| DNA filter assay | <molecular biology> A lab technique used to identify the complementary base sequences of DNA. It involves immobilising the DNA on a filter and putting it in a solution that contains radioactively-labelled probe DNA or RNA molecules. (09 Oct 1997) |
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| DNA fingerprint | <molecular biology> The unique pattern of DNA fragments identified by Southern hybridisation (using a probe that binds to a polymorphic region of DNA) or by polymerase chain reaction (using primers flanking the polymorphic region). (09 Oct 1997) |
| DNA fingerprinting | <molecular biology> See restriction fragment length polymorphism. (18 Nov 1997) |
| DNA footprinting | <molecular biology> Technique for identifying the recognition site of DNA binding proteins: See: footprinting. (18 Nov 1997) |
| DNA fragmentation | Endonucleolytic cleavage of genomic DNA into oligonucleosomal fragments at internucleosomal sites. DNA fragmentation along with chromatin condensation are considered the hallmarks of apoptosis. (12 Dec 1998) |
| DNA, fungal | Deoxyribonucleic acid that makes up the genetic material of fungi. (12 Dec 1998) |
| DNA gap | A localised loss of one of the two strands in the double helix of DNA. (05 Mar 2000) |
| DNA gene | <molecular biology> Any of a number of genes found in the bacteria Escherichia coli which makes proteins that are essential for DNA replication. (09 Oct 1997) |
| DNA glycosylase | <enzyme, molecular biology> Class of enzymes involved in DNA repair. They recognise altered bases in DNA and catalyse their removal by cleaving the glycosidic bond between the base and the deoxyribose sugar. at least 20 such enzymes occur in cells. (18 Nov 1997) |
| DNA gyrase | <enzyme, molecular biology> A type II topoisomerase of Escherichia coli, that is essential for DNA replication. This enzyme can induce or relax supercoiling. (18 Nov 1997) |
| DNA helix | The helical structure assumed by two strands of deoxyribonucleic acid, held together throughout their length by hydrogen bonds between bases on opposite strands, referred to as Watson-Crick base pairing. See: base pair. Synonym: DNA helix, double helix, twin helix. (05 Mar 2000) |
| DNA, helminth | Deoxyribonucleic acid that makes up the genetic material of helminths. (12 Dec 1998) |
| DNA homology | <molecular biology> How closely related two or more separate strands of DNA are to each other, based on their base sequences. (09 Oct 1997) |
| DNA hybridisation | <molecular biology> The process of joining two complementary strands of DNA or one each of DNA and RNA to form a double-stranded molecule. Technique in which single stranded nucleic acids are allowed to interact so that complexes or hybrids, are formed by molecules with sufficiently similar, complementary sequences. By this means the degree of sequence identity can be assessed and specific sequences detected. The hybridisation can be carried out in solution or with one component immobilised on a gel or, most commonly, nitrocellulose paper. Hybrids are detected by various means: visualisation in the electron microscope, by radioactively labelling one component and removing noncomplexed DNA or by washing or digestion with an enzyme that attacks single stranded nucleic acids and finally estimating the radioactivity bound. Hybridisations are done in all combinations: DNA DNA (DNA can be rendered single stranded by heat denaturation), DNA RNA or RNA RNA. In situ hybridisations involve hybridising a labelled nucleic acid (often labelled with a fluorescent dye) to suitably prepared cells or histological sections. This is used particularly to look for specific transcription or localisation of genes to specific chromosomes (FISH analysis). <zoology> The mating of individuals from different species or sub-species. (13 Oct 1997) |
| DNA hybridization | A technique used to determine the relatedness of microorganisms by the speed and efficiency of the reassociation of single-stranded DNA to form double-stranded DNA when one of the strands originates from one organism and the other strand from another organism; occurs when the base sequences are complementary or nearly so. (05 Mar 2000) |