| 单词 | retrovirus | |||
| 释义 | retrovirus ret·ro·vi·rusR0199950 (rĕt′rō-vī′rəs, rĕt′rə-vī′-)retrovirus(ˈrɛtrəʊˌvaɪrəs)ret•ro•vi•rus(ˌrɛ trəˈvaɪ rəs, ˈrɛ trəˌvaɪ-)n., pl. -rus•es. ret·ro·vi·rus(rĕt′rō-vī′rəs)
retrovirusretrovirus,type of RNA virusvirus,parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes. ..... Click the link for more information. that, unlike other RNA viruses, reproduces by transcribing itself into DNA. An enzyme called reverse transcriptase allows a retrovirus's RNA to act as the template for this RNA-to-DNA transcription. The resultant DNA inserts itself into a cell's DNA and is reproduced along with the cell and its daughters. The life cycle is completed when the viral DNA in selected daughter cells makes an RNA copy of itself that covers itself in a protein coat and leaves the cell. Retroviruses sometimes destroy the cells whose DNA they alter, as with HIV, the virus that causes AIDSAIDS or acquired immunodeficiency syndrome, fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981. ..... Click the link for more information. , and sometimes cause them to become cancerous, as with the viruses that cause certain leukemiasleukemia , cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets. ..... Click the link for more information. . Lentiviruses are retroviruses that cause slowly progressing diseases, such as AIDS. RetrovirusA family of viruses distinguished by three characteristics: (1) genetic information in ribonucleic acid (RNA); (2) virions possess the enzyme reverse transcriptase; and (3) virion morphology consists of two proteinaceous structures, a dense core and an envelope that surrounds the core. Some viruses outside the retrovirus family have some of these characteristics, but none has all three. Numerous retroviruses have been described; they are found in all families of vertebrates. See Animal virus, Reverse transcriptase, Ribonucleic acid (RNA) The genome is composed of two identical molecules of single-stranded RNA, which are similar in structure and function to cellular messenger RNA. Deoxyribonucleic acid (DNA) is not present in the virions of retroviruses. The reverse transcriptase in each virus makes a DNA copy of the RNA genome shortly after entry of the virus into the host cell. The discovery of this enzyme changed thinking in biology. Previously, the only known direction for the flow of genetic information was from DNA to RNA, yet retroviruses make DNA copies of their genome by using an RNA template. This reversal of genetic information was considered backward and hence the family name retrovirus, meaning backward virus. Once the DNA copy of the RNA genome is made, it is inserted directly into one of the chromosomes of the host cell. This results in new genetic information being acquired by the host species. The study of reverse transcriptase has led to other discoveries of how retroviruses add a variety of new genetic information into the host. One such class of genes carried by retroviruses is oncogenes, meaning tumor genes. Retroviral oncogenes appear to be responsible for tumors in animals. See Oncogenes, Virus classification Two distinct retroviruses have been discovered in humans. One is human T-cell lymphotropic virus type 1 (HTLV-1), a type C-like virus associated with adult T-cell leukemia. The other is the human acquired immune deficiency syndrome (AIDS) virus, a type E lentivirus. See Acquired immune deficiency syndrome (AIDS) retrovirus[′re·trō‚vī·rəs]retrovirusA virus that is designed to avoid discovery by attacking the virus signatures or the antivirus program attempting to detect it. See virus and antivirus program.retrovirusretrovirus[ret´ro-vi″rus]ret·ro·vi·rus(ret'rō-vī'rŭs),Retroviruses are potent disease agents, but they have also served as invaluable research tools in molecular biology. In 1979, the molecular biologist Richard Mulligan used a genetically altered retrovirus to trigger the production of hemoglobin in vitro by monkey kidney cells. His technique for using retroviruses to import alien genes into cells has been widely adopted. Medical researchers have also explored retroviral transport as a means of gene therapy. However, evidence suggesting that retroviruses may play a role in carcinogenesis raises questions as to the safety of their use in gene therapy. see oncogene. retrovirus(rĕt′rō-vī′rəs, rĕt′rə-vī′-)retrovirusVirology An RNA virus that encodes reverse transcriptase so that its RNA can be transcribed into DNA in a host cell; modified retroviruses are used as vectors to introduce genes–or portions thereof–of interest into eukaryotic cells. See Cloning vector, DNA, Eukaryote, Gene, HIV, HTLV, Reverse transcriptase, RNA, Rous sarcoma virus, Spumavirus, Transciption, Virus.ret·ro·vi·rus(ret'rō-vī'rŭs)retrovirusA virus with a GENOME consisting of a single strand of RNA from which DUPLEX DNA is synthesized under the catalytic influence of an enzyme called reverse transcriptase. This is the reverse of the much more common DNA to RNA process. The AIDS virus HIV is a retrovirus.retrovirusan RNA VIRUS that infects animal CELLS and replicates by first being converted to double-stranded DNA, with the ENZYME REVERSE TRANSCRIPTASE. (Retroviruses are so called because the information flows from RNA to DNA.) The DNA copy of the RNA GENOME so formed integrates into the host's DNA. There is a number of groups of retroviruses, including the spumaviruses, for example the human foamy virus; the lentiviruses, for example HIV; and the oncoviruses (RNA tumour viruses) which are divided into A-type, B-type, C-type and D-type.Retrovirusret·ro·vi·rus(ret'rō-vī'rŭs)See RV retrovirus
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