| DNA sequencing | <molecular biology> Any lab technique used to find out the sequence of nucleotide bases in a DNA molecule or fragment. Examples are dideoxy sequencing and Maxam-Gilbert sequencing. (09 Oct 1997) |
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| gene sequencing | Determination of the sequence of nucleotide bases in a strand of DNA. (14 Nov 1997) |
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| maxam-gilbert sequencing | A lab technique used to find out the sequence of nucleotide bases in a nucleic acid (a DNA or RNA molecule). The technique involves putting copies of the nucleic acid into separate test tubes, each of which contains a chemical that will cleave the molecule at a different base (either adenine, guanine, cytosine, or thymine or uracil (the last depending on whether it is DNA or RNA)). The result is that each of the test tubes contains fragments of the nucleic acid that all end at the same base, but at different points on the molecule where the base occurs. The contents of the test tubes are then separated by size with gel electrophoresis (one gel well per test tube, four total wells), the smallest fragments will travel the farthest and the largest will travel the least far from the well. The sequence can then be determined from the picture of the finished gel by noting the sequence of the marks on the gel and from which well they came from. (09 Oct 1997) |
| Maxim-Gilbert sequencing | <molecular biology> A method of sequencing DNA using dimethyl sulfate and hydrazinolysis. (05 Mar 2000) |
| chemical sequencing | A lab technique used to determine the sequence of nucleotides in a DNA molecule. The DNA molecule is labelled with radioactive phosphorous (chemical element P), cut into fragments, and analysed through electrophoresis. (09 Oct 1997) |
| protein sequencing | Determining the sequence of amino acids in a protein, a process carried out by automated techniques. (14 Nov 1997) |
| sequencing | <molecular biology, procedure> Determination of the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein. (11 Jun 1998) |
| dideoxy sequencing | The most popular method of DNA sequence determination (c.f. Maxam Gilbert sequencing). Starting with single stranded template DNA, a short complementary primer is annealed and extended by a DNA polymerase. The reaction is split into 4 tubes (called A, C, G or T) each containing a low concentration of the indicated dideoxy nucleotide, in addition to the normal deoxynucleotides. Dideoxynucleotides, once incorporated, block further chain extension and so each tube accumulates a mixture of chains of lengths determined by the template sequence. The 4 reactions are denatured and run out on an acrylamide sequencing gel in neighbouring lanes and the sequence read up the gel according to the order of the bands. (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) |