[Abbr. of deoxyribonucleic acid]
A complex nucleic acid of high molecular weight consisting of nucleotides made of deoxyribose, phosphoric acid, and one of four bases (two purines, adenine [A] and guanine [G], and two pyrimidines, thymine [T] and cytosine [C]). The nucleotides are arranged in a double helix (two long spirals twisting around each other) joined by hydrogen bonds between the complementary base pairs A-T and C-G. Nucleic acid, present in chromosomes of the nuclei of cells, is the chemical basis of heredity and the carrier of genetic information for all organisms except the RNA viruses.

SEE: chromosome; SEE: gene; SEE: RNA; SEE: virus

ancient DNA

Fragments of nucleic acid obtained from decaying or partially preserved cells of extinct organisms, e.g., from archaeological sites or burial grounds.

complementary DNA

A double-stranded copy of a single-stranded RNA molecule, made by reverse transcriptase, an enzyme used by retroviruses such as HIV-1.

covalently closed circular DNA


fecal DNA

Traces of nucleic acids found in the stool of people with colorectal cancers and polyps. Testing for tumor DNA in stool has been proposed as a means of screening for colorectal cancer.
SYN: SEE: stool DNA testing

mitochondrial DNA

ABBR: mtDNA DNA found in mitochondria. It differs from nuclear DNA in its nucleotide sequences, its size (about 16.5 kb), and its source (it is derived solely from the ovum, not the sperm). Variations in mtDNA point to the ways in which members of a related population differ from each other genetically.

naked DNA

DNA that has been modified to remove the proteins that normally surround it. It is used for genetic transfers and vaccine manufacture.

recombinant DNA

Segments of DNA from one organism artificially manipulated or inserted into the DNA of another organism through gene splicing. When the host's genetic material is reproduced, the transplanted genetic material is also copied. Gene splicing permits isolation and examination of the properties and action of specific genes.
SEE: plasmid; SEE: gene splicing

spacer DNA

SEE: Spacer sequence.