How Things Work: Genetic Engineering

Credit: Michael Setzer/SciTech Editor Credit: Michael Setzer/SciTech Editor

Since the discovery of DNA in the ’50s, scientists have been trying to understand exactly how it can influence minuscule details of a living organism. Modern techniques of genetic engineering aim to manipulate an organism’s genome in order to change biological mechanisms at the molecular level. These techniques are being applied to a variety of fields — from medicine to agriculture — and with recent breakthroughs in genetic engineering, unbelievable ideas such as cloning may not be so far-fetched.

DNA exists in the cells of all living organisms and stores information on how the cell should grow, proliferate, and interact with neighboring cells. DNA is comprised of genes, which function as recipes for how cells should build proteins. These proteins then control everything the living organism does by facilitating specific chemical reactions. This can be thought of as a “lock-and-key” mechanism of sorts: A protein with the correct shape can bind perfectly around certain molecules and force their interactions.

For example, one of the approximately 25,000 genes in a human cell contains the information on how to build the protein lactase. This protein binds to and breaks down the complex sugar lactose into relatively simple glucose, which is vital for the cell to make energy. If someone doesn’t have the gene for lactase or if the protein is not built correctly by the cell, that person will experience symptoms of lactose intolerance.

However, the protein lactase is generally only found in the cells of the digestive system. These cells have the same DNA as the cells in the brain, but the proteins found in each cell make them function differently — it would be a waste of energy for a cell to build a protein that it didn’t need.

To ensure this, DNA’s influence on (or expression of) proteins is heavily regulated within the cell. Every gene consists of a controller region that must be activated in order for that gene to be expressed into a protein. In the case of lactase, cells in the digestive system recognize that lactose is present and needs to be broken down. Only then will a specific molecule bind to a controller region for the lactase gene so that the protein-building part of the cell will receive the recipe and then protein will be made by the cell.

According to PBS, techniques of genetic engineering aim to manipulate this process of protein expression in cells to impact their functions. Scientists have the ability to introduce new genes into the genome, so that the cells produce a protein that wasn’t present before. For example, in agriculture, genetically modified fruits are forced to express specific proteins to increase their health benefits, increase growth rates, or increase their resistance to pathogens.

People who suffer from diabetes don’t have the ability to create insulin in the pancreas that allows their bodies to take glucose from their blood. With the power of genetic engineering, the gene to produce insulin was introduced into the E. coli genome so that, as these bacteria grow, they produce large amount of insulin. This can be collected and given to patients so that their bodies can then function normally.

The current hot topic of genetic research is the battle against cancer. Cancer is the unregulated growth of cells, largely due to DNA damage, where protein expression deviates from the norm and results in a pernicious attack on the body. Using a protein called nuclease, scientists can target and remove specific genes from the genome of a group of cells so that the protein won’t be made, ideally preventing the unregulated growth. The challenge is that cells have intricate levels of complexity, and simply adding and removing genes can lead to drastic effects.

Proteins play important roles in long pathways of chemical reactions; modifying these pathways must be done with caution. Still, there is a lot of hope that, by using various genetic engineering techniques, cancer can be defeated.

Techniques are also used to remove certain disease-causing genes from newborns so that they won’t suffer. It may also (at some point) be possible for parents to personalize their children by controlling the genes that express certain traits. This is where genetic engineering starts to walk the fine line of medical ethics.

Manipulating DNA allows us to change every aspect of a living organism, and the possibilities are endless. In the late ‘90s, scientists successfully took the DNA from a living sheep and used it to produce an exact clone, which they named Dolly. Since then, other animals have been cloned by scientists as they aim to learn more about the power of genetics.

The past three decades have largely been characterized by a technological revolution. Many scientists see the next few decades as defined by a genetic revolution by using the power of DNA to do everything from growing healthier foods to curing cancer.