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A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. [2] After invading a 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 (backward).
The replication cycle of a retrovirus entails the insertion ("integration") of a DNA copy of the viral genome into the nuclear genome of the host cell.Most retroviruses infect somatic cells, but occasional infection of germline cells (cells that produce eggs and sperm) can also occur.
An endogenous retrovirus is a retrovirus without virus pathogenic effects that has been integrated into the host genome by inserting their inheritable genetic information into cells that can be passed onto the next generation like a retrotransposon. [8] Because of this, they share features with retroviruses and retrotransposons.
An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. [2] [3] [page needed] Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is
Bacteriophage vectors are also commonly used in molecular biology. [69] For instance, bacteriophage vectors are used in phage-assisted continuous evolution, promoting rapid mutagenesis of bacteria. [70] Although limited to mycobacteriophages and some phages of gram-negative bacteria, bacteriophages can be used for direct cloning. [71]
A provirus does not directly make new DNA copies of itself while integrated into a host genome in this way. Instead, it is passively replicated along with the host genome and passed on to the original cell's offspring; all descendants of the infected cell will also bear proviruses in their genomes. This is known as lysogenic viral reproduction. [2]
Viral double-stranded DNA is then integrated into the host cell genome via viral integrase, an enzyme that allows for viral DNA integration into host DNA. The virus is now referred to as a provirus, which means the gammaretrovirus DNA has integrated into the host cell genome and is now the template for the formation of viral mRNA and genomic ...
Lentivirus is a genus of retroviruses that cause chronic and deadly diseases characterized by long incubation periods, in humans and other mammalian species. [2] The genus includes the human immunodeficiency virus (HIV), which causes AIDS.