| pair production | <physics> The simultaneous production of an electron and a positron by an interaction of a photon or a fast charged particle with the electronic field of a nucleus or other particle. (16 Dec 1997) |
|---|---|
| pair rule gene | <molecular biology> A segmentation gene, expressed sequentially between gap genes and segment polarity genes. In development of Drosophila, a set of about 8 genes that are expressed only in alternate segments (odd or even) of the developing embryo. Loss of function mutants thus lack alternate segments. Examples: even skipped (eve), fushi tarazu (ftz), hairy. (18 Nov 1997) |
| matched-pair analysis | A type of analysis in which subjects in a study group and a comparison group are made comparable with respect to extraneous factors by individually pairing study subjects with the comparison group subjects (e.g., age-matched controls). (12 Dec 1998) |
| 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) |
| conjugate acid-base pair | In prototonic solvents (e.g., H2O, NH3, acetic acid), two molecular species differing only in the presence or absence of a hydrogen ion (e.g., carbonic acid/bicarbonate ion or ammonium ion/ammonia); the basis of buffer action. (05 Mar 2000) |
| nucleotide pair | <molecular biology> Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs. (09 Oct 1997) |
| banding of chromosomes | Treatment of chromosomes to reveal characteristic patterns of horizontal bands. Thanks to these banding patterns that resemble bar codes, each human chromosome is distinctive and can be identified without ambiguity. (12 Dec 1998) |
| 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) |
| 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) |