Genetically Modified Organisms: Combining DNA from Different Sources
Because the DNA from all cells is essentially the same, scientists even combine DNA from very different sources for genetically modified organisms. Scientists have successfully put human and jellyfish genes into bacteria, and bacterial genes into crop plants.
The manipulation of a cell’s genetic material in order to change its characteristics is called genetic engineering. When a gene is inserted in a cell to help fight a disease, it’s called gene therapy.
To genetically modify organisms, scientists have to overcome many challenges:
- They need a copy of the gene they want to insert into an organism. Projects like the Human Genome Project are helping scientists identify genes and what they do. DNA sequencing allows scientists to determine the DNA codes of genes, and PCR helps them make many copies of a gene they’re interested in.
- They have to be able to insert a gene into a cell. This isn’t as easy as you might think: A DNA molecule might seem small to you, but the plasma membrane is very choosy about what it lets into cells It’s easiest to get genes into bacterial cells because they have natural processes for sharing DNA with each other. Some soil bacteria can even put their genes into crop plants, and scientists have used that to their advantage: They put a gene into these soil bacteria and then let the soil bacteria put the gene into the plant for them. Other tricks scientists have come up with include using viruses as delivery systems (viruses are pros at hijacking cells), and inventing a high-pressure gene gun that pushes DNA through barriers like skin.
- If they want to change all the cells of a multicellular organism, they have to figure out how to get a gene into all the cells. You can do this if you can introduce a gene at the very beginning of the life cycle when a multicellular organism is just a single cell. But what if you want to help a person with a genetic disease? If the person is already born, you have to figure out how to get a new gene into all of the person’s cells. The bottom line is that scientists are still working on this. In humans, some of the biggest successes have come in treating diseases involving blood cells because they can be removed, genetically engineered, and then returned to the body.
- They have to put the gene into the cell in a way that it gets used properly and doesn’t disrupt normal genes. When DNA enters a cell, the cell might mistake it for viral DNA and attempt to destroy it. Or the DNA might get added to the host DNA in a way that interferes with the code of other genes. Scientists have figured out several ways to get cells to accept genes and have recently made a huge breakthrough in being able to target genes to specific locations, but these are also areas that scientists are still working on.