What is the importance of retroviruses?
The most important advantage that retroviral vectors offer is their ability to transform their single stranded RNA genome into a double stranded DNA molecule that stably integrates into the target cell genome. This means that retroviral vectors can be used to permanently modify the host cell nuclear genome.
What are unique characteristics of retroviruses?
Characteristics. of retroviruses is single-stranded and possesses "positive" polarity similar to that found in messenger RNA (mRNA). Virions (virus particles) contain two 5′ ("five prime"), end-linked, identical copies of the genome RNA, and are therefore said to be diploid.
How is retrovirus different from other viruses?
How are retroviruses different from other viruses? Most RNA viruses reproduce by inserting RNA into the host cell. The RNA contains the instructions for making copies of the virus. A retrovirus is an RNA virus, but instead of inserting the RNA directly into the cell, it first converts it into DNA.
How are retroviruses unique from other types of viruses quizlet?
Terms in this set (30) How are retroviruses different from other types of viruses? - Retrovirus RNA is incorporated into the host cell's DNA in order to be translated. - Retroviruses use the enzyme reverse transcriptase to transcribe a copy of DNA from their own RNA.
What defines a retrovirus?
Listen to pronunciation. (REH-troh-VY-rus) A type of virus that has RNA instead of DNA as its genetic material. It uses an enzyme called reverse transcriptase to become part of the host cells' DNA.
Why are retroviruses important in molecular biology?
Studies of retroviruses have contributed greatly to our understanding of mechanisms that regulate eukaryotic gene expression. In addition retroviruses are proving to be valuable research tools in molecular biology and have been used successfully in gene therapy (e.g. to treat X-linked severe combined immunodeficiency).
Overview
A retrovirus is a type of virus that inserts a copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an
Structure
Virions, viruses in the form of independent particles of retroviruses, consist of enveloped particles about 100 nm in diameter. The outer lipid envelope consists of glycoprotein. The virions also contain two identical single-stranded RNA molecules 7–10 kilobases in length. The two molecules are present as a dimer, formed by base pairing between complementary sequences. Interaction sites …
Multiplication
When retroviruses have integrated their own genome into the germ line, their genome is passed on to a following generation. These endogenous retroviruses (ERVs), contrasted with exogenous ones, now make up 5–8% of the human genome. Most insertions have no known function and are often referred to as "junk DNA". However, many endogenous retroviruses play important roles in ho…
Transmission
• Cell-to-cell
• Fluids
• Airborne, like the Jaagsiekte sheep retrovirus.
Provirus
The DNA formed after reverse transcription (the provirus) is longer than the RNA genome because each of the terminals have the U3 - R - U5 sequences called long terminal repeat (LTR). Thus, 5' terminal has the extra U3 sequence, while the other terminal has the U5 sequence. LTRs are able to send signals for vital tasks to be carried out such as initiation of RNA production or management of the rate of transcription. This way, LTRs can control replication, hence, the entir…
Early evolution
Studies of retroviruses led to the first demonstrated synthesis of DNA from RNA templates, a fundamental mode for transferring genetic material that occurs in both eukaryotes and prokaryotes. It has been speculated that the RNA to DNA transcription processes used by retroviruses may have first caused DNA to be used as genetic material. In this model, the RNA world hypothesis, cellular organisms adopted the more chemically stable DNA when retroviruses evolved to create
Gene therapy
Gammaretroviral and lentiviral vectors for gene therapy have been developed that mediate stable genetic modification of treated cells by chromosomal integration of the transferred vector genomes. This technology is of use, not only for research purposes, but also for clinical gene therapy aiming at the long-term correction of genetic defects, e.g., in stem and progenitor cells. Retroviral vector particles with tropism for various target cells have been designed. Gammaretro…
Cancer
Retroviruses that cause tumor growth include Rous sarcoma virus and mouse mammary tumor virus. Cancer can be triggered by proto-oncogenes that were mistakenly incorporated into proviral DNA or by the disruption of cellular proto-oncogenes. Rous sarcoma virus contains the src gene that triggers tumor formation. Later it was found that a similar gene in cells is involved in cell signaling, which was most likely excised with the proviral DNA. Nontransforming viruses can ran…