| heptad repeat | <molecular biology> A heptad repeat is a type of tandem repeat sequence. It is a sequence of seven amino acids which is repeated multiple times in a row within certain proteins (the intermediate filament proteins) of nearly every animal in the animal kingdom. (09 Oct 1997) |
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| HIV long-terminal repeat | Regulatory sequences important for viral replication that are located on each end of the HIV genome. The ltr includes the HIV enhancer, promoter, and other sequences. Specific regions in the ltr include the negative regulatory element (nre), nf-kappa b binding sites , sp1 binding sites, tata box, and trans-acting responsive element (tar). The binding of both cellular and viral proteins to these regions regulates HIV transcription. (12 Dec 1998) |
| direct terminal repeat | A particular sequence of nucleotides which appears on both ends of a DNA or RNA molecule. (09 Oct 1997) |
| inverted repeat | Either of two copies of a DNA sequence (such as those foundat oppositeends of a transposon) whichoccur in identical but inverted form. (09 Oct 1997) |
| tandem repeat | <molecular biology> Copies of genes repeated one after another along a chromosome: for example the 40S rRNA genes in somatic cells of toads, of which there are about 500 copies. (18 Nov 1997) |
| tandem repeat sequence | <molecular biology> Multiple copies of the same base sequence on a chromosome, used as a marker in physical mapping. (09 Oct 1997) |
| tandem repeat sequences | Multiple copies of the same DNA base sequence on a chromosome; used as a marker in physical mapping of the chromosome. (12 Dec 1998) |
| trinucleotide repeat | <molecular biology> Repetitive part of a genome that may form part of the coding sequence of a gene. The length of such repeats is frequently polymorphic and unstably amplified repeats appear to be the major cause of such genetic diseases as Huntington disease, fragile X syndrome, spinobulbar muscular atrophy and myotonic dystrophy. (18 Nov 1997) |
| long-terminal repeat | <molecular biology> Identical DNA sequences, several hundred nucleotides long, found at either end of transposons and the proviral DNA, formed by reverse transcription of retroviral RNA. They are thought to have an essential role in integrating the transposon or provirus into the host DNA. Long terminal repeats have inverted repeats, that is, sequences close to either end are identical when read in opposite directions. In proviruses the upstream long-terminal repeat acts as a promoter and enhancer and the downstream long-terminal repeat as a polyadenylation site. Acronym: LTR (15 Nov 1997) |
| long terminal repeat sequences | Regions of the RNA genome associated with regulation, integration, and expression of retroviruses. (05 Mar 2000) |
| 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) |