DNA, short for deoxyribonucleic acid, stands as the fundamental hereditary material in humans and virtually all other living organisms. Remarkably, nearly every cell within an individual’s body houses the same DNA blueprint. While the majority of DNA resides in the cell’s nucleus – termed nuclear DNA – a smaller fraction is also present in the mitochondria, known as mitochondrial DNA (mtDNA). Mitochondria are essential cellular components responsible for converting energy from food into a usable form for cells.
Mitochondria are the energy converters within cells and contain mitochondrial DNA.
The information encoded within DNA is structured as a code composed of four distinct chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA comprises approximately 3 billion of these bases, with over 99 percent of them being identical across all individuals. The specific order, or sequence, of these bases dictates the genetic instructions for building and maintaining an organism. This is analogous to how letters of the alphabet are arranged to form meaningful words and sentences.
These DNA bases engage in pairing arrangements: adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). These pairings form units called base pairs. Each base is also linked to a sugar molecule and a phosphate molecule. Collectively, a base, sugar, and phosphate constitute a nucleotide. Nucleotides are organized into two extended strands that twist around each other, creating a spiral configuration known as a double helix. The double helix structure resembles a ladder, where the base pairs act as the ladder’s rungs, and the sugar and phosphate molecules form the vertical sidepieces.
A crucial characteristic of DNA is its capacity to replicate, or create copies of itself. Each strand within the double helix can serve as a template for duplicating the sequence of bases. This replication process is vital during cell division, ensuring that each new cell inherits an exact copy of the DNA from the parent cell.
