prophage
enUKpro·phage
P0600000 (prō′fāj′)prophage
(ˈprəʊfeɪdʒ)pro•phage
(ˈproʊˌfeɪdʒ)n.
单词 | prophage |
释义 | prophageenUKpro·phageP0600000 (prō′fāj′)prophage(ˈprəʊfeɪdʒ)pro•phage(ˈproʊˌfeɪdʒ)n. ProphageenUKprophage[′prō‚fāj]Prophagea latent, or occult, noninfectious form of temperate bacteriophage that is present in lysogenic bacteria. Prophage is the deoxyribonucleic acid (DNA) of a temperate bacteriophage combined with the DNA of a lysogenized bacterium. The DNA of a prophage is approximately 1/50 to 1/100 the size of the DNA of a bacterial chromosome and contains about 105 pairs of nucleotides. Thus, a prophage is a complete genome of a phage and contains about 100 genes. A prophage generally occupies a specific locus in a bacterial chromosome and is inherited like ordinary bacterial genes. The prophage of a λ-phage, for example, is localized in a chromosome of colibacillus together with the gene that controls the splitting of galactose. The location of a prophage is genetically controlled by its special region, which constitutes about 1/15 of the total length of the genome. A prophage is nonpathogenic for a bacterial cell and is replicated over many generations simultaneously with the bacterial chromosome. However, in some growing lysogenic bacteria (approximately one cell per million), the prophage becomes infectious, that is, it becomes induced. As a result of induction, it is converted into an intracellular vegetative phage that is not bound to the bacterial chromosome. When this type of phage replicates, the bacterial cell undergoes lysis and dies. Individual lysogenic bacteria may carry several prophages. A. V. KOLOBOV prophageenUKprophage[pro´fāj]pro·bac·te·ri·o·phage(prō'bak-tē'rē-ō-fāj'),prophage(prō′fāj′)pro·bac·te·ri·o·phage(prō'bak-tēr'ē-ō-fāj)Synonym(s): prophage. prophagethe DNA of a BACTERIOPHAGE that is repressed (see GENE REPRESSION) for LYTIC functions and that is maintained in the host bacterium in a stable state. The prophage may be integrated into the DNA of its bacterial host and may be replicated along with the host DNA, as is the case for BACTERIOPHAGE LAMBDA, or may be maintained as EXTRACHROMOSOMAL DNA, as is the case for bacteriophage P1. Prophage DNA may be carried between GENERATIONS (2) in this state and no phage particles are produced. However, the prophage normally retains the ability to direct a lytic cycle, by the activation of genes for lytic development. Upon INDUCTION (3), progeny phages are produced and released from the host. see LYSOGENY. |
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