retrovirus

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retrovirus,

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.
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 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.
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, 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.
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. Lentiviruses are retroviruses that cause slowly progressing diseases, such as AIDS.

Retrovirus

A 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]
(virology)
A family of ribonucleic acid viruses distinguished by virions which possess reverse transcriptase and which have two proteinaceous structures, a dense core, and an envelope that surrounds the core.

retrovirus

A 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.
References in periodicals archive ?
The annealed oligonucleotides were ligated into the BglII and HindIII sites of the retroviral vector pSuper.
In Spain, 595 heterosexual couples were studied, and none of the HIV-negative partners were infected by a patient taking retrovirals, Hirschel said.
Acute retroviral syndrome and primary HIV infection may be frequently unsuspected by the evaluating clinician because the signs and symptoms are relatively nonspecific.
Gorillas, baboons, and macaques also possessed about 100 retroviral copies.
The genetically engineered retroviruses -- retroviral vectors -- were the way to go.
Retroviral and lentiviral pseudotypes have been employed in lieu of replication-competent virus to study neutralizing antibody responses to viral infection (20,21).
In contrast, no retroviral footprints appeared in the cerebrospinal fluid of 22 individuals with other brain disorders and 30 volunteers who were free of neurological and psychiatric ailments.
Schatten responds that he's not restricting his research to retroviral vectors.
These fibroblasts contain and express endogenous retroviral genomes (1).
M, Retroviral Physician at MGM hospital in Mumbai, India.
Economists explore how the retroviral disease might inhibit commercial development in the region.