salmon too! :-)

The can, just add some smoked salmon.

>they are
>> nicked (unmodified) from elsewhere and in SE we note many garden
>> varieties (eg cereals) are so packed with mutations and polyploidy that
>> they can no longer breed unaided with wild relatives.
>>
>> >SB may select for a mutation but it does not create
>> >mutations.
>>
>> Frankly an unknown selected mutation is quite a bit more hazardous than
>> a known artificially introduced gene. Is this splendidly pest resistant
>> variety a new mutation or a good selection? Ditto nice flavour? etc etc?
>>
>> We actually don't know.
>>
>
>So what do you recommend?

We should evaluate the toxicology of food plants. This won't be as easy
as you think. In animal trials you can't usually feed high levels of a
single food for a lifetime without your stock dying or showing bad
effects. This sort of thing is well known in farming, but appears
unknown elsewhere.

>> >SB is traditional Darwinian evolution being directed by humans by
>choosing
>> >the environment. By manipulating the environment we manipulate the gene
>> >frequencies in the population much faster than otherwise and in
>directions
>> >that would never be taken without human intervention. This is where
>nearly
>> >all our cultivated plant and domesticated animal varieties came from.
>>
>> I don't think so. Most of the really useful characteristics are
>> mutations.
>
>This may be so today, I don't know what modern plant breeders get up to in
>any detail. But considering the history of edible plant breeding I would
>expect that our ancestors selected for size, flavour, etc as a primary goal.

Mostly they wanted a secure, reliable, food supply. You were far more
likely to die of starvation or hunger-related disease than worry about a
1:10,000 chance of dying from excessive intake of a plant toxin.

Which is why the NZ organic courgette growers selected the most
resistant cultivars for propogation and poisoned a whole bunch of
people.

But in fact many of the most useful characteristics (particularly
cereals) are mutations, spotted and selected.

>Most of those sorts of qualities are covered by many genes not single
>mutations, which is why takes so many generations to develop them. Does it
>really matter if such qualities are single or multi factorial? In both
>cases SB is still pushing around genotypes in populations by selecting
>phenotypes.

Hang on, why do you assume that traits, like levels of toxin production,
selected by breeders, are safe, when they can clearly be hazardous?
Known to be so, as well.

>Just consider the grossly deformed maize plant with teosinte.
>> Heck it doesn't have male and female bits of flower at the top but has
>> the female bits grotesquely poking out half way down.

No comment?

>> >Is the SB process 100% free of risk? No way. But as we are only playing
>> >with the frequency of existing genes the scope for a bad result is
>limited.
>>
>> Unfortunately not. Mutations happen. They get spotted.
>>
>> >If it wasn't people would have be getting poisoned far to often since
>> >agriculture started and neither cultivated species nor the humans that
>> >depend on them would be what they are today. The huge growth of human
>> >population could never have happened if SB was very unsafe.
>>
>> Its more that plant breeding is pretty safe. Unfortunately we don't
>> actually know if our plant species are safe because most have never been
>> tested.
>
>Hang on, we eat them all the time, isn't that a pretty large scale test?

Indeed. We also eat (and have eaten) vast tonnages of GM varieties too
for many many years with no effect.

But food plant poisoning (as I pointed out at the start) happens and is
a known hazard, particularly in some cultivars (like, say kidney beans).

>In fact feeding to animals is probably the only real test and
>> the species fed is very limited. Even so most feeds are restricted in
>> the amounts that should be fed due to animals showing negative
>> reactions. Often the precise reasons are not known but the safe feeding
>> amounts are.
>>
>> Some have been known in farming for A VeryLongTime. Not putting tupping
>> ewes on a clovery/leguminous sward is one very nice example but there
>> are others.

No comment?

>> >What about the risks of GE? To me it is an open question, one that we
>> >should put many resources into answering so we can determine the real
>risks.
>> >This needs to be done over a long period of time with plenty of redundant
>> >cross checking by different parties.
>>
>> 's OK. Massive worldwide experiment feeding to humans and livestock
>> worldwide now in its 15th year without problems.
>>
>>
>I must be ultra conservative on such issues.

How long do you need?

>I am running short of hours again so we might have to leave it until another
>day. Oz I think we have both said what we can about this interesting topic.

Hardly.

--
Oz
This post is worth absolutely nothing and is probably fallacious.

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