| repetitive DNA | <molecular biology> Nucleotide sequences in DNA that are present in the genome as numerous copies. Originally identified by the C0t_ value derived from kinetic studies of DNA renaturation. These sequences are not thought to code for polypeptides. One class of repetitive DNA, termed highly repetitive DNA, is found as short sequences, 5-100 nucleotides, repeated thousands of times in a single long stretch. It typically comprises 3-10% of the genomic DNA and is predominantly satellite DNA. Another class, which comprises 25-40% of the DNA and termed moderately repetitive DNA, usually consists of sequences about 150 to 300 nucleotides in length dispersed evenly throughout the genome and includes Alu sequences and transposons. (18 Nov 1997) |
|---|---|
| replication, DNA | A wondrous complex process whereby the ( parent ) strands of DNA in the double helix are separated and each one is copied to produce a new ( daughter ) strand. This process is said to be semi-conservative since one of each parent strand is conserrved and remains intact after replication has taken place. (12 Dec 1998) |
| melting temperature of DNA | That temperature at which, under a given set of conditions, double-stranded DNA is changed (50%) to single-stranded DNA; under standard conditions, the base composition of the DNA can be estimated from the denaturation temperature, since the greater the denaturation temperature, the greater the guanine-plus-cytosine content (i.e., GC content) of the DNA. Synonym: melting temperature of DNA. (05 Mar 2000) |
| chimeric DNA | <molecular biology> A molecule of DNA that has resulted from recombination, or has resulted from DNA from two sources being spliced together. (05 Jan 1998) |
| chloroplast DNA | <molecular biology> A circular molecule of DNA found in all photosynthetic plants which codes for the function of photosynthesis. (09 Oct 1997) |
| circular DNA | <molecular biology> C.f. Linear DNA. Examples: plasmids, bacterial, mitochondrial, chloroplast and some viral genomes. (18 Nov 1997) |
| cloning, DNA | The use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA. (12 Dec 1998) |
| molecules, recombinant DNA | A combination of DNA molecules of different origin that are joined using recombinant DNA technology. (12 Dec 1998) |
| competitor DNA | DNA from a test organism that is denatured and then used in in vitro hybridization experiments in which it competes with DNA (homologous) from a reference organism; used to determine the relationship of the test organism to the reference organism. (05 Mar 2000) |
| complementary DNA | <molecular biology> DNA that is synthesised from a messenger RNA template, the single-stranded form is often used as a probe in physical mapping to locate the gene or can be cloned in the double stranded form. Viral reverse transcriptase can be used to synthesise DNA that is complementary to RNA (for example an isolated mRNA). Acronym: cDNA (13 Nov 1997) |
| complementary DNA cloning | <molecular biology, technique> A lab technique where a double-stranded cDNA molecule (or dscDNA) is inserted into a cloning vector (another DNA molecule which will continue to be capable of replication after insertion of foreign material), so that the gene encoded by the cDNA can be expressed (transcribed and used) or so many copies of the gene can be made. (09 Oct 1997) |
| complementary DNA library | <molecular biology> A collection of all of the mRNA molecules present in a cell or organism, all turned into cDNA molecules with the enzyme reverse transcriptase, then inserted into vectors (other DNA molecules which can continue to replicate after addition of foreign DNA). The library can then be probed for the specific cDNA (and thus mRNA) of interest. (09 Oct 1997) |
| covalently closed circular DNA | <molecular biology> A circular molecule of double-stranded DNA which is supercoiled, or coiled up on itself due to internal tensions, because there are no breaks in the phosphate backbone (upon which the nucleotide bases are mounted) to relieve the tensions and allow it to form an open circle. (09 Oct 1997) |
| cytosine-DNA glycosidase | <enzyme> Acts on uv-irradiated DNA at modified cytosine residues which are not pyrimidine dimers Registry number: EC 3.2.2.- Synonym: cytosine-DNA glycosylase (26 Jun 1999) |
| hemimethylated DNA | <molecular biology> Duplex DNA where only one of the two strands are methylated and is important for regulating and protecting DNA. (13 Nov 1997) |