| DNA, circular | Any of the covalently closed DNA molecules found in bacteria, many viruses, mitochondria, plastids, and plasmids. Small, polydisperse circular DNA's have also been observed in a number of eukaryotic organisms and are suggested to have homology with chromosomal DNA and the capacity to be inserted into, and excised from, chromosomal DNA. It is a fragment of DNA formed by a process of looping out and deletion, containing a constant region of the mu heavy chain and the 3'-part of the mu switch region. Circular DNA is a normal product of rearrangement among gene segments encoding the variable regions of immunoglobulin light and heavy chains, as well as the T-cell receptor. (12 Dec 1998) |
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| DNA cloning | The use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA. (12 Dec 1998) |
| DNA, complementary | Single-stranded complementary DNA synthesised from an RNA template by the action of RNA-dependent DNA polymerase. Cdna (i.e., complementary DNA, not circular DNA, not c-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe. (12 Dec 1998) |
| DNA (cytosine-5-)-methyltransferase | <enzyme> An enzyme that catalyses the transfer of a methyl group from s-adenosylmethionine to the 5-position of cytosine or to the 6-position in adenine in mammalian DNA. Chemical name: S-Adenosyl-L-methionine:DNA (cytosine-5-)-methyltransferase Registry number: EC 2.1.1.37 (12 Dec 1998) |
| DNA damage | Drug- or radiation-induced injuries in DNA that introduce deviations from its normal double-helical conformation. These changes include structural distortions which interfere with replication and transcription, as well as point mutations which disrupt base pairs and exert damaging effects on future generations through changes in DNA sequence. If the damage is minor, it can often be repaired (DNA repair). If the damage is extensive, it can induce apoptosis. (12 Dec 1998) |
| DNA delta-helicase | <enzyme> From foetal calf thymus; partially copurifies with DNA polymerase delta; also has DNA-dependent atpase activity Registry number: EC 3.6.1.- (26 Jun 1999) |
| DNA deoxyribophosphodiesterase | <enzyme> From E coli; catalyses the release of deoxyribose phosphate residues from polydeoxyribonucleotide 5'-termini Registry number: EC 3.1.4.- Synonym: drpase (26 Jun 1999) |
| DNA-dependent ATPase | <enzyme> Factor y is a phage 174 specific DNA-dependent atpase; atpase I can act with double-stranded DNA; atpase II and III require single-stranded DNA; a18r from vaccinia virus Registry number: EC 3.6.1.- Synonym: DNA helicase II, factor y, DNA-dependent atpase I, DNA-dependent atpase II, DNA-dependent atpase III, rep protein (E coli), atpase, DNA-dependent, DNA-dependent atpase iv, uvrd protein, rep helicase, pri a protein, protein n', rip100, pria helicase, pria protein (helicase), a18r gene product, DNA helicase a (26 Jun 1999) |
| DNA-dependent ATPase-endonuclease | <enzyme> Atpase and endonuclease are part of a single protein from phage t4 infected E coli; atpase is activated by duplex, single-stranded or supercoiled DNA Registry number: EC 3.1.21.- Synonym: atpase-endonuclease (26 Jun 1999) |
| DNA diagnosis | <molecular biology> The use of DNA polymorphisms to detect the presence of a disease gene. (09 Oct 1997) |
| DNA diagnostics | Identifying foetuses or infants afflicted with hereditary diseases or conditions, and carriers of recessive disorders by means of DNA analysis. See: DNA markers, familial screening, prenatal screening. Synonym: genetic testing. (05 Mar 2000) |
| DNA-directed RNA polymerase | <enzyme> A group of enzymes that catalyses DNA template-directed extension of the 3'-end of an RNA strand one nucleotide at a time. They can initiate a chain de novo. In eukaryotes, three forms of the enzyme have been distinguished on the basis of sensitivity to alpha-amanitin, and the type of RNA synthesised. Chemical name: Nucleoside-triphosphate:RNA nucleotidyltransferase (DNA-directed) Registry number: EC 2.7.7.6 (12 Dec 1998) |
| DNA-driven reaction | <molecular biology> A lab technique to mark highly-repeated DNA sequences with a radioactive RNA tracer, by having a much larger amount of complementary DNA molecules than radioactive RNA tracer molecules. (09 Oct 1997) |
| DNA duplex | <molecular biology> The double-stranded DNA molecule, which has a double helix (usually right-handed) structure. (09 Oct 1997) |
| DNA entry nuclease | <chemical> Mw 75kda; from membranes of competent bacillus subtilis cells; shows DNA-binding and nuclease activity; believed to be involved in entry of DNA into competent b subtilis cells (26 Jun 1999) |