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> 1 Sep 2004 12:39:19 -0000

 

> Synthetic Genes in Food Crops

> press-release

>

>

> The Institute of Science in Society Science Society

> Sustainability http://www.i-sis.org.uk

>

> General Enquiries sam Website/Mailing

> List

> press-release ISIS Director

> m.w.ho

>

========================================================

>

>

> ISIS Press Release 01/09/04

> Synthetic Genes in Food Crops

> *********************

>

> Prof. Joe Cummins explains why genes inserted into

> GM crops

> are not " substantially equivalent " to genes in their

> native

> state

>

> A fully referenced version of this article is posted

> on ISIS

> members' website

> http://www.i-sis.org.uk/full/sgigmcFull.php.

> Details here

> http://www.i-sis.org.uk/membership.php.

>

>

> In North America, genetically modified (GM) foods

> unlabeled

> and untested are taking over the food supply. Such

> foods are

> promoted on the fiction that the foreign genes -

> usually

> taken from bacteria and viruses - inserted into GM

> crops are

> " substantially equivalent " to the natural genes.

>

> In reality, the genes used to create GM crops are

> synthetic

> approximations of the natural genes. They contain

> synthetic

> DNA sequences tuned to maximize production of

> foreign

> proteins in the plant, such as toxins killing

> insects or

> enzymes degrading herbicides, which also provide

> firm patent

> protection on the GM crop. Synthetic genes are used

> because

> the genes actively expressed in bacteria or humans

> are not

> very active in crop plants. There are several ways

> to solve

> the problem.

>

> The first is to adjust the DNA code to suit the

> 'codon bias'

> typical of the crop plant species into which genes

> from

> bacteria or mammals are introduced.

>

> The genetic code is made up of 64 three letter

> codons

> (triplets, or code words) for twenty amino acids

> plus words

> for translation start and stop. Some amino acid such

> as

> methionine (met) and tryptophan (tryp) have only one

> codon,

> while arginine (arg), leucine (leu) and serine (ser)

> each

> have six codons. The degeneracy of the code allows

> for

> alternative DNA sequences for a single protein. The

> frequencies with which different codons are used

> vary

> between groups of organisms, which is why genes from

>

> bacteria are poorly read in higher plants (and vise

> versa).

> For optimum gene expression, the code for a

> transgene often

> needs to be rewritten to achieve adequate

> performance. The

> number of possible gene sequences that can code for

> a single

> protein is staggering, it is estimated to be about

> five

> times ten to the 47th power. That number is within

> three

> orders of magnitude of the number of atoms making up

> earth

> and five times larger than the number of water

> molecules on

> earth. In synthesizing the genes used in GM crops,

> say, in

> altering a Bacillus thuringiensis (Bt) Cry toxin

> gene for

> plants, a table of plant-preferred codons is used to

>

> substitute the plant preference for the bacterial

> preference.

>

> Sometimes it is necessary to substitute one or more

> of the

> amino acids so that the final Cry toxin can function

> in the

> plant cell environment. As plant genetic engineering

> has

> " advanced " , the crucial active domains of toxins and

> enzyme

> are defined and " improved " to such an extent that

> the

> original source protein from living organisms is

> hardly

> recognizable.

>

> A third modification of the transgene is in the

> regulatory

> sequences (frequently referred to as cis elements)

> such as

> promoters, introns and transcription termination

> signals,

> which are usually taken from higher plants or their

> viral

> and bacterial pathogens. Synthetic promoters have

> also been

> created, loosely based on the cauliflower mosaic

> virus

> (CaMV) commonly used in plant genetic engineering.

> The use

> of synthetic genes in food crops has not been taken

> into

> account sufficiently in the regulatory approval of

> the food

> crops. In spite of the obvious differences between

> the

> synthetic and the natural genes from which they

> arose,

> regulators have allowed the genes and proteins

> produced in

> bacteria to be considered appropriate surrogates in

> safety

> testing for the synthetic genes and the proteins

> produced in

> food crops. This exposes the unhealthy collusion of

> corporations and their regulators.

>

> There seems to be a convenient fiction propagated by

>

> corporations, government bureaucrats and academics

> who

> depend on grant money from corporations and

> government, that

> genes from bacteria are used in producing food crops

> or that

> genes from humans are used to produced plant

> biopharmaceuticals, when, in fact, the genes used

> are

> synthetic approximations to the real things. Even

> the courts

> seem to have accepted this convenient fiction as

> fact.

>

> The next generation of GM crops is evolving towards

> a

> minimal assembly of active protein domains (domains

> are

> active area of proteins that serve as signals for

> activates

> such as toxicity or enzyme function or environment

> sensors

> for regulation) that are frequently patched together

> from a

> number of different proteins. Safety testing is

> based, once

> again, on unreal surrogates and the products are not

> labeled

> in the marketplace so that subtle changes caused by

> a few

> amino acid changes or failure to heed secondary

> protein

> modifications such as glycosylation will be

> difficult to

> trace as people are adversely affected by consuming

> the

> synthetic products in GM crops.

>

> It is imperative that the synthetic genes and their

> products

> be tested thoroughly, not only for potentially toxic

> side

> effects but for stability and recombination

> properties as

> well. These synthetic genes have not had an

> evolutionary

> history and it is a major mistake to assume that the

> genes

> can be expected to behave in all ways like the genes

> that

> they were built to represent.

>

>

>

========================================================

>

> This article can be found on the I-SIS website at

> http://www.i-sis.org.uk/

>

> If you like this original article from the Institute

> of

> Science in Society, and would like to continue

> receiving

> articles of this calibre, please consider making a

> donation

> or purchase on our website

>

> http://www.i-sis.org.uk/donations.

>

> ISIS is an independent, not-for-profit organisation

> dedicated to providing critical public information

> on

> cutting edge science, and to promoting social

> accountability

> and ecological sustainability in science.

>

> If you would prefer to receive future mailings as

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========================================================

>

> CONTACT DETAILS

>

> The Institute of Science in Society, PO Box 32097,

> London

> NW1 OXR

>

> telephone: [44 20 8643 0681] [44 20 7383 3376]

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>

> General Enquiries sam Website/Mailing

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> press-release ISIS Director

> m.w.ho

>

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