Difference Between DNA and RNA: What Is the Difference Between DNA and RNA?

While DNA is a double-stranded molecule storing genetic information, RNA is a single-stranded molecule; it performs many different functions in regulation as well as the expression of genes.

Nucleic acids are the most important molecules in life, providing the blueprints for all cellular processes. DNA and RNA represent the two major nucleic acids. They have an extremely important function in storing and passing genetic information and in synthesizing proteins that can perform functions for a cell. If nucleic acids are present, life is thus considered possible. They thus represent the very basis of life itself for growth, development, and reproduction.

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Knowing in detail how DNA and RNA differ will bring much understanding to the inheritance and expression of genetic information. Though both are indispensable, they vary a lot in structure, function, location and stability.

Differences Between DNA and RNA

The important differences between DNA and RNA are tabulated below:

Structure and Composition of DNA and RNA

Both DNA and RNA are composed of nucleotides, which consist of a sugar molecule, a phosphate group, and a nitrogenous base. These nucleotides are linked together to form long chains.

DNA Structure

• The deoxyribonucleic acid is a polymer of deoxynucleotides.

• The pentose sugar in deoxynucleotides doesn't have the -O at C-2. Due to this fact, it is called the deoxyribose sugar.

• DNA is a polymer of nucleotides. That means many nucleotides are linked with each other via a covalent bond to form a polymer.

• The covalent bond which links the two nucleotides is known as the phosphodiester bond.

• Hence, a polynucleotide chain is formed when many nucleotides are united through the phosphodiester bond.

• DNA consists of two polynucleotide chains that are connected through hydrogen bonds.

• The two polynucleotide chains are helically arranged around each other.

• In a polynucleotide chain, the backbone is composed of sugar and phosphate while the nitrogenous bases form hydrogen bonds.

• Adenine forms two hydrogen bonds with thymine.

• Cytosine is bonded to guanine through three hydrogen bonds.

DNA diagram

DNA is the genetic material of all living organisms, except for some viruses. It stores hereditary information.

RNA Structure

• The ribonucleic acid or RNA is also a polymer of nucleotides.

• The pentose sugar of RNA has a -OH group at C-2.

• It is also a polynucleotide chain wherein the nucleotides are linked with each other via the phosphodiester bond.

• Unlike DNA, it is single-stranded and more reactive.

• RNA contains uracil as one of the pyrimidines rather than the thymine.

• RNA acts as genetic material in some viruses.

• mRNA or messenger RNA, bears the message from DNA and makes the polypeptide chain in conjunction with the ribosomes.

• rRNA or Ribosomal RNA, forms a main component of ribosomes where the mRNA binds.

• tRNA is the smallest of the three major types of RNA. It contains about 70-90 nucleotides. It carries the correct amino acid to the place of protein synthesis.

• snRNA - In eukaryotes, small nuclear RNA forms complexes with proteins for RNA processing.

RNA Diagram

The diagram below shows the structure and components of RNA.

Functions of DNA and RNA

DNA Functions

• It is the DNA that carries the specifications of everything genetic about life: development, functioning, growth, and reproduction.

• There are many such specific DNA sequences, named genes, and each one of them codes for a particular kind of protein to carry out cell functions.

• It replicates to ensure that each new cell gets an identical copy of the genetic information in the process of cell division.

• This replication is significant in that it allows inheritance to take place, whereby genetic characters are transmitted from one generation to another.

RNA Functions

• RNA plays a big role in translating the genetic information in the DNA into proteins, and does this through three types of RNA:

• mRNA (messenger RNA) returns DNA information from the nucleus to protein synthesis-containing cytoplasmic ribosomes.

• tRNA (transfer RNA) brings amino acids to the ribosomes and matches the mRNA codon with the correct amino acid.

• rRNA (ribosomal RNA) forms the core of the ribosomes, complexes in the cell where proteins are made.

• RNA molecules regulate gene expression at multiple levels that include transcriptional and post-transcriptional control.

• This gives control over the gene expressions to occur at the right time and in the right amount.

Types of DNA

Based on its location and specific function, DNA is divided into the following types:

A-DNA

• A right-handed double helix that is shorter and more compact than B-DNA.

• Dehydrated form of DNA, with 11 base pairs per turn.

• Natural occurrence is rare, but conformation is found in dehydrated samples or specific DNA-RNA hybrid structures.

B-DNA

• The most common form of DNA is with a right-handed double helix and 10 base pairs per turn.

• The normal configuration is assumed by DNA under physiological conditions. It has a wide major groove and a narrow minor groove, giving a surface architecture that is well-suited to the binding of proteins.

• It is present in most living cells under normal physiological conditions.

Z-DNA

• A left-handed double helix with an alternating sugar-phosphate backbone.

• Contains 12 base pairs per turn, and its formation is favored by some sequences and supercoiling.

• Seen in vivo, especially in GC-rich areas or under high salt.

Mitochondrial DNA (mtDNA)

• Mitochondrial chromosome

• Maternally inherited and encoded proteins with crucial mitochondrial functions

• Eukaryotic mitochondria

• The mitochondrial genome is depicted as a circle because the mitochondrial genome is a circular piece.

Chloroplast DNA (cpDNA)

• Circular DNA molecule found in chloroplasts.

• Encodes genes important for photosynthesis and other chloroplast functions.

• Found in the chloroplasts of plants and algae.

Plasmid DNA

• Small, circular DNA molecules that separate from chromosomal DNA.

• Can replicate independently and often carry genes for antibiotic resistance or other traits.

• Common in bacteria and sometimes found in archaea and eukaryotic cells.

Recombinant DNA

• DNA molecules are formed by laboratory methods of genetic recombination.

• Combines DNA from different sources into a single molecule.

• Used in genetic engineering and biotechnology.

Applications and Technological Uses

DNA Technology

• Advances in DNA technology have made it possible to alter the genetic makeup of an organism through the use of techniques like CRISPR.

• This can be applied in gene therapy and, therefore, has the potential to cure a genetic disorder through the replacement of faulty genes.

• DNA fingerprinting has also been helpful in forensic science in identifying any individual.

• This helps investigators in cases and paternity tests.

RNA Technology

• RNA interference, or turning off the expression of specific genes in organisms, permits studies of gene function as well as the production of treatments for diseases.

• This same technology has been used to develop another important class of RNA molecules: mRNA vaccines, which have proven their efficacy against COVID-19.

• Another crucial role played by RNA is that of gene expression, through which scientists are enabled to find out the way genes are regulated and expressed.