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1、gene amplification258(alleles). The term gene is sometimes used interchangeably with cistron. gene amplification the selective, repeated replication of a certain gene or genes without a proportional increase in other genes in the genome. It occurs, e.g., in the DNA puffs of Rhynchosciara and some ot
2、her flies and in the amplification of the genes coding for ribosomal RNA (so-called ribosomal DNA) in amphibian oocytes. gene bank an alternative name for gene library. gene cloning sec molecular cloning. gene cluster or gene complex any group of two or more func- tionally related genes that are clo
3、sely linked on a chromo- some. The genes of a gene cluster are often structural genes coding for the enzymes that catalyse the various steps of a metabolic pathway. gene complex an alternative name for gene cluster. gene dosage the number of times a particular gene is present in the genome. gene dup
4、lication the phenomenon, occurring in some higher organisms, in which there is duplication of the DNA se- quences representing particular genes. This process is thought to have played a decisive part in the evolution of these organ- isms, through the occurrence of different mutations in the two dupl
5、icated genes.gene expression the process by which the information carried by a gene or genes becomes manifest as the phenotype. It in- volves transcription of the gene into complementary RNA se- quences and, for structural genes, subsequent translation of mRNA into polypeptide chains and their assem
6、bly into the ul- timate protein products. Gene expression is tightly regulated by promoters, enhancers, and transcription factors. gene frequency a measure of the proportion of an allele in a given population, equal to the number of loci at which a given allele occurs, divided by the total number of
7、 loci at which it could occur. gene library or cloned library or gene bank or shotgun collec- tion a random collection of DNA fragments cloned in a vector (def. 3), and which may include all the genetic information of a particular species. It may be prepared from a variety of sources, including an e
8、xtract of mRNA, in contrast to a geno- mic library which is prepared from genomic DNA. gene mutation any mutation (def. 1) occurring within a single gene. gene pool the sum of the genetic information in the reproduct- ive members of a population of sexually reproducing organ- isms. gene product any
9、of the types of RNA (transcription prod- ucts) or any of the proteins or protein subunits (translation products) synthesized biochemically on the basis of the in- formation encoded in a genome. general acid-catalysis homogeneous catalysis in which the catalysts are various hydron donors (acids). Com
10、pare specific acid-catalysis. general base-catalysis homogeneous catalysis in which the catalysts are various hydron acceptors (bases). Compare spe- cific base-catalysis. generally labelled describing the labelling of a molecule in such a way that a radionuclide may be present at any or all (but not
11、 necessarily all) possible positions. Compare uniformly labelled. general transcription factor any of the proteins whose as- sembly around the TATA box is required for the initiation of transcription of most eukaryotic genes. generate (in mathematics) to conceive a point, line, or surface to be movi
12、ng in a specified way so as to form a line, surface, or solid, respectively. generation 1 the act or process of producing or reproducing, naturally or artificially. 2 the phase in a life cycle that extends from one to the immediately successive reproduction. 3 any group comprising all those members
13、of a population who are equally removed from a common ancestor or from coeval an- cestors.genetic codegeneration of diversity (in immunology) the process by which a large number of variable regions are generated in the immunoglobulins. The stem cell genome contains multiple variants of L-chain V (va
14、riable) and J genes and of the H- chain V, J, and D (diversity) genes. As the stem cells differen- tiate, the maturing lymphocyte constructs particular L and H genes of virtually unique structure by a recombination process that randomly selects one out of each set of gene segments and assembles them
15、, together with a C (for the constant region) gene into a mature H or L gene. This, combined with recomb- inational inaccuracies, somatic point mutations, and the varied combinations of L and H chains found in immunoglobulins re- sults in a repertoire of millions of lymphocytes each with H and L gen
16、es encoding unique molecules. See also immunoglobu- lin. generation time the time between division of a cell and that of its daughter cells, averaged over a whole cell population. gene redundancy the presence in a cell of many copies of a single gene. The multiple copies may be inherited or result from selective gene duplication during development. gene-regulatory protein any protein that binds to a specific DNA sequence to alter the expression of a gene. +genesis comb, form denoting beginning o
