deoxyribonucleic acid
Meaning of deoxyribonucleic acid: The full chemical name of DNA, and it is descriptive: a sugar missing an oxygen, a nucleus, and an acid.
Definition of deoxyribonucleic acid
Deoxyribonucleic acid, almost always shortened to DNA, is the molecule that carries the genetic instructions for building and running a living organism. It consists of two long strands wound around each other as a double helix, joined down the middle by paired chemical bases and held along the outside by a backbone of sugar and phosphate units.
What does the name describe?
Each word is a piece of chemistry. Nucleic records that the substance was first isolated from the nucleus of cells. Acid refers to the phosphate groups in the backbone, which carry a negative charge and make the molecule acidic. Ribo names ribose, the five-carbon sugar in the backbone, and deoxy records that this sugar is missing one oxygen atom compared with the ribose in the closely related molecule RNA. That single absent oxygen is not a trivial difference: it makes DNA considerably more stable and less easily broken apart, which suits a molecule that must be preserved intact for the life of a cell and passed on.
How is the molecule assembled?
| Part | What it contributes |
|---|---|
| Phosphate | Links one sugar to the next, forming the backbone and its charge |
| Deoxyribose | The sugar each base is attached to |
| Base | Adenine, thymine, guanine or cytosine; the information-carrying part |
One of each makes a nucleotide, the repeating unit of the chain. Bases pair across the helix in fixed combinations, adenine with thymine and guanine with cytosine, so the two strands carry complementary versions of the same information. The strands also run in opposite directions, which is why one end of a strand is described as the five prime end and the other as the three prime end.
How is the information read?
The order of bases along a strand is the message. A stretch of it is copied into RNA, and that copy is read three bases at a time, each triplet specifying one amino acid. Assembling those in order produces a protein, so the base order determines the amino acid sequence and therefore the protein's shape and function. Before a cell divides, the strands separate and each is used as a template to build a new partner, giving two complete copies. Errors introduced during copying, or damage that is not repaired, alter the sequence, and such changes are called mutations.
Also known as
Used in a sentence
Genetic testing analyzed the patient's DNA for a specific inherited mutation.
Good to know
DNA holds the full set of genetic instructions in a stable form, while RNA copied from it carries out shorter-lived tasks such as directing protein production, a difference that determines whether a genetic test examines DNA or RNA.
Word origin
Where “deoxyribonucleic acid” comes from
The name is descriptive: nucleic for the cell nucleus where it was first isolated, acid for the phosphate groups in its backbone, ribo for the sugar ribose, and deoxy for the one oxygen atom that sugar lacks compared with the ribose in RNA.