| 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) |
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| 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) |
| allelic gene | See: allele, dominance of traits. (05 Mar 2000) |
| antibiotic resistance gene | Genes in a microorganism which confer resistance to antibiotics, for example by coding for enzymes which destroy it, by coding for surface proteins which prevent it from entering the microorganism, or by being a mutant form of the antibiotic's target so that it can ignore it. (09 Oct 1997) |
| autosomal gene | A gene located on any chromosome other than the sex chromosomes (X or Y). (05 Mar 2000) |
| bicoid gene | A group of genes which are important to the proper development of the head and thorax in the embryo of the fruit fly Drosophila melanogaster. (09 Oct 1997) |
| BRCA1 breast cancer susceptibility gene | This mutated (changed) version of the BRCA1 gene makes a person susceptible to developing breast cancer. (12 Dec 1998) |
| calcitonin gene-related peptide | <protein> A second product transcribed from the calcitonin gene. Calcitonin gene related peptide is found in a number of tissues including nervous tissue. It is a vasodilator that may participate in the cutaneous triple response. It is a neuropeptide of 37 amino acids with structural homology to salmon calcitonin. Co-localises with substance P in neurons. It occurs as a result of alternative processing of mRNA from the calcitonin gene. The neuropeptide is widely distributed in neural tissue of the brain, gut, perivascular nerves, and other tissue. The peptide produces multiple biological effects and has both circulatory and neurotransmitter modes of action. In particular, it is a potent endogenous vasodilator. Intracerebral administration leads to a rise in noradrenergic sympathetic outflow, a rise in blood pressure and a fall in gastric secretion. Acronym: CGRP (05 May 2002) |
| cancer susceptibility gene | tumour suppressor gene |
| rab gene | 1. <molecular biology> One of the three main groups of ras like genes specifying small GTP-binding proteins (the others are ras and rho). Rab proteins are involved in vesicular traffic and seem to control translocation from donor to acceptor membranes. 2. <cell biology> Gene family in plants responsive to abscisic acid: encode proteins of 15-17 kD. (18 Nov 1997) |
| variable gene | <molecular biology> Those regions in the amino acid sequence of both the heavy and the light chains of immunoglobulins where there is considerable sequence variability from one immunoglobulin to other of the same class, in contrast to constant sequence (C) regions. The V regions are associated with the antigen binding areas. They contain hypervariable regions of particularly high sequence diversity. (18 Nov 1997) |
| gap gene | <molecular biology> Segmentation genes involved in specifying relatively coarse subdivisions of the embryo. They are expressed sequentially in development between egg polarity genes and pair rule genes. In Drosophila, there are at least three such genes, for example Kruppel. (18 Nov 1997) |
| gene | <cell biology, molecular biology> Originally defined as the physical unit of heredity, it is probably best defined as the unit of inheritance that occupies a specific locus on a chromosome, the existence of which can be confirmed by the occurrence of different allelic forms. Genes are formed from DNA, carried on the chromosomes and are responsible for the inherited characteristics that distinguish one individual from another. Each human individual has an estimated 100,000 separate genes. Given the occurrence of split genes, it might be redefined as the set of DNA sequences (exons) that are required to produce a single polypeptide. (09 Oct 1997) |
| gene activation | The process of activation of a gene so that it is expressed at a particular time. This process is crucial in growth and development. (05 Mar 2000) |
| gene amplification | <molecular biology> Selective replication of DNA sequence within a cell, producing multiple extra copies of that sequence. The best known example occurs during the maturation of the oocyte of Xenopus, where the set (normally 500 copies) of ribosomal RNA genes is replicated some 4,000 times to give about 2 million copies. (18 Nov 1997) |