DNA vs RNA

Diffen › Science › Biology › Microbiology

DNA, or deoxyribonucleic acid, is like a blueprint of biological guidelines that a living organism must follow to exist and remain functional. RNA, or ribonucleic acid, helps carry out this blueprint's guidelines. Of the two, RNA is more versatile than DNA, capable of performing numerous, diverse tasks in an organism, but DNA is more stable and holds more complex information for longer periods of time.

Comparison chart

DNA versus RNA comparison chart
	DNA	RNA
Stands For	DeoxyriboNucleic Acid	RiboNucleic Acid
Definition	A nucleic acid that contains the genetic instructions used in the development and functioning of all modern living organisms. DNA is the primary hereditary material that stores the complete genetic blueprint for an organism.	A versatile nucleic acid that plays multiple roles in coding, decoding, regulation, and expression of genes. RNA acts as the intermediary between genetic information and functional proteins, while also performing catalytic and regulatory functions.
Primary Function	Long-term storage and transmission of genetic information across generations. Serves as the master blueprint for all cellular functions and organismal characteristics.	Transfers genetic info from DNA to ribosomes (mRNA), decodes instructions (tRNA), forms ribosome catalytic core (rRNA), regulates gene expression (miRNA, siRNA, lncRNA).
Structure	Double-stranded helix with antiparallel strands. Sugar-phosphate backbone with nitrogenous bases. Strands held by hydrogen bonds between complementary base pairs.	Usually single-stranded but folds into complex 3D structures (hairpins, loops, pseudoknots). Structural versatility enables catalytic and regulatory functions.
Sugar Component	2-deoxyribose (lacks hydroxyl group at 2' carbon). Absence of 2'-OH group makes it more chemically stable.	Ribose (has hydroxyl group at 2' carbon). The 2'-OH group makes RNA more reactive but enables catalytic activity.
Nitrogenous Bases	Adenine (A), Thymine (T), Cytosine (C), Guanine (G). Purines: A and G. Pyrimidines: T and C.	Adenine (A), Uracil (U), Cytosine (C), Guanine (G). Purines: A and G. Pyrimidines: U and C. Uracil replaces thymine, lacks a methyl group.
Base Pairing Rules	A pairs with T via 2 H-bonds; C pairs with G via 3 H-bonds. Complementary base pairing enables accurate replication and repair.	In double-stranded regions: A pairs with U via 2 H-bonds; C pairs with G via 3 H-bonds. Can also form non-Watson-Crick base pairs in complex structures.
Helix Geometry	B-form helix (most common): right-handed, ~10.5 bp/turn, 2 nm diameter, major/minor grooves. Can also form A-form and Z-form (left-handed).	A-form helix: right-handed, ~11 bp/turn, wider and shorter than B-form, deeper major groove. More compact and stable for single strands forming local double-stranded regions.
Types and Variants	Nuclear DNA (chromosomal), mitochondrial DNA (mtDNA, circular, maternally inherited), chloroplast DNA (cpDNA in plants, circular), plasmids in bacteria.	mRNA, tRNA, rRNA, miRNA, siRNA, lncRNA, snRNA, piRNA, circRNA.
Cellular Location	Primarily in nucleus (chromatin with histones). Also in mitochondria and chloroplasts (plants) as circular, histone-free molecules.	Synthesized in nucleus, transported to cytoplasm. Found in cytoplasm, ribosomes, nucleus, and various compartments depending on RNA type and function.
Molecular Size	Extremely large. Human genome: ~3.2 billion bp/haploid set. Chromosomes: 50-250 million bp. Mitochondrial DNA: ~16,500 bp.	Much smaller than genomic DNA. mRNA: hundreds to tens of thousands of nucleotides. tRNA: 76-90 nt. rRNA: ~120 nt (5S) to ~5,000 nt (28S). miRNA: 21-23 nt.
Stability	Highly stable: deoxyribose lacks reactive 2'-OH, double-strand protects bases, smaller grooves limit enzyme access. Stable in alkaline. Can persist thousands of years (ancient DNA).	Less stable: 2'-OH causes base-catalyzed hydrolysis, single-strand exposes bases, wider grooves allow RNase access. Unstable in alkaline. Instability allows rapid cellular response.
Chemical Reactivity	Low reactivity. Absence of 2'-OH prevents nucleophilic attack and self-cleavage. Ideal for long-term stable information storage.	Higher reactivity. 2'-OH acts as nucleophile, attacking phosphodiester bond, causing self-cleavage. Enables ribozyme catalysis but requires continuous synthesis.
Lifespan in Cells	Permanent in living cells (except cell death). Persists entire organism lifespan. In dead organisms, survives extended periods depending on conditions.	Temporary and dynamic. Continuously synthesized, used, degraded. Half-life: minutes (some mRNAs) to days (rRNA in non-dividing cells). Rapid turnover enables quick cellular adjustment.
Replication/Synthesis	Self-replicates via DNA polymerase. Needs RNA primers (can't start de novo). Semiconservative replication. Extensive proofreading: ~1 error per 10 billion bases.	Synthesized from DNA via RNA polymerase. Can initiate de novo (no primers needed). Not self-replicating except RNA viruses. Lower fidelity: ~1 error per 10,000-100,000 bases.
Catalytic Activity	No natural catalytic activity. Functions only as information storage. Artificial DNAzymes created in labs for research.	Many RNAs are catalytic (ribozymes). Examples: ribosomal peptidyl transferase, self-splicing introns, RNase P. Dual role as info carrier and catalyst supports RNA World hypothesis.
Damage and Repair	Damage from UV (thymine dimers), radiation, oxidation, alkylation. Extensive repair mechanisms: base/nucleotide excision, mismatch repair, double-strand break repair. Thymine (vs uracil) detects cytosine deamination.	More resistant to UV thymine dimers (uses uracil). Susceptible to oxidation and hydrolysis. Damaged RNA degraded and replaced, not repaired. Uracil vs thymine is metabolically efficient since RNA is disposable.
Modifications	Modified post-synthesis via methylation. Cytosine methylation (5-mC) regulates gene expression, crucial for epigenetic inheritance. Modifications don't change sequence but affect gene expression.	170+ post-transcriptional modifications: pseudouridine, m6A, m5C, inosine, others. Regulate stability, localization, translation efficiency. Modified nucleosides in tRNA essential for codon recognition.
Evolutionary Origin	Evolved after RNA as more stable storage molecule. Transition from RNA to DNA genomes separated information storage (DNA) from catalysis/transfer (RNA/proteins).	RNA World hypothesis: RNA predated DNA and proteins, serving as genetic material and catalyst. Supported by RNA catalysis, ribosome role, RNA nucleotides as DNA precursors. Some viruses still use RNA genomes.
Modern Applications	Genetic testing, forensics (fingerprinting), ancestry/paternity, sequencing (human genome), gene therapy, CRISPR editing, synthetic biology, data storage, personalized medicine, GMO crops, DNA vaccines.	mRNA vaccines (COVID-19), RNAi therapeutics (siRNA drugs like patisiran), antisense oligonucleotides, CRISPR guide RNAs, RNA aptamers, RNA-seq, single-cell sequencing.
Key Biological Significance	Universal genetic material in cellular life. Stability preserves and transmits genetic info across generations. Mutations provide evolution raw material. Revolutionized medicine, forensics, biotech.	Bridges genetic info and functional proteins (Central Dogma: DNA→RNA→Protein). Regulates nearly all gene expression. Discovery of catalytic/regulatory RNAs transformed understanding of regulation and life origins.

