MadSci Network: Genetics
Query:

Re: Can viruses directly cause a genetic mutation on a strand of DNA

Date: Thu Feb 15 10:51:06 2007
Posted By: Stephanie Levi, Grad student, Molecular Genetics and Cell Biology, University of Chicago
Area of science: Genetics
ID: 1170603846.Ge
Message:

Hi there, This is a great question. Viruses cannot reproduce on their own; they are parasitic in that they need a host to reproduce. From a molecular standpoint, the goal of a virus is to hijack the cell's DNA replication machinery so that instead of reproducing the cell's DNA, it's reproducing the virus' DNA. In the case of viruses for which RNA is the genetic material, the virus first uses an enzyme called reverse transcriptase to make a DNA template that can then be used to reproduce the virus' genetic material. The DNA is subsequently transcribed. If cellular DNA replication is occuring at the time of virus infection, it will be incidental; there are examples of viral genomes integrating into host genomes--the most well known are phage virus genomes integrating into bacterial genomes after infection. However, the cell will not have much of a chance to pass on any mutations that were integrated into the genome since the newly reproduced viruses will kill the cells before the cell can reproduce again. As for transcription and translation, molecularly it is not only likely but planned that the cell's transcription machines (RNA polymerases) and translation machines (ribosomes) will begin using viral DNA/RNA as templates. Random mutations integrated into the genome during the cell's DNA replication cycle are not likely to occur as a result of the presence of the virus--these will still occur at the same rate as they would otherwise. It's just that the machinery is going to be hijacked for viral replication and any mutations that do occur during DNA replication won't make it to being able to create problems because the cell will be killed anyway! Please send another email if you have more questions or if this didn't clear things up for you.


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