| 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) |
|---|---|
| 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) |
| 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) |
| 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) |
| gene bank | A group of genes which are coordinately controlled. (09 Oct 1997) |
| gene cloning | <molecular biology> The insertion of a DNA sequence into a vector that can then be propagated in a host organism, generating a large number of copies of the sequence. (18 Nov 1997) |
| gene cluster | A set of closely related genes that code for the same or similar proteins and which are usuallygrouped together on the same chromosome. (09 Oct 1997) |
| gene conversion | <molecular biology> A phenomenon in which alleles are segregated in a 3:1 not 2:2 ratio in meiosis. May be a result of DNA polymerase switching templates and copying from the other homologous sequence or a result of mismatch repair (nucleotides being removed from one strand and replaced by repair synthesis using the other strand as template). (18 Nov 1997) |
| gene deletion | The total loss (or absence) of a gene. Gene deletion plays a role in birth defects and in the development of cancer. (12 Dec 1998) |
| gene disorder | Hereditary disorder caused by a mutant allele of a single gene (e.g., Duchenne muscular dystrophy, retinoblastoma, sickle cell disease). Compare polygenic disorders. (05 Mar 2000) |
| gene disruption | Use of both in vitro and in vivo recombination to substitute an easily selected mutant gene for a wild-type gene. (09 Oct 1997) |