how genetic modification works

[jutntog1]

this seems like a stupid question...

basicly how do they geneticly modify animals/plants, and how does it work.=p

[zyncod]

Eighteen million different ways. The most fun way, though, has to be shooting gold particles coated with DNA at plants/animals. My only regret is that I never got to do it the *really* old-school way: with a shotgun.

[LucidDreamer]

There are a couple different ways of genetically modifying an organism. The most common way is through genetic recombination, which involves combining the DNA from two different organisms. Say for instance, you wanted a bacteria, yeast cell, or mouse to express a certain kind of gene that was normally found in a different organism.

 

1) You would first isolate the gene, using various genetics and biochemistry methodologies and procedures. You might also amplify your gene, which simply means that you make lots of the gene that you are interested in. You could do this with a method called PCR.

 

2) You would then create a vector. A vector is a virus, a circular piece of DNA called a plasmid, or a yeast chromosome that is used to transport and insert your gene of interest into the host. The host is the organism that you want to modify by changing its DNA. You accomplish this by using restriction enzymes, which cuts the vector DNA and the ends of the gene you want to express. These strands then recombine with the gene of interest inserted into the vector DNA with the help of an enzyme called ligase.

 

3) The vector is then inserted into the host's DNA. Which method you use to insert the vector into the host DNA depends on the circumstance. For instance, if you wanted a bacterial cell to express your gene's product then you could use a virus that already infects that bacterium as a vector.

 

If you wanted a mouse to express a human gene you would need to transfer your vector containing your human gene to a mouse egg cell or stem cell. You would need to use a mouse egg cell or stem cell instead of a mature cell because a) you want more than one cell to express your gene and b) its easier to insert DNA into growing cells and there are other reasons as well.

 

You can insert the DNA by using a retrovirus as a vector. You could also insert your DNA using endocytosis. Plasmids aren’t usually used to transfer DNA to mammalian cells.

 

Yeast artificial chromosomes (YAC) are also often used for mammalian recombination. YACs are useful as vectors because they are Eukaryotic, like mammalian cells. YACs are transferred into mammalian host egg cells through microinjection. The egg is then transferred into a female, which will birth the transgenic (genetically modified) animal.

[joerdz]

Does anyone know what happened to the monkey to whom glowing jellyfish genes were put into?

Last time I heard from that was from an article in january 2001

[jutntog1]

thanks for the great post lucid that was a real help

[coquina]

If you wanted a mouse to express a human gene you would need to transfer your vector containing your human gene to a mouse egg cell or stem cell. You would need to use a mouse egg cell or stem cell instead of a mature cell because a) you want more than one cell to express your gene and b) its easier to insert DNA into growing cells and there are other reasons as well.

 

The part about "you want more than one cell..." is what I have always questioned about curing genetic diseases in adults. There must be ways to make small numbers of cells affect the whole organism, or bone marrow transplants wouldn't work, but how do they do it?

[Yggdrasil]

It mostly depends on the disease, but most of the time you will want the defective gene replaced in all cells of a specific tissue type. Sometimes a small scale approach could work, but sometimes you need a systemic one.

 

For example, type I diabetes is caused by defective islet cells which cannot produce insulin. This is an example of a disease which could be cured by a small number of cells, since it affects only pancreatic islet cells. If you fix/replace enough of them to get the pancreas to produce a normal/sufficient amount of insulin, you've cured the disease.

 

On the other hand, cystic fibrosis, which results from defective sodium channels in epithilial cells (most problematic in the lungs, pancreas, and intestinal tract), requires a systemic approach. Here, replacing/fixing all of the cells would have to be the solution, since the dissease affects multiple parts of the body. Furthermore, if you just fix a few cells, you still get mucous build up because of the deffective cells you didn't fix. Even if you manage to fix/replace all of the lung cells, you still have problems with defective cells in the pancreas and intestines. It would be much more effective to fix the defective gene in the small number of cells in the embryo than it would be to fix a much larger number of cells in an adult.