| DNA topoisomerase | <enzyme, molecular biology> An enzyme capable of altering the degree of supercoiling of double stranded DNA molecules. Various topoisomerases can increase or relax supercoiling, convert single stranded rings to intertwined double stranded rings, tie and untie knots in single stranded and duplex rings, catenate and decatenate duplex rings. Topoisomerase II of E. Coli = gyrase. (18 Nov 1997) |
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| DNA topoisomerase (ATP-hydrolysing) | <enzyme> An ATP-requiring enzyme which, in the presence of magnesium ions, introduces negative supertwists into closed and possibly linear duplex DNA. The enzyme is implicated in DNA replication and transcription. It causes the storage of mechanical strain energy in the superhelical turns of DNA at the expense of ATP hydrolysis. Chemical name: DNA topoisomerase (ATP-hydrolysing) Registry number: EC 5.99.1.3 (12 Dec 1998) |
| topoisomerase | <enzyme> That change the degree of supercoiling in DNA by cutting one or both strands. Type I topoisomerases cut only one strand of DNA, type I topoisomerase of E. Coli (omega protein) relaxes negatively supercoiled DNA and does not act on positively supercoiled DNA. Type II topoisomerases cut both strands of DNA, type II topoisomerase of E. Coli (DNA gyrase) increases the degree of negative supercoiling in DNA and requires ATP. It is inhibited by several antibiotics, including nalidixic acid and ovobiocin. (18 Nov 1997) |
| DNA-directed DNA polymerase | <enzyme> DNA-dependent DNA polymerases found in bacteria, animal and plant cells. During the replication process, these enzymes catalyze the addition of deoxyribonucleotide residues to the end of a DNA strand in the presence of DNA as template-primer. They also possess exonuclease activity and therefore function in DNA repair. Chemical name: Deoxynucleoside-triphosphate:DNA deoxynucleotidyltransferase (DNA-directed) Registry number: EC 2.7.7.7 (12 Dec 1998) |
| A-DNA | A form of DNA in which the helix is right-handed and the overall appearance is short and broad. (05 Mar 2000) |
| a-form DNA | <molecular biology> One of several forms that can be assumed by a double helix. A-DNA is stable in dehydrated conditions. This form is less common than the dominant form found under physiological conditions -- beta-DNA. This form is also assumed by DNA-RNA hybrid helices and by regions of double-stranded RNA. It is a right-handed helix and is a more compact form than beta-DNA. (09 Oct 1997) |
| antisense DNA | <molecular biology> A synthetic DNA strand that is complementary to a particular strand of target DNA with a complementary sequence of bases. This results in preventing expression of the gene encoded. These proteins can be used to selectively turn off production of certain proteins or block viral genetic instructions, by marking them for destruction by cellular enzymes, in order to prevent the building of new virus or the infection of new cells. (14 Nov 1997) |
| apurinic DNA | <molecular biology> A DNA molecule that has lost adenine and guanine, its purine bases. Apurinic DNA can be produced by treating the DNA with acid. (09 Oct 1997) |
| ATP-dependent DNA strand transferase | <enzyme> From human cell nuclei; catalyses strand exchange between homologous DNA sequences; magnesium dependent, requires ATP hydrolysis Registry number: EC 2.7.7.- Synonym: ATP-dep-DNA-str trnsfase (26 Jun 1999) |
| bacteriophage T7 induced DNA polymerase | <enzyme> Complex of two proteins, phage gene 5 protein and E coli thioredoxin Registry number: EC 2.7.7.- Synonym: t7 phage DNA polymerase, sequenase, t7 DNA polymerase, thermo sequenase (26 Jun 1999) |
| base in DNA | A unit of the DNA. There are 4 bases: adenine (A), guanine (G), thymine (T), and cytosine (C). The sequence of bases (for example, CAG) is the genetic code. (12 Dec 1998) |
| beta-DNA | <molecular biology> The normal form of DNA found in organisms, which exists as a right-handed helix. (09 Oct 1997) |
| blunt-end DNA | <molecular biology> A fragment of a DNA molecule in which the ends of both strands are even with each other rather than one strand being longer than the other. (09 Oct 1997) |
| blunt-ended DNA | Double-stranded DNA in which at least one of the ends has no unpaired bases. (05 Mar 2000) |
| vaccines, DNA | Recombinant DNA vectors encoding antigens administered for the prevention or treatment of disease. The host cells take up the DNA, express the antigen, and present it to the immune system in a manner similar to that which would occur during natural infection. This induces humoral and cellular immune responses against the encoded antigens. The vector is called naked DNA because there is no need for complex formulations or delivery agents; the plasmid is injected in saline or other buffers. (12 Dec 1998) |