DNA and RNA Structure

DNA, or deoxyribonucleic acid, is a molecule composed of two long chains of nucleotides that coil around each other to form a double helix.
Each nucleotide in a DNA molecule is made up of a deoxyribose sugar, a phosphate group, and one of the four nitrogenous bases: adenine (A), cytosine (C), guanine (G), or thymine (T).
Adenine pairs with Thymine and Guanine pairs with Cytosine through hydrogen bonds to form the DNA double helix.
DNA is the genetic material that carries information about an organism and is used to pass traits from parent to offspring.

RNA, or ribonucleic acid, is mostly composed of a single strand of nucleotides and uses the same bases as DNA, except it replaces thymine with uracil (U).
Each nucleotide in an RNA molecule is made up of a ribose sugar, a phosphate group, and one of the four nitrogenous bases: adenine (A), cytosine (C), guanine (G), or uracil (U).
RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, playing a critical role in protein synthesis and sometimes catalysing biological reactions.

Gene expression starts with DNA at the core of the cell. When a certain gene needs to be used, the DNA unwinds and acts as a template for the production of an RNA molecule, in a process known as transcription.
The RNA, now containing the complementary sequence to the original DNA strand, leaves the nucleus and goes into the cytoplasm, where it will play a central role in the production of proteins.
In the cytoplasm, the RNA molecule is decoded to produce a chain of amino acids which combine to form a protein. This process is known as translation.
The protein then folds into a specific shape that determines its function in the organism.

The regulation of gene expression refers to the control of the amount and timing of appearance of the functional product of a gene.
Regulating gene expression is crucial because it allows an organism to adapt to its changing environment and to carry out the many processes that occur within a cell.
Gene regulation can occur at many levels: from transcriptional initiation, to RNA processing, and to the post-translational modification of a protein.

Although DNA and RNA both carry genetic material, they are quite different. DNA is double-stranded, while RNA is single-stranded.
The bases in DNA are A, T, C, and G, whereas in RNA, T is replaced by U.
DNA is responsible for storing and transferring genetic information, while RNA directly codes for amino acids and acts as a messenger between DNA and ribosomes to make proteins.