GM Food Animals coming

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GM Food Animals coming

Wed, 15 Nov 2006 23:27:03 +0000 (GMT)

 

 

 

 

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ISIS Press Release 15/11/06

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GM Food Animals Coming

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Foods derived from genetically modified animals are likely

to be contaminated by potent vaccines, immune regulators,

and growth hormones, as well as nucleic acids, viruses, and

bacteria that have the potential to create pathogens and to

trigger cancer

 

Prof. Joe Cummins and Dr. Mae-Wan Ho

 

Heritable versus non-heritable modifications

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The Codex Alimentarius Commission of the United Nations is

preparing guidelines for safety assessment of foods derived

from recombinant-DNA animals [1], which is a sure sign that

GM animal food is coming to our table.

 

Codex distinguishes between heritable and non-heritable

genetic modification of food animals. Heritable genetic

modification involves genetic changes that persist in sperm

and egg while non-heritable modification involves the

introduction of modified genes such as vaccines into the

somatic tissue of animals. Codex asks: " Are there specific

food safety questions (e.g. with regard to types of vectors)

that should be considered relative to the assessment of

safety of food from animals containing heritable versus non-

heritable traits? "

 

We present an overview of heritable and non-heritable

modifications, which are not as distinct as Codex thinks,

and point to risks that have not been seriously considered.

This article is base on a report we submitted to Codex [2],

Genetically Modified Food Animals Coming , which contains

all the detailed references.

 

Heritable modifications

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Heritable alteration or genetic modification (GM) of food

animals has been achieved since the early 1980s, mostly by

injecting naked DNA. Between 1 and 20 million copies of the

transgene (gene to be integrated into the animal genome) are

injected into the embryo pronucleus (the nucleus before

fertilization) or into the egg cytoplasm, with at most about

one percent of injected embryos becoming transgenic animals.

The transgenes integrate randomly, though rare instances of

homologous recombination with host genes may occur.

 

A number of different vectors have been used to deliver

transgenes in animals. Transposons (mobile genetic units

capable of transferring genes) are not widely used in

vertebrates. Lentivirus (lenti-, Latin for " slow " ), a genus

of slow viruses of the Retroviridae family characterized by

a long incubation period, can deliver a significant amount

of genetic information into the DNA of the host cell, and

are among the most efficient gene delivery vectors. HIV

(human immunodeficiency virus), SIV (simian immunodeficiency

virus), and FIV (feline immunodeficiency virus) are all

examples of lentiviruses that have been used successfully

with farm animals such as chicken, pig and cow. They are

about 50 times more efficient than DNA injection at

producing transgenic animals. One problem encountered is

that the long terminal repeats of the integration vector

interfere with the inserted gene's promoter. Homologous

recombination has been used to produce specific gene " knock

outs " by replacing an active gene with an inactive one.

" Knock in " refers to the integration of a foreign gene at a

specific target, disrupting the target gene by inserting the

transgene.

 

Transgenes are designed according to rules that result in

gene expression in the host animal, such as the presence of

at least one intron, exclusion of GC rich regions,

particularly CpG rich motifs. Gene sequences called

insulators are often included; these contain transcription

enhancers and enhancer blockers to avoid cross talk with

adjacent genes, and chromosome openers that modify histones

to allow the transcription machinery to be expressed.

Finally, RNAi may be used to inactivate specific genes

either as heritable transgenes or as non-heritable gene

treatments. A vector based on HIV dramatically increased the

efficiency of producing transgenic animals, thereby greatly

reducing cost. Foetal fibroblast cells can be modified and

then cloned to produce transgenic animals.

 

A novel approach was to transfect germ cell tissue in

neonatal testis by electroporation, which was then grafted

onto the backs of nude mice (nude mice are immune deficient

and tolerate grafts from mammalian tissues). The nude mice,

previously castrated, produced mature transgenic sperm that

functioned well in in vitro fertilization to produce

transgenic farm animals. The technique has been used

successfully in cattle, pigs and even humans (though without

producing an actual human as yet). The technique is promoted

for humans as a means of allowing men requiring irradiation

cancer treatment to set aside viable sperm for in vitro

fertilization .

 

Read the rest of this article here

http://www.i-sis.org.uk/GM-Food-Animals.php

 

 

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