| chromosomes, yeast artificial | Chromosomes in which fragments of exogenous DNA ranging in length up to several hundred kilobase pairs have been cloned into yeast through ligation to vector sequences. These artificial chromosomes are used extensively in molecular biology for the construction of comprehensive genomic libraries of higher organisms. (12 Dec 1998) |
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| miscarriages, multiple, chromosomes in | Couples who have had more than one miscarriage have about a 5% chance that one member of the couple is carrying a chromsome translocation responsible for the miscarriages. (12 Dec 1998) |
| segregation of chromosomes | <cell biology, genetics> The separation of pairs of homologous chromosomes that occurs at meiosis so that only one chromosome from each pair is present in any single gamete. (18 Nov 1997) |
| homologous chromosomes | A pair of chromosomes containing the same gene sequences, each derived from one parent. (12 Dec 1998) |
| sex chromosomes | The homologous chromosomes that are dissimilar in the heterogametic sex. There are the x chromosome, the y chromosome, and the w, z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth bombyx mori, for example). In such cases the w chromosome is the female-determining and the male is zz. (12 Dec 1998) |
| nonhomologous chromosomes | <genetics> Chromosome's that are not members of the same pair. (05 Mar 2000) |
| duplication of chromosomes | A chromosome aberration resulting from unequal crossing over or exchange of segments between two homologous chromosomes; one chromosome of the pair loses a small segment, while the other gains this segment; the chromosome gaining the segment has undergone duplication while its homologue has undergone deletion. See: haemoglobin Lepore. (05 Mar 2000) |
| inversion of chromosomes | A chromosome aberration resulting from a double break in a segment of the chromosome, with end for end rotation of the fragment between the fracture lines, and refusion of the fragments; this results in reversal of the order of genes in that segment. (05 Mar 2000) |
| yeast artificial chromosomes | Yeast DNA sequences that have incorporated into them very large foreign DNA fragments; the recombinant DNA is then introduced into the yeast by transformation; the use of yeast artificial chromosomes permits the cloning of large genes with their flanking regulatory sequences. (05 Mar 2000) |
| bufadienolides (two double bonds) | Bufatrienolides (three double bonds), etc; they have varying numbers of hydroxyl groups at positions 3, 5, 14, and 16, and these may be further substituted. For structure, see steroids. (05 Mar 2000) |
| bufenolides (one double bond) | (05 Mar 2000) |
| carbon-carbon double bond isomerases | <enzyme> Enzymes that catalyze the shifting of a carbon-carbon double bond from one position to another within the same molecule. Registry number: EC 5.3.3 (12 Dec 1998) |
| RNA, double-stranded | RNA consisting of two strands as opposed to the more prevalent single-stranded RNA. most of the double-stranded segments are formed from transcription of DNA by intramolecular base-pairing of inverted complementary sequences separated by a single-stranded loop. Some double-stranded segments of RNA are normal in all organisms. (12 Dec 1998) |
| conjugated double bonds | Two or more double bond separated by each single bond. (05 Mar 2000) |
| prospective, randomised, double-blind clinical trial | <statistics> A clinical trial in which the method for analysing data has been specified in the protocol before the study has begun (prospective), the patients have been randomly assigned to receive either the study drug or alternative treatment, and in which neither the patient nor the physician conducting the study know which treatment is being given to the patient. (13 Nov 1997) |