Insertion mutagenesis is mutagenesis of DNA due to insertion of one or more base pairs. Insertion mutagenesis can occur in nature or intentionally created in a laboratory using a virus or transposon. Viral insertiemutagenese
Viral insertion mutagenesis is based on the integration of a DNA sequence into the genome of an organism using a virus. A retrovirus integrates its genetic material at any place in the genome of the cell infected with the virus. This feature of retroviruses makes them very suitable for genetic screens.
Insertion of a retrovirus into the genome of an organism can disrupt nearby genes in different ways. Insertion of the virus into the promoter of a gene may increase and decrease the expression of this gene. Integration of the virus into a gene itself can lead to a non-or otherwise-functioning protein upon transcription. Usually, however, in insertion mutagenesis, no effect will be seen. But a small portion of the DNA consists of genes and insertions in the rest of the DNA often have little effect. Genetic screens
In genetic screen, insertion mutagenesis is used to search for genes that play a role in genetic background diseases. An example of this is the common disease cancer. Often, experimental animals are used in the lab. As mentioned earlier, due to the random integration of the virus, there are often no noticeable effects. However, if multiple experimental animals show tumor formation, sites can be looked into in the genome where the virus is integrated. If these places match the different experimental animals, there is a chance that nearby genes play a role in the formation of the tumors.
In this type of genetic screen, the sequence of the virus is known. Using PCR technologies, we can look into where the virus is integrated into the genome and which genes can be disregarded. In the case of diseases with a genetic background, this way can be sought for mutations in certain genes responsible for the disease.
In the case of cancer, some retroviruses have been developed which are known to cause tumor formation. An example of this is the "Murine Leukaemia Virus" (MuLV) that causes tumors in the lymphatic system in mice within 3-4 months. Another widely used virus is the "Mouse Mammary Tumor Virus" (MMTV), which causes tumors in the breast in mice within 6-18 months.
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