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RNA vs. DNA

Updated on September 28, 2021
Written by
Emjay B
6 sources cited
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In cell biology, Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA) are considered the most important molecules. They are in charge of storing and reading genetic information that supports life.

RNA and DNA are linear polymers. They’re made up of bases, phosphates, and sugars. However, there are key differences between the two molecules. These dissimilarities enable RNA and DNA to work together while fulfilling their all-important roles.

Both DNA and RNA play important roles in biological functions

There is a wide range of RNA functions — from the translation of genetic information to gene activity regulation for development, cellular differentiation, and changing environments.

DNA’s biological roles are vital for inheritance, protein-coding, and the provision of instruction for life and its many processes.

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The Differences Between RNA and DNA

Here, we compare RNA vs. DNA, looking at their key differences in terms of function, location, structure, sugar content, bases, stability, and sensitivity to ultraviolet light.

Ribonucleic Acid (RNA)Deoxyribonucleic Acid (DNA)
Function
It is responsible for the conversion of genetic information found inside DNA to a format used for protein-building. It is then moved to ribosomal protein factories.It is responsible for replicating and storing genetic information. DNA is considered the blueprint for all of the genetic information found inside an organism.
Location
Found in the ribosome, nucleus, and cytoplasmFound in the nucleus, with small amounts in the mitochondria
Structure
Single-stranded molecule A-helix with shorter nucleotide chainsDouble-stranded molecule B-helix with long-chain nucleotides
Sugar Content
RiboseDeoxyribose
Bases
Adenine (A), Cytosine (C), Guanine (G), and Uracil (U)Adenine (A), Cytosine (C), Guanine (G), and Thymine (T)
Stability
Unstable in alkaline conditionsMore stable than RNA
Sensitivity to Ultraviolet (UV) Light
Relatively resistant to UV damage compared to DNAVulnerable to UV damage

What is DNA?

DNA, or Deoxyribonucleic acid, is the nucleic acid in cells which is the original blueprint for protein synthesis. DNA contains phosphates, deoxyribose sugar, and a unique sequence of the following nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). 

DNA molecules hold the instructions needed by a living organism to develop, grow, and reproduce. Instructions are found inside every cell and are passed on from generation to generation.

DNA is composed of nucleotides containing a phosphate group, a nitrogenous group, and a sugar group. In determining the genetic code, the order of the nitrogenous bases Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) is very important. 

The human genome is composed of approximately 3 billion DNA base pairs.

The base pairing is as follows: Adenine and Thymine, Guanine and Cytosine.

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, producing chromosomes. Each chromosome has one DNA molecule. In humans, 23 pairs of chromosomes are present inside the cell’s nucleus.

Aside from storing genetic information as one of its primary functions, DNA also plays a part in:

  • Cellular metabolism
  • DNA Fingerprinting
  • Gene Therapy
  • Mutation
  • Replication process

The Types of DNA

  • A-DNA: This is 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: This is present at 9.25% 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: This is 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 is RNA?

RNA, or Ribonucleic acid, is the nucleic acid that plays a direct role in the synthesis of proteins. RNA is considered an important nucleotide found in all living cells, with long chains of nucleic acids. It acts as a “messenger,” forwarding instructions from DNA to control protein synthesis.

RNA molecules contain phosphates and sugar ribose. Just like DNA, it also has nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Uracil (U). Take note that in DNA, Uracil (U) is replaced by Thymine (T).

RNA plays three roles in protein synthesis: as a messenger, for transfer, and in ribosome production. These roles are reflected in the different types of RNA.

Types of RNA

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

  • tRNA: Also known as “transfer” RNA, tRNA carries the amino acids to the ribosomes. It is a free-roaming molecule that is found in the cell’s cytoplasm.
  • mRNA: Also known as “messenger” RNA, the mRNA encodes a polypeptide’s amino acid sequences. It is found in the cell’s nucleus.
  • rRNA: Also known as “ribosomal” RNA, rRNA is responsible for ribosome protein production. Ribosomes are organelles where ribosomal proteins are made.
  • snRNA: Also known as “small nuclear” RNA, snRNA forms the proteins and complexes used to process RNA in eukaryotic cells.

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

Commonly Asked Questions on DNA and RNA

What are RNA and DNA composed of?

RNA and DNA are nearly identical nucleotide polymers. They have the same three base pairs, except for Thymine (T) and Uracil (U). Thymine is found in DNA, while Uracil substitutes Thymine in RNA. 

Where are RNA and DNA found?

RNA is found in the following sites: nucleus, cytoplasm, and ribosomes. Meanwhile, DNA is located in the mitochondria and nucleus of the cell. 

How does RNA and DNA propagate?

While DNA is able to self-replicate, RNA cannot. RNA is synthesized into DNA as needed.

Which is the better genetic material?

DNA is more stable because its deoxyribose sugar has one less oxygen-containing hydroxyl group. On the other hand, RNA has ribose sugar and is more reactive compared to DNA. Thus, DNA is considered a better genetic material than RNA.

Are there similarities between RNA and DNA?

Yes. RNA and DNA have three similar nitrogenous bases: Cytosine (C), Adenine (A), and Guanine. They also have phosphate backbones where the bases are attached.

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Resources

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"The 99 percent... of the Human Genome." Science in the News. The Graduate School of Arts and Sciences, Harvard University. 1 Oct 2012.

"What is RNA." RNA Society.

"DNA and RNA." Jefferson Computational Medicine Center.

Lodish H, Berk A, Zipursky SL, et al. “The Three Roles of RNA in Protein Synthesis.” Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000. Section 4.4.

Mandal, A. "DNA Biological Functions." News Medical Life Sciences.

"Role of RNA in Biology." RNA Therapeutics Institute, UMass Chan Medical School.

Emjay B
Content Contributor
Emjay is a content writer for Know Your DNA. As a Physical Therapist and a registered nurse, she has extensive medical knowledge and hands-on experience in patient care. After getting her nursing license, she pursued full-time writing focused on healthcare.
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