Recombinant DNA: Definition, Applications & Methods

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson is all about recombinant DNA, which is DNA that has been combined from multiple sources. If you ever wondered about GMO's or how scientists are manipulating DNA to cure diseases, this article is for you!

What is DNA?

DNA is the genetic material of the cell. All cells have DNA. Some cells, like the ones inside us, have a home for the DNA called the nucleus. Other cells, like bacteria, just let their DNA chill out with everything else in the cell. DNA is made of two strands of building blocks called nucleotides. There are four kinds of nucleotides, which all fit together in a unique pattern to create a gene. Genes tell the cell how to make proteins, which make up all cell structure and function. Since cells are what we and other living things are made of, the proteins give us all the traits we know and love! Some examples might be your beautiful brown eyes from our mom, or your big nose from your dad.

Below is a diagram of how DNA looks. The colored rungs are the bases and the yellow outside is the backbone of DNA, which gives it the double helix shape. The structure of DNA is important to know for changing it, which is what we do when we make recombinant DNA.


Changing the Genetic Code

Scientists have been actively working on ways to change the genetic code. They hope to help solve problems like the global food crisis, or genetic diseases. Let's look closer at how they're doing this!

First, scientists can cut and paste DNA. They snip the DNA in question apart with enzymes called restriction enzymes. These are like the scissors and the DNA is like the paper. They cut the DNA they will be modifying and then they cut the DNA they would like to add in the same way. It's like making matching puzzle pieces: the two strands of DNA must fit perfectly. We call this puzzle piece-like fit sticky ends. An example of a restriction enzyme is Eco RI, which is shown in the diagram below.

Next the scientists have to stick the DNA strands together. They use another enzymes called DNA ligase. This enzyme acts like the glue to hold the strands together. Ligase comes in and makes new bonds between the old DNA and the new DNA. We call it splicing when we glue two separate pieces of DNA together. 'Splicing' is just a fancy word for cutting and pasting DNA.


What Can We Do With the New DNA?

Now the scientists have recombinant DNA, or DNA that is spiced together from two or more different sources. There are many applications for this, so we'll look at a couple of the most important ones.

Genetically Modified Foods

Pretty much everyone has heard of GMOs at this point. GMO stands for 'genetically modified organism.' The classic example of a GMO is golden rice. This amazing plant came into play in Asia and Africa, where rice is the staple food of many communities living in poverty. These communities had many nutrient deficiencies, since they were only eating rice. The biggest problem was that they were missing beta carotene. This nutrient is important for vision, and many villagers were losing their eyesight. Scientists cut DNA that codes for this nutrient from naturally occurring sources, like carrots. They put the DNA in the rice plant's DNA and grew new genetically modified rice with the recombinant DNA. Now, the villagers could eat the new rice, which was golden in color because beta carotene is orange. This is also why carrots are orange! The villagers had a healthier diet and eye sight was restored!


Plenty of plants that you eat also are GMOs. For example, people today try to make bigger tomatoes, more resilient corn, and tastier apples. The list goes on and on.


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