| chromosome pair | Two chromosomes of the full diploid karyotype that are similar in form and function but that usually differ in content, one normally being inherited from each parent and one being transmitted to each progeny; in the heteromorphic sex (in humans, the male), one pair, the sex chromosomes, differ markedly in appearance, content, and function. (05 Mar 2000) |
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| chromosome pairing | The process in synapsis whereby homologous chromosome's align opposite each other before disjoining in the formation of the daughter cell; the apposition permits exchange of genetic material in crossing-over. (05 Mar 2000) |
| chromosome puffs | Expansions of particular chromosome regions; sites of RNA syntheses. (05 Mar 2000) |
| chromosome rosette | Right before metaphase, human chromosomes briefly form this single ring structure. (09 Oct 1997) |
| chromosome rosette john jordan | Right before metaphase, human chromosomes briefly form this single ring structure. (09 Oct 1997) |
| chromosome satellite | A small chromosomal segment separated from the main body of the chromosome by a secondary constriction; in humans it is usually associated with the short arm of an acrocentric chromosome. (05 Mar 2000) |
| chromosome segregation | <cell biology> The orderly separation of one copy of each chromosome into each daughter cell at mitosis. (18 Nov 1997) |
| chromosome synapsis | <cell biology> The close apposition of homologous chromosomes before cell division or permanently in giant polytene chromosomes. (18 Nov 1997) |
| chromosome translocation | <cell biology> The fusion of part of one chromosome onto part of another. Largely sporadic and random, there are some translocations at hot spots that occur often enough to be clinically significant. See: Philadelphia translocation. (18 Nov 1997) |
| chromosome walking | A procedure to find and sequence a gene whose approximate position in a chromosome is known by classical genetic linkage studies. Starting with the known sequence of a gene shown by classical genetics to be near to the novel gene, new clones are picked from a genomic library by hybridisation with a short probe generated from the appropriate end of the known sequence. The new clones are then sequenced, new probes generated and the process repeated until the gene of interest is reached. (18 Nov 1997) |
| Philadelphia chromosome | <genetics, oncology> Characteristic chromosomal abnormality in which a portion of chromosome 22 is translocated to chromosome 9. This abnormality is found in nearly all cases of chronic myeloid leukaemia and some cases of acute lymphoblastic leukaemia. (30 Sep 1997) |
| mitochondrial chromosome | The DNA component of mitochondria, the chief function of which is synthesis of adenosine triphosphate and the management of cellular energy; the chromosome contains some 16,000 base pairs arranged in a circle. The inheritance is matrilineal, and the mutation rate is unusually high; since each cell contains thousands of copies a mutant form may assume an almost continuous gradation as in a galtonian process. Most of the mutations known have their impact on the respiratory chain. (05 Mar 2000) |
| monocentric chromosome | <genetics, molecular biology> Chromosome with a single centromere, i.e. most chromosomes. (18 Nov 1997) |
| w chromosome | <genetics> A sex chromosome found in all birds and certain other animals where the female is the heterogametic sex. The W chromosome causes the individual to become female in bird species. It is part of the WZ set of sex chromosomes, where the female has one W chromosome and one Z chromosome, and the male has two Z chromosomes. (09 Oct 1997) |
| polytene chromosome | <cell biology> Giant chromosomes produced by the successive replication of homologous pairs of chromosomes, joined together (synapsed) without chromosome separation or nuclear division. They thus consist of many up to 1000) identical chromosomes (strictly chromatids) running parallel and in strict register. The chromosomes remain visible during interphase and are found in some ciliates, ovule cells in angiosperms and in larval Dipteran tissue. The best known polytene chromosomes are those of the salivary gland of the larvae of Drosophila melanogaster which appear as a series of dense bands interspersed by light interbands, in a pattern characteristic for each chromosome. The bands, of which there are about 5,000 in Drosophila melanogaster, contain most of the DNA (ca 95%) of the chromosomes and each band roughly represents one gene. The banding pattern of polytene chromosomes provides a visible map to compare with the linkage map determined by genetic studies. Some segments of polytene chromosome show chromosome puffs, areas of high transcription. (18 Nov 1997) |