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Re: Stupid Question re Genetics



Hi Dale,
I will answer your queries in spite of my blood pressure.

Now you've lost me.  What do the cobs have to do with endosperm
production?  The food that is recovered consists of the kernels, the
embryo and endosperm contained in each kernel.  If 0.5% of the kernels
are transgenic, then food made from the grain is made from
approximately 0.5% transgenic grain.  Right?
answer; I hope that the determination of transgene pollution  in food is not dependent on determinations of the original grain. The reports I have seen have been based on milled grain and other processed foods. Depending on grain alone is a bad idea because a lot of transgene polluted milled or processed food can slip through. A percentage is easily measured by transgene relative to a corn nuclear gene as reference.
Corn cobs are filled with full of kernels, each kernel represents an independent fertilization so that the cob may have both transgenic and normal kernels.
The if you start with 0.5% transgenic  grains  the food may have a different percentage of transgenic pollution depending on the endosperm content of the kernels and the conditions determining endosperm level such as drought, etc. In general the milled product will have a fairly low transgene content unlike the planted transgenic corn seed that can spread pollen over a wide area and whose placement in the field and wind conditions effect the pollution of the normal crop but can lead to a significantly higher transgene pollution.
How likely is it that transgenic kernels are much bigger than
nontransgenic kernels?
answer: That remains to be seen in an experiment, I have not seen a study on endosperm content of polluting transgenic corn kernels. The fact that there is no apparent published reports on the topic does not mean that the kernels can be assumed to be "substantially equivalent". For example, Bt corn may avoid tunneling damage from insects and the damage kernels may allow for greater growth of the undamaged kernels. It is like the low seed set during drought followed by rain after seed set, the recovered kernels are few but large.
The point is that the environmental effects are not fixed and should not be assumed as if they were bureaucratic regulations.

It seems likely that food contamination with as much as 5% to 10%
transgenes could be recovered.



This may seem likely to you, but you have not offered any explanation
why this would be the case.
answer; I believe that the answer is evident. Each transgenic plant will
shed pollen effecting  fertilization of normal plants. As I have
indicated,  the spread of pollen is not fixed but efected by wind,
placement of the transgenic plant in the field , etc. A few transgenic
plants can pollinate  a large number of normal plants.

If the regulation was set as transgenes making up .5% of the mass
of the planted seeds then you would still be stuck with uncertainty
depending on the proportion of endosperm to embryo in the seeds.



You have lost me again.  The transgenes themselves constitute a
vanishingly tiny fraction of the DNA in the corn plant.  It is
pointless to try to calculate weight percentages of the transgenes
(which would be miniscule in any case).  The uncertainty regarding
endosperm-embryo ratio is unimportant, because:
1) both embryo and endosperm are transgenic in transgenic kernels
2) cornbelt dents don't vary much embryo-endosperm ratio
answer: As I pointed out it is really easy to measure the ratio of transgene to normal corn marker gene. How else could you deal with processed foods? I disagree that it is safe and reasonable to assunme that embryo to endosperm ratios are fixed, I understand that they are effected by environmental conditions and as you know endosperm is food for the embryo. Perhaps you will provide studies showing that embryo-endosperm ratios are fixed?
In conclusion, regulating transgene content in corn by % transgene polluted kernels is a bad idea because the transgenic plants can spread a lot of pollen over organic fields causing transgene pollution of the fields the year the polluted seeds were planted.
Hope I have cleared up your concerns.
Sincerely, Prof. Joe Cummins








Dale Wilson wrote:

Joe,



Getting back to Wytze's original concern , paraphrased, will a corn
crop planted at an acceptable limit, say 5 transgene polluted seeds
per thousand produce a crop of corn with 0.5% transgene pollution in
the food. The answer is; the first crop would produce 5 transgenic
plants per thousand...



I guess we agree on this after all.



but the corn crop could have  more than  50 cobs per
thousand containing transgenic grains depending on wind conditions,
placement, etc. When the food was recovered the actual percentage
transgene production in food would depend on endosperm production
mainly in the polluted cobs.



Now you've lost me.  What do the cobs have to do with endosperm
production?  The food that is recovered consists of the kernels, the
embryo and endosperm contained in each kernel.  If 0.5% of the kernels
are transgenic, then food made from the grain is made from
approximately 0.5% transgenic grain.  Right?



The percentage contamination of food would
be on a mass basis not a grain per grain basis.



How likely is it that transgenic kernels are much bigger than
nontransgenic kernels?



It seems likely that food contamination with as much as 5% to 10%
transgenes could be recovered.



This may seem likely to you, but you have not offered any explanation
why this would be the case.



If the regulation was set as transgenes making up .5% of the mass
of the planted seeds then you would still be stuck with uncertainty
depending on the proportion of endosperm to embryo in the seeds.



You have lost me again.  The transgenes themselves constitute a
vanishingly tiny fraction of the DNA in the corn plant.  It is
pointless to try to calculate weight percentages of the transgenes
(which would be miniscule in any case).  The uncertainty regarding
endosperm-embryo ratio is unimportant, because:
1) both embryo and endosperm are transgenic in transgenic kernels
2) cornbelt dents don't vary much embryo-endosperm ratio

The regulatory community expresses GMO contamination rate as a
percentage of kernels that are GMO.  This is the simplest and most
practical way to express this kind of contamination in grain.

Dale

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