| reduction of chromosomes | The process during meiosis whereby one member of each homologous pair of chromosomes is distributed to a sperm or ovum; the diploid set of chromosomes (46 in humans) is thus reduced to the haploid set in each gamete; union of the sperm and ovum then restores the diploid or somatic number in the one-cell zygote. (05 Mar 2000) |
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| ring chromosomes | Aberrant chromosomes with no ends. (12 Dec 1998) |
| chromosomes | The self-replicating genetic structures of cells containing the cellular DNA that bears in its proteins. (09 Oct 1997) |
| chromosomes, archaeal | Structures within the nucleus of archaeal cells consisting of or containing DNA, which carry genetic information essential to the cell. (12 Dec 1998) |
| chromosomes, bacterial | Structures within the nucleus of bacterial cells consisting of or containing DNA, which carry genetic information essential to the cell. (12 Dec 1998) |
| chromosomes, fungal | Structures within the nucleus of fungal cells consisting of or containing DNA, which carry genetic information essential to the cell. (12 Dec 1998) |
| chromosomes in multiple miscarriages | Couples who have had more than one miscarriage (spontaneous abortion) have about a 5% chance that one member of the couple is carrying a chromsome translocation responsible for the miscarriages. (12 Dec 1998) |
| 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) |
| 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) |
| double minute chromosomes | <genetics, molecular biology> Paired, extrachromosomal elements lacking centromeres, often associated with a drug resistance gene. (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) |