Friday, April 1, 2011
So you might ask yourself what is the difference between a virus and a retrovirus? The answer is the function of how each replicates its genetic material. A virus has a single strand of genetic material-either DNA or RNA. A retrovirus consists of a single strand of RNA. Once a retrovirus enters a cell, it collects nucleotides and assembles itself as a double strand of DNA that splices itself into the host's genetic material.Retroviruses contain RNA as the hereditary material in place of the more common DNA. In addition to RNA, retrovirus particles also contain the enzyme reverse transcriptase (or RTase), which causes synthesis of a complementary DNA molecule (cDNA) using virus RNA as a template.
When a retrovirus infects a cell, it injects its RNA into the cytoplasm of that cell along with the reverse transcriptase enzyme. This enzyme copies the viral RNA genome into a single minus strand of DNA. The resulting double stranded DNA is integrated into the chromosomal DNA of the infected cell. The proviral DNA is then transcribed by the cell’s own machinery into RNA, which will be either translated into viral proteins or is packaged into other proteins. Because most retroviruses do not kill their host cells, infected cells can replicate, producing daughter cells with integrated proviral DNA. These daughter cells continue to transcribe the proviral DNA and bud progeny virions.