Difference between DNA and RNA

Life on Earth displays an immense variety, ranging from single-celled protozoans to intricate multicellular plants and animals. However, at the molecular level, all life shares a fundamental similarity, being composed of the same essential building blocks – DNA and RNA. One key distinction between DNA and RNA is that DNA is double-stranded, while RNA is single-stranded.

Read further to delve into the detailed differences between DNA and RNA.

Following are the important differences between DNA and RNA:

Within cells, DNA (Deoxyribonucleic acid) serves as the nucleic acid blueprint for synthesizing proteins. DNA comprises the sugar deoxyribose, phosphates, and a distinct sequence of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).

The DNA molecules contain the instructions necessary for a living organism’s growth, development, and reproduction. These instructions are housed within each cell and are passed down from parents to offspring.

Composed of nucleotides, which consist of a nitrogenous group, a phosphate group, and a sugar group, DNA’s genetic code is determined by the sequence of nitrogenous bases: thymine (T), guanine (G), cytosine (C), and adenine (A).

Genes are formed by the arrangement of these nitrogenous bases within DNA, which is crucial for protein synthesis. RNA, another nucleic acid, translates this genetic information into proteins from DNA.

The nucleotides join together to form two long strands that twist around each other, creating a structure known as the double helix, reminiscent of a ladder. In this structure, the sugar and phosphate molecules make up the sides, while the bases form the rungs.

The bases on one strand pair up specifically with bases on the other strand: guanine with cytosine, and adenine with thymine.

Due to their extreme length, DNA molecules must be tightly packaged to fit inside cells. They are coiled tightly to form structures called chromosomes. Each chromosome contains a single DNA molecule. In humans, there are 23 pairs of chromosomes found within the nucleus of cells.

Main article: DNA Structure

• A-DNA: Under conditions of 75% relative humidity or in environments with higher salt concentrations such as K+, Na+, Cs+, or during dehydration, A-DNA maintains a structure with 11 nucleotide pairs per helical turn, rising 2.56Å vertically per base pair. It possesses the widest helical diameter among all DNA forms, measuring 23Å. A-DNA is a right-handed helix with a rotation of 32.70° per base pair.

• B-DNA: The most prevalent form, found in the majority of DNA under neutral pH and physiological salt concentrations, is the B-form. It features 10 base pairs per helical turn, with a helical diameter of 20Å and a vertical rise of 3.4Å per base pair. The Watson-Crick double helix model defines the B-form of DNA.

• C-DNA: Observed at a relative humidity of 66% and in the presence of select ions such as Lithium (Li+), C-DNA typically exhibits around 9.33 base pairs per turn. It has a helical diameter of approximately 19Å, with a vertical rise of 3.320Å per base pair in the right-handed helix.

• D-DNA: Rarely observed, D-DNA is an extreme variant characterized by its negative tilt of 8 base pairs from the helix axis, with an axial rise of about 3.03Å.

• Z-DNA: Found in environments with very high salt concentrations, Z-DNA is a unique left-handed helical structure. Its backbone forms a zig-zag pattern due to the sugar-phosphate linkage, where the recurrent monomer is the dinucleotide, as opposed to the mononucleotide observed in other DNA forms.

RNA, or Ribonucleic Acid, is a nucleic acid that plays a crucial role in protein synthesis. It serves as a messenger, carrying instructions from DNA to control the synthesis of proteins in all living cells.

Composed of long chains of nucleic acids, RNA consists of the sugar ribose, phosphates, and four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and uracil (U). While DNA and RNA share the nitrogenous bases A, G, and C, thymine (T) is typically exclusive to DNA, whereas uracil (U) is specific to RNA.

Types Of RNA

Some genes in cells are transcribed into RNA. Here are the different types of RNA, each encoded by specific genes:

• tRNA – Transfer RNA, known as tRNA, transports amino acids to ribosomes during translation.
• mRNA – Messenger RNA, or mRNA, carries the genetic information for encoding amino acid sequences of a polypeptide.
• rRNA – Ribosomal RNA, or rRNA, combines with ribosomal proteins to form ribosomes, the organelles responsible for translating mRNA.
• snRNA – Small nuclear RNA, or snRNA, forms complexes with proteins used in RNA processing in eukaryotic cells.

Explore More: Structure of RNA

In the context of cellular function, it’s important to note that some proteins act as enzymes, facilitating cellular processes by catalyzing chemical reactions. These reactions occur when the enzyme binds to its substrate at the active site, a region of the enzyme that matches the substrate in size, shape, and chemical properties.

The specific size, shape, and chemical properties of an enzyme’s active site are determined by the arrangement of its amino acids, the building blocks of the protein. For a cell to effectively produce an enzyme, it must have precise control over the arrangement of amino acids during the synthesis of proteins.

Proteins are crucial for a cell’s ability to thrive and adapt to its environment. They are used by cells to maintain their structure and to speed up vital chemical reactions such as photosynthesis and respiration.

Without the reliable production of necessary proteins, a cell’s survival is compromised, highlighting the critical role that proteins play in cellular life processes.

More to Read: Proteins

Further Reading

• The Polynucleotide Molecule
• Difference Between Gene and DNA