Five Key Differences Between DNA and RNA

Most of you have heard of the three-letter acronyms at one point or another. Some of you may even know what they refer to. Deoxyribonucleic acid (DNA) has often been mentioned in association with the concept of being the “blueprint” for life. In some ways it is, and we will get to that in a little bit. Ribonucleic acid (RNA) is a less popular acronym than DNA as it is not in the spotlight as much, but it is just as important. While there are many similarities between the two molecules (yes, they are molecules), their differences are much more educational than their similarities as they point out much more clearly what the functions of the two molecules are.

According to the United States National Library of Medicine, every person’s DNA is made up of three billion bases. Furthermore, more than 99 percent of those bases are the same in all people. In other words, look around and notice how different we all are. Only 1% of the three billion bases is enough to make us all unique in so many ways.

These bases in a DNA sequence form genes, much like the letters in a sentence create words. Similar to how we use words to give instructions to each other, the cell uses genes as its instructions to create proteins.

But briefly, let’s talk biology and put DNA and RNA into context. The two molecules are part of one of the most important concepts in biology, namely the central dogma that refers to the process of DNA being made into RNA that is made into protein. Let’s back up a little bit. So, earlier when we mentioned that DNA is the blueprint for life, the central dogma points to exactly that, how we are made. DNA, located deep within the cell in its nucleus, is turned into RNA during a process that is called transcription. This RNA, by virtue of being a copy of the DNA, is then translated into all the proteins that make us who we are and keep us alive. This central dogma already points to two essential differences between DNA and RNA:

1. DNA is transcribed to RNA

DNA is vital (pun intended) for cells to multiply and for organisms to develop. DNA contains all of the genes that make an organism into what they are. As such, DNA is precious and must be protected. It is located within the nucleus that it never leaves. Rather, during transcription, copies of DNA are made in the form of RNA that goes on and codes for all of the important things. The difference between the two molecules is that the process of transcription only goes one way, namely DNA is made into RNA, and never the other way around.

2. RNA is translated to proteins

RNA is translated to proteins

So, given the aforementioned, RNA is a copy of DNA and ready to be turned to proteins. This process is called translation, and it happens in ribosomes, or little processing units that read the RNA’s building blocks, the nucleotides. Every three nucleotides code for an amino acid in a string of amino acids that make up a protein. Only RNA can be translated into proteins, not DNA.

Given these two differences, you already know a lot about the two molecules. One similarity between the two is that both are long-stranded molecules or long chains of letters that are important building blocks for everything that comes after, namely nucleotides. There are four of them, which brings us to the next difference between the two molecules.

3. Nucleotide sequence

While the DNA molecule is made up of the four nucleotides, namely Cytosine, Guanine, Adenine andThymine. Each nucleotide is made up of a phosphate group, a sugar group and a nitrogen base. The RNA molecule is also a string of four nucleotides, namely Cytosine, Guanine, Adenine andUracil.

4. One strand, two strands

DNA is a double stranded molecule. As the term implies, it has two strands or sugar backbones. RNA, on the other hand, is made up of just one strand of nucleotides. DNA’s double helix—the two strands—is held together by molecular bonds between the nucleotides, whereby cytosine binds to guanine and adenine binds to thymine (or uracil in RNA).

Now you know almost everything there is to know about DNA and RNA and how the two are different. However, things are never as simple as they seem, and this is particularly true for molecular biology and genetics. Just when you think that you have understood everything there is, you will quickly realize that there is, in fact, more. Remember how we began with the intent to cover the five differences between DNA and RNA? There is a fifth, more complicated difference between the two molecules, and this difference highlights the more nuanced details of translation.

5. Different types of RNA molecules

There are several different RNA molecule models, depending on the function of the RNA molecule. These include biologically active RNAs, such as mRNA, tRNA and rRNA. The first, namely mRNA, refers to messenger RNA that, as the name implies, carry DNA information from the nucleus to the ribosome. Furthermore, tRNA refers to transfer RNA that is important in the recognition of the three letter code, or the codon, that codes for a specific amino acid. Ribosomal RNA, or rRNA, is at the heart of the ribosomal machinery that manufactures proteins by virtue of stringing together amino acids.

Now that you know just a little bit more about DNA and RNA, rest assured that there are even more differences between the two molecules. They highlight not only how advanced our understanding of molecular biology has become, but also just how precise and elegant mother nature is in the processes that are so important in life.

Laura Day