Structure

DNA and RNA are nucleic acids. Nucleic acids are long biological macromolecules that consist of smaller molecules called nucleotides. In DNA and RNA, these nucleotides contain four nucleobases — sometimes called nitrogenous bases or simply bases — two purine and pyrimidine bases each.

Structural differences between DNA and RNA.

DNA is found in the nucleus of a cell (nuclear DNA) and in mitochondria (mitochondrial DNA). It has two nucleotide strands which consist of its phosphate group, five-carbon sugar (the stable 2-deoxyribose), and four nitrogen-containing nucleobases: adenine, thymine, cytosine, and guanine.

During transcription, RNA, a single-stranded, linear molecule, is formed. It is complementary to DNA, helping to carry out the tasks that DNA lists for it to do. Like DNA, RNA is composed of its phosphate group, five-carbon sugar (the less stable ribose), and four nitrogen-containing nucleobases: adenine, uracil (not thymine), guanine, and cytosine.

RNA folding in on itself into a hairpin loop.

In both molecules, the nucleobases are attached to their sugar-phosphate backbone. Each nucleobase on a nucleotide strand of DNA attaches to its partner nucleobase on a second strand: adenine links to thymine, and cytosine links to guanine. This linking causes DNA's two strands to twist and wind around each other, forming a variety of shapes, such as the famous double helix (DNA's "relaxed" form), circles, and supercoils.

In RNA, adenine and uracil (not thymine) link together, while cytosine still links to guanine. As a single stranded molecule, RNA folds in on itself to link up its nucleobases, though not all become partnered. These subsequent three-dimensional shapes, the most common of which is the hairpin loop, help determine what role the RNA molecule is to play — as messenger RNA (mRNA), transfer RNA (tRNA), or ribosomal RNA (rRNA).

Function

DNA provides living organisms with guidelines—genetic information in chromosomal DNA—that help determine the nature of an organism's biology, how it will look and function, based on information passed down from former generations through reproduction. The slow, steady changes found in DNA over time, known as mutations, which can be destructive, neutral, or beneficial to an organism, are at the core of the theory of evolution.

Genes are found in small segments of long DNA strands; humans have around 19,000 genes. The detailed instructions found in genes—determined by how nucleobases in DNA are ordered—are responsible for both the big and small differences between different living organisms and even among similar living organisms. The genetic information in DNA is what makes plants look like plants, dogs look like dogs, and humans look like humans; it is also what prevents different species from producing offspring (their DNA will not match up to form new, healthy life). Genetic DNA is what causes some people to have curly, black hair and others to have straight, blond hair, and what makes identical twins look so similar. (See also Genotype vs Phenotype.)

RNA has several different functions that, though all interconnected, vary slightly depending on the type. There are three main types of RNA:

Messenger RNA (mRNA) transcribes genetic information from the DNA found in a cell's nucleus, and then carries this information to the cell's cytoplasm and ribosome.

Transfer RNA (tRNA) is found in a cell's cytoplasm and is closely related to mRNA as its helper. tRNA literally transfers amino acids, the core components of proteins, to the mRNA in a ribosome.

Ribosomal RNA (rRNA) is found in a cell's cytoplasm. In the ribosome, it takes mRNA and tRNA and translates the information they provide. From this information, it "learns" whether it should create, or synthesize, a polypeptide or protein.

DNA's genes are expressed, or manifested, through the proteins that its nucleotides produce with the help of RNA. Traits (phenotypes) come from which proteins are made and which are switched on or off. The information found in DNA determines which traits are to be created, activated, or deactivated, while the various forms of RNA do the work.

One hypothesis suggests that RNA existed before DNA and that DNA was a mutation of RNA. The video below discusses this hypothesis in greater depth.