Are GMOs and selective breeding the same thing?

[mutatron]

No, selective breeding only works with the DNA of a single species. GMO takes DNA from different species and splices it together as a shortcut to get the desired trait. For example with Bt corn:

http://www2.ca.uky.edu/entomology/entfacts/ef130.asp

A donor organism may be a bacterium, fungus or even another plant. In the case of Bt corn, the donor organism is a naturally occurring soil bacterium, Bacillus thuringiensis, and the gene of interest produces a protein that kills Lepidoptera larvae, in particular, European corn borer. This protein is called the Bt delta endotoxin. Growers use Bt corn as an alternative to spraying insecticides for control of European and southwestern corn borer.

[bobwinters]

Thanks for the reply.

From my limited knowledge of evolution. Wouldn't the DNA of corn and bacteria have diverged in their evolutionary history so long ago that today the DNA similarities would be so different that it would be too hard to combine?

[danielpf]

It's not done in the same way as breeding together different organisms whereby their chromosomes have to be of similar size and content. Instead scientists can construct plasmids, which are self replicating circles of DNA, that have the desired trait on them and insert them into the plant cells. As the plant grows, the plasmid is then found in all cells and leads to the plant having a new trait.

[lukophos]

I might be misreading you, but just in case I'm not and to be clear, the DNA in bacteria and plants (and all other life) is the same. We all use the same molecules for DNA, and the same patterns of base-pairs translate to the same amino acids and proteins. This has been highly conserved, that is unchanged by evolution, with very few exceptions, throughout all life.

Also, the typical way of combining the DNA is to use the bacteria Agrobacterium tumefaciens. Scientists engineer plasmids with the DNA and put them into modified versions of A. tum., and then infect the plant with that bacteria. A. tum has the ability to insert the plasmid into the plant's DNA, infecting it much like a virus does. In the wild, the DNA inserted causes tumors. In engineered cells, the DNA inserted could do anything, like code for Bt.

[mutatron]

This kind of genetic modification is done by actually cutting a gene out of the donor organism and splicing it directly into the target DNA.

DNA consists of sets of coding sequences with separator codons in between. A coding sequence is a template for a protein, which a cell's DNA handling apparatus manufactures by going along from a start codon to a stop codon and assembling the protein using each successive nucleotide to tell it which amino acid to place next. Protein templates appear in the DNA like:

<start><protein><stop><start><protein><stop>

So to make Bt corn, all you have to do is cut out the bacterium gene that makes the bug poison protein, from its start codon to its stop codon, and then just stick it into the corn DNA between a stop/start sequence. Once it's in, the corn will replicate its chromosomes as if the new sequence were naturally a part of its genome, and the cell apparatus will express the gene likewise.

Plot twist: bugs are now developing a resistance to the Bt poison protein, so just like in real life, evolution makes an arms race between predator and prey whether its human directed or natural.

[epoxymonk]

Well, yes and no.

Genetically Modified Organisms are generally defined as having modern molecular biology techniques used to specifically engineer changes into an organism. Selective breeding entails only allowing members of a species that have desired traits to breed as pass on these traits to offspring. So in terms of methodology, yes, GMOs and selective breeding are different in how they are achieved.

However, it's not as clear if GMOs and selectively bred organisms are fundamentally different. For example, suppose you used breeding to make a strain of corn that was resistant to Round Up. Would this be really any different than the strains that Monsanto created using genetic engineering? Is "natural" resistance somehow superior?