What Are RNA and DNA and Are They Different?

Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA) are considered the most important molecules in cell biology. They are in charge of storing and reading genetic information that supports life.

RNA and DNA are linear polymers made up of bases, phosphates, and sugars. However, there are key differences between the two molecules. 

In this article, we’ll talk about how these molecules work together, what makes them different, and their role in our biological functions.

Why Are DNA and RNA Important?

DNA’s biological roles are vital for inheritance, protein coding, and providing instructions for life and its many processes. Meanwhile, RNA has a broader range of functions, from translating genetic information to gene activity regulation for development, cellular differentiation, and changing environments.

RNA and DNA are made up of building blocks called bases (which connect into base pairs), phosphates, and sugars. However, they're not the same, and those differences are what make them a great team in human cells.

What Are the Differences Between DNA and RNA?

A DNA strand is responsible for replicating and storing genetic information. Meanwhile, RNA is responsible for the conversion of genetic information found inside DNA to a format used for the synthesis of protein. 

Other differences include:

• Location — RNA is found in the ribosome, nucleus, and cytoplasm. A DNA strand is found in the nucleus, with small amounts in the mitochondria.
• Structure — Single-stranded molecule with shorter nucleotide chains. Double-stranded molecule B-helix with long-chain nucleotides.
• Sugar content — RNA has a more reactive sugar content (Ribose). Meanwhile, DNA’s sugar content (Deoxyribose) is less reactive.
• Bases or base pairs — RNA is made up of Adenine (A), Cytosine (C), Guanine (G), and Uracil (U). Meanwhile, DNA strands are made up of Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
• Stability — RNA is unstable in alkaline conditions, but DNA is more stable.
• Ultraviolet light sensitivity — RNA is relatively more resistant to UV damage than DNA.

DNA’s remarkable stability lets it preserve genetic information across generations, perfect for ancestry research, forensic science, and genetic health testing. If you’re curious about your genetics, check out our article on how DNA tests work for the fascinating details.

What Is Complementary Base Pairing?

Complementary base pairing describes how DNA and RNA form pairs by binding to each other. In DNA, there are four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). 

In RNA, thymine (T) is replaced by uracil (U). These bases pair together in a highly specific manner:

• Adenine (A) pairs with Thymine (T) in DNA or Uracil (U) in RNA, forming an A-T (or A-U) base pair.
• Cytosine (C) pairs with Guanine (G), forming a C-G base pair.

The complementary base pairing is essential for the processes of DNA replication and transcription.

What is Replication, Transcription, and Translation?

Your cells follow a process called the Central Dogma. Through this process, DNA makes identical copies of itself (replication) to ensure each cell receives a complete set of genetic information. 

Transcription is the process in which DNA is used as a template to create an RNA molecule, specifically messenger RNA (mRNA). Ribosomes then use mRNA instructions to assemble proteins from amino acids (translation). 

Complementary base pairing helps keep the fidelity of genetic information transfer, ensuring that the genetic code is accurately preserved during DNA replication and transcription processes. In a way, it helps prevent errors in genetic information.

What Are the Types of DNA?

DNA molecules appear as a spiral with two long strands. They are so long that they cannot fit inside the cell. 

To be able to do so, they are tightly coiled and connected at each base pair, producing chromosomes. Each chromosome has one DNA molecule. 

The different types of DNA include:

• A-DNA — Present at 75% humidity, at higher salt or ionic concentrations, or in a state of dehydration. A-DNA has the broadest helical diameter compared to other DNA forms. It is a right-handed double-helical structure that is similar to the B-DNA form. 
• B-DNA — Present at 92 % humidity and low ionic or salt concentrations. Like A-DNA, B-DNA is also a right-handed double helix. It is the most common DNA conformation.
• Z-DNA — Found in environments with very high salt concentrations. Z-DNA is a left-handed double helix that winds to the left side in a jigsaw pattern. It is thought to play a role in the regulation of genes.

What Are the Types of RNA?

RNA is considered a vital nucleotide found in all living cells, with long chains of nucleic acids. It’s a single-stranded molecule that acts as a “messenger,” forwarding instructions from DNA to control protein production.

Not all of the genes in cells are expressed into Ribonucleic acid; only some are. The types of RNA are as follows:

• Transfer RNA (tRNA) — tRNA carries the amino acids to the ribosomes. It is a free-roaming molecule that is found in the cell’s cytoplasm.
• Messenger RNA (mRNA) — mRNA encodes a polypeptide’s amino acid sequences. initially synthesized in the cell’s nucleus and then moves into the cytoplasm.
• Ribosomal RNA (rRNA) —  rRNA is responsible for ribosome protein production. Ribosomes are organelles where ribosomal proteins are made.
• Small nuclear RNA (snRNA) — snRNA forms the proteins and complexes that process RNA in eukaryotic cells.

Aside from these four, other types of RNA continue to revolutionize molecular biology as we know it. These include siRNA (small interfering RNA) and miRNA (microRNA).

Research in molecular genetics highlights how RNA’s shape-shifting ability enables critical reactions within cells.

Next Steps

Now that you understand how DNA and RNA works, feel free to explore your DNA further. Check out our comprehensive beginner’s guide to genetic testing for a deeper understanding of your own genetics